Progress 05/31/13 to 05/30/18
Outputs
Progress Report Objectives (from AD-416): Objective 1: Engineer improved photosynthetic efficiency in food, feed, and biofuel crops for improved yields. 1.1 Determine the optimal chlorophyll (Chl) content to maximize the daily integral of canopy photosynthesis. 1.2 Decrease photorespiration by improving the effectiveness of engineered chloroplast photorespiratory bypass pathways by lowering the activity of the chloroplast glycolate exporter. Objective 2: Define the key posttranslational regulatory factors controlling assimilation/partitioning and growth in crop plants. 2.1 Investigate historical and diverse soybean germplasm to study fundamental interactions and constraints between carbon and nitrogen metabolism, and their influence on soybean yield and seed quality. 2.2 Characterize the brassinosteroid (BR) receptor kinase, BRI1, and identify phosphosites that can be manipulated by directed mutagenesis to alter kinase activity or specificity. 2.3 Identify protein interactors with key receptor kinases with specific attention to those where the interaction is phosphorylation dependent and/ or plays a regulatory role. Objective 3: Determine the major features, physiological and genetic, and the mechanistic basis for the response of crops to elevated atmospheric CO2 and tropospheric ozone, and determine their interactions with temperature and drought. 3.1 Investigate the response of growth, photosynthesis and carbohydrate metabolism to elevated CO2 in species with different phloem loading strategies. 3.2 Use functional genomic and quantitative genetic approaches to dissect the genetic basis for ozone tolerance in crops. 3.3 Investigate and compare the physiological and agronomic responses of maize and soybean to heat waves. Objective 4: Determine the linkages between whole plant, physiological and genetic, and ecosystem processes to maximize key ecosystem services for current and alternative bioenergy production systems in the context of carbon, water, and nutrient cycling and energy partitioning. 4.1 Investigate the benefits associated with improving photosynthetic efficiency and/or light attenuation through crop canopies that extend beyond higher productivity. 4.2 Model the regional impacts of improved carbon uptake, carbon sequestration in soils, greenhouse gas emissions, and canopy water use on local- and regional-scale biogeochemical cycles using coupled biosphere- atmosphere-hydrology models. 4.3 Investigate through field measurements and mechanistic ecosystem models the impact of land-use change to accommodate bioenergy feedstock species on regional productivity and ecosystem services. Approach (from AD-416): The overall goal of this research is to identify molecular, biochemical, and genetic determinants of photosynthate production and distribution in crop plants and to utilize this new information to address specific agricultural problems of national importance including those associated with atmospheric change. The experimental approaches are diverse combining biophysics, biochemistry, physiology, molecular biology, and genomics with both laboratory and field components. The approaches used to meet the goals of Objective 1 for improving photosynthetic efficiency of crop plants will center on developing a canopy light energy distribution and two separate strategies to lower soybean leaf chlorophyll. Objective 2 that seeks to key regulatory steps controlling assimilation, partitioning and growth will be approached using a "common garden" experiment with historical soybean cultivars, site directed mutagensis of phytohormone receptors and yeast two-hybrid procedures to find interacting partners of the receptors. Objective 3 involves determining factors controlling the response of crops to global change factors will use Free Air Concentration Enrichment technology (FACE) to impose interacting treatments in a replicated factorial experimental design under field conditions. Objective 4 is intended to discover linkages that scale from leaves to ecosystem responses where the approach relies centrally on large scale flux measurements by eddy covariance technologies. This project made significant advancements toward engineering improved photosynthetic efficiency in crops, defining key post-translational regulatory factors controlling assimilation and partitioning in crops, understanding of the mechanistic basis for crop responses to global climate changes and improving ecosystem and regional models to predict the biogeochemical consequences of global change. Key improvements in photosynthetic efficiency that were studied included reducing chlorophyll content and photorespiration in C3 crops. Research determined that soybean over-invests in chlorophyll and that reduced chlorophyll content in leaves lead to higher light use efficiency, demonstrating that internal reallocation of resources away from chlorophyll could benefit agricultural productivity. Research discovered a novel chloroplast glycolate transporter important for photorespiration, which could accelerate efforts to reduce photorespiration in plants. Studies further determined the cost of photorespiration on yield of U.S. crops, and developed quantitative methods to evaluate synthetic photorespiratory bypass pathways. Progress in defining regulatory factors controlling assimilation and partitioning in crops came from identifying the functional role of phosphorylation sites on important receptor kinases that initiate plant growth, and demonstrating that manipulation of regulatory sites impacts both growth and sensitivity to pathogens. Research also determined the physiological basis for yield improvement in historical soybean varieties, showing that increased harvest index, greater light use efficiency and photosynthesis were important for historical yield gains. Research identified significant genetic variation in soybean response to elevated [CO2] and the physiological basis for differences in response. Studies identified parent lines for the development of a mapping population to identify genes and QTLs associated with CO2 response, and traits correlated with CO2 responsiveness in soybean. Further work identified genetic variation in legume and maize response to ozone, as well as genes associated with ozone response. Research identified specific targets for biotechnological improvement of crop response to ozone, and parental lines for mapping maize tolerance in elevated ozone. Improved ecosystem and regional models to predict the biogeochemical consequences of large-scale land use changes and altered photosynthetic efficiencies were developed. These model tools provide a framework to make informed decisions related to maximizing agricultural outputs for food or biofuel in the context of maximizing soil carbon and water use efficiency. Accomplishments 01 Elevated ozone reduces photosynthetic carbon gain by accelerating leaf senescence of inbred and hybrid maize. Ground-level ozone pollution is estimated to cost U.S. maize farmers up to 10% of potential yields. Yet, the physiological effects of elevated ozone on maize are not well understood. In this study ARS scientists in Urbana, Illinois, and collaborators from University of Illinois and University of Florida examined 10 diverse inbred and 8 diverse hybrid lines for ozone response. Maize was grown at ambient and elevated ozone concentrations under fully open air conditions using Free Air gas Concentration Enrichment (FACE) technology. On average, growth at elevated ozone decreased photosynthesis in both inbreds and hybrids, and there was significant genetic variation in the degree of ozone-induced damage. Lower photosynthetic rates were associated with lower capacity for photosynthesis and not with variation in stomatal conductance. By testing a diverse panel of maize genotypes under field conditions in the world�s primary area of production, this study provides a foundation on which to investigate the genetic variation in maize oxidative stress tolerance, and begin to develop more stress tolerant germplasm. 02 Phloem loading as a driver of plant responses to elevated carbon dioxide concentrations. Phloem loading is the process in which photoassimilates and other nutrients are transported from mesophyll cells into minor vein phloem, and is a major determinant of carbon partitioning and nutrient distribution in plants. It is also associated with flexibility in plants� ability to acclimate to changing environmental conditions. Plants use different mechanisms for loading sucrose and other sugars into the phloem, and it is unknown if species with different phloem loading strategies respond differently to rising carbon dioxide concentrations. ARS researchers in Urbana, Illinois and University of Illinois scientists used meta-analysis and experiments to tested species with different phloem loading strategies for the response of photosynthesis to elevated carbon dioxide concentration. While the quantitative evaluation of literature supported differences in CO2 response among species with different phloem loading strategies, side-by-side experiments did not. Thus, there is not strong experimental evidence for fundamental differences in species' responses to elevated carbon dioxide concentration based on phloem loading strategy. Greater understanding of interspecific variation in plant responses to rising [CO2] is critical for modeling future plant productivity and for identifying targets for crop improvement. 03 Physiological and transcriptomic responses in the seed coat of field- grown soybean (Glycine max L. Merr.) to abiotic stress. Understanding how intensification of abiotic stress due to global climate change affects crop yields is important for continued agricultural productivity. Coupling genomic technologies with physiological crop responses in a dynamic field environment is an effective approach to dissect the mechanisms underpinning crop responses to abiotic stress. ARS researchers in Urbana, Illinois and University of Illinois scientists investigated the genomic response of the soybean seed coat, a tissue that regulates carbon and nitrogen flow to developing seeds, in plants grown in the field under ozone, high temperature or drought stress. All three of those environmental stresses reduced soybean photosynthesis and productivity, but only high temperature stress led to significant changes in expression of key genes. In particular, genes involved in DNA replication and cellular metabolism were altered under high temperature stress, suggesting that a key effect of growth at elevated temperatures is acceleration of developmental progression. This work identifies a new target for plant scientists to engineer in order to improve soybean tolerance to rising temperature stress. Greater tolerance to high temperature stress will benefit U.S. soybean growers. 04 Conversion of grazed pastures to energy cane as a biofuel feedstock alters the emission of greenhouse gasses from soils in Southeastern United States. Bioenergy production is likely to lead to changes in how land is used. Pastures on high organic soils in the subtropics are presently used for primarily grazing, however, the economics of bioenergy feedstock production, for example sugar cane bred for bioenergy production, may favor conversion of this land. Before this can occur, it is important to understand how changing land from grazed pastures to bioenergy sugar cane production will impact productivity as well as other important components of ecosystem function. In this experiment, ARS scientists in Urbana, Illinois, analyzed how changing the land to bioenergy feedstocks in Central Florida would impact the rate in which greenhouse gases, which have a net impact on warming the global and changing climate patterns, will change. The research showed two important results � first that the measured release of greenhouse gases was greater than what was predicted using models; and removing grazed pastures and planting bioenergy sugar cane resulted in greater increases in greenhouse gases than if the land was to remain in grazed pastures. Additionally, the release of greenhouse gases was highly variable, but was linked to fertilization or precipitation. However, these this experiment was limited to transition phase from grazed pastures to bioenergy sugar cane, so long-term responses might vary from our observations. These results will help to assess agronomic strategies that can potentially minimize the impact of agriculture on the local and regional environment. 05 Grazing alters net ecosystem carbon fluxes and the global warming potential of a subtropical pasture. Cattle grazing in subtropical and tropical grassland impacts ecosystem carbon (C) budgets through disturbance, grazing, and inputs associated with manure deposits, but these impacts have never been quantified despite these grasslands account for a substantial portion of global C storage. This experiment investigated how cattle grazing influences the movement of two important gases associated with ecosystem carbon cycling, the transfer of carbon dioxide and methane between the ecosystem and the atmosphere. ARS scientists in Urbana, Illinois, made measurements simultaneously in a grazed pasture, and in an adjacent non-grazed pasture over three years. Grazing increased soil wetness but did not affect soil temperature. Grazing decreased ecosystem respiration, the loss of carbon from the ecosystem, and photosynthesis, the gain of carbon into the ecosystem, because of loss of plant material by the grazers. Loss in respiration was larger than loss in photosynthesis causing grazing to consistently increase the amount of carbon into the ecosystem. The results suggest that the interactions between grazers and soil water affecting soil methane emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased methane loss emissions and removed aboveground biomass, it increased the net storage of carbon and decreased ability of these ecosystems to contribute to global warming. These results provide a mechanistic understanding of how grazing impacts agroecosystem carbon cycling and will help to constrain global models linking agriculture, management, and ecosystem functioning. 06 Consensus, uncertainties and challenges for perennial bioenergy crops and land use. Renewable energy sources are becoming increasingly important to pursue for many reasons including energy security, rural economics, and environmental benefits. Perennial bioenergy crops have significant potential to reduce greenhouse gas (GHG) emissions by removing the need for increased use of fossil fuels. Yet delivering significant GHG savings will require substantial land-use change, globally. Over the last decade, a great deal of research has led to interesting discoveries that can help understanding of the environmental benefits and risks of using perennial bioenergy crops. To assess the most cost-effective and sustainable options for deployment, these discoveries need to be compiled. ARS scientists in Urbana, Illinois, summarized published research on bioenergy land-use change from many different experiments and identified areas of consensus, key uncertainties, and research priorities. This review shows that the direct impacts bioenergy crops on soil carbon and nitrous oxide are increasingly well understood, and are often consistent with significant lifecycle GHG mitigation from bioenergy relative to conventional energy sources. The perennial bioenergy crops will often reduce greenhouse gas emissions, and thus warming. The research also shows there is a mature and increasingly comprehensive evidence base on the environmental benefits and risks of bioenergy cultivation which can support the development of a sustainable bioenergy industry.
Impacts
(N/A)
Publications
- Jin, Z., Ainsworth, E.A., Leakey, A., Lobell, D.B. 2017. Increasing drought will diminish the benefits of elevated carbon dioxide for soybean yields across the US Midwest. Global Change Biology. 24(2):e522-e533. doi. org/10.1111/gcb.13946.
- Yendrek, C.R., Erice, G., Montes, C.M., Tomaz, T., Sorgini, C., Brown, P.J. , McIntyre, L.M., Leakey, A.D.B., Ainsworth, E.A. 2017. Elevated ozone reduces photosynthetic carbon gain by accelerating leaf senescence of inbred and hybrid maize in a genotype-specific manner. Plant Cell and Environment. 40:3088-3100.
- Leisner, C.P., Yendrek, C.R., Ainsworth, E.A. 2017. Physiological and transcriptomic responses in the seed coat of field-grown soybean (Glycine max L. Merr.) to abiotic stress. Biomed Central (BMC) Plant Biology. 17:242.
- Gomez-Casanovas, N., Delucia, N.J., Hudiburg, T.W., Bernacchi, C.J., Delucia, E. 2018. Conversion of grazed pastures to energy cane as a biofuel feedstock alters the emission of GHGs from soils in Southeastern United States. Biomass and Bioenergy. 108:312-322.
- Kirpich, A., Ainsworth, E.A., Wedow, J.M., Newman, J., Michalidis, G., McIntyre, L.M. 2018. Variable selection in omics data: a practical evaluation of small sample sizes. PLoS One. 13(6):e0197910.
- Bishop, K.A., Lomonnier, P., Quebedeaux, J.C., Montes, C.M., Leakey, A.D.B. , Ainsworth, E.A. 2018. Similar photosynthetic response to elevated carbon dioxide concentration in species with different phloem loading strategies. Photosynthesis Research.
- Wang, P., Marsch, E.L., Ainsworth, E.A., Leakey, A.D.B., Sheflin, A.M., Schachtman, D.P. 2017. Shifts in microbial communities in soil, rhizosphere and roots of two major crop systems under elevated CO2 and O3. Scientific Reports. 7:15109.
- Bender, K.W., Zielinski, R.E., Huber, S.C. 2018. Revisiting paradigms of calcium signaling protein kinase regulation in plants. Biochemical Journal. 475(1):202-223.
- Gomez-Casanovas, N., Delucia, N.J., Bernacchi, C.J., Boughton, E., Sparks, J.P., Chamberlain, S.D., Delucia, E.H. 2018. Grazing alters net ecosystem C fluxes and the global warming potential of a subtropical pasture. Ecological Applications. 28(2):557-572.
- Whitaker, J., Field, J.L., Bernacchi, C.J., Cerri, C., Ceulemans, R., Davies, C.A., DeLucia, E.H., Donnison, I.S., McCalmont, J.P., Paustian, K., et al. 2018. Consensus, uncertainties and challenges for perennial bioenergy crops and land use. Global Change Biology Bioenergy. 10(3):150- 164.
- Walker, B., Drewry, D.T., Slattery, R.A., Vanloocke, A., Cho, Y.B., Ort, D. R. 2018. Chlorophyll can be reduced in crop canopies with little penalty to photosynthesis. Plant Physiology. 176(2):1215-1232.
- Moffett, A.S., Bender, K.W., Huber, S.C., Shukla, D. 2017. Allosteric control of a plant receptor kinase through S-glutathionylation. Biophysical Journal. 113(11):2354-2363.
- Mills, G., Sharps, K., Simpson, D., Pleijel, H., Broberg, M., Uddling, J., Jaramillo, F., Davies, W.J., Dentener, F., van den Berg, M., Ainsworth, E. A. et al. 2018. Ozone pollution will compromise efforts to increase global wheat production. Global Change Biology. 24(8):3560-3574.
- Ainsworth, E.A., Lemonnier, P. 2018. Phloem function: A key to understanding and manipulating plant responses to rising atmospheric [CO2]? Current Opinion in Plant Biology. 43:50-56.
- Song, Q., Ort, D.R., Zhu, X. 2017. The impact of modifying antenna size of photosystem II on canopy photosynthetic efficiency � development of a new canopy photosynthesis model scaling from metabolism to canopy level processes. Plant Cell and Environment. 40(12):2946-2957. doi: 10.1111/pce/ 13041.
- Miao, G., Guan, K., Yang, X., Bernacchi, C.J., Berry, J.A., DeLucia, E., Wu, J., Moore, C.E., Meacham, K., Cai, Y., Peng, B., Kimm, H., Masters, M. D. 2018. Sun-induced chlorophyll fluorescence, photosynthesis, and light use efficiency of a soybean field from seasonally continuous measurements. Journal of Geophysical Research-Biogeosciences. 123(2):610-623.
|
Progress 10/01/16 to 09/30/17
Outputs
Progress Report Objectives (from AD-416): Objective 1: Engineer improved photosynthetic efficiency in food, feed, and biofuel crops for improved yields. 1.1 Determine the optimal chlorophyll (Chl) content to maximize the daily integral of canopy photosynthesis. 1.2 Decrease photorespiration by improving the effectiveness of engineered chloroplast photorespiratory bypass pathways by lowering the activity of the chloroplast glycolate exporter. Objective 2: Define the key posttranslational regulatory factors controlling assimilation/partitioning and growth in crop plants. 2.1 Investigate historical and diverse soybean germplasm to study fundamental interactions and constraints between carbon and nitrogen metabolism, and their influence on soybean yield and seed quality. 2.2 Characterize the brassinosteroid (BR) receptor kinase, BRI1, and identify phosphosites that can be manipulated by directed mutagenesis to alter kinase activity or specificity. 2.3 Identify protein interactors with key receptor kinases with specific attention to those where the interaction is phosphorylation dependent and/ or plays a regulatory role. Objective 3: Determine the major features, physiological and genetic, and the mechanistic basis for the response of crops to elevated atmospheric CO2 and tropospheric ozone, and determine their interactions with temperature and drought. 3.1 Investigate the response of growth, photosynthesis and carbohydrate metabolism to elevated CO2 in species with different phloem loading strategies. 3.2 Use functional genomic and quantitative genetic approaches to dissect the genetic basis for ozone tolerance in crops. 3.3 Investigate and compare the physiological and agronomic responses of maize and soybean to heat waves. Objective 4: Determine the linkages between whole plant, physiological and genetic, and ecosystem processes to maximize key ecosystem services for current and alternative bioenergy production systems in the context of carbon, water, and nutrient cycling and energy partitioning. 4.1 Investigate the benefits associated with improving photosynthetic efficiency and/or light attenuation through crop canopies that extend beyond higher productivity. 4.2 Model the regional impacts of improved carbon uptake, carbon sequestration in soils, greenhouse gas emissions, and canopy water use on local- and regional-scale biogeochemical cycles using coupled biosphere- atmosphere-hydrology models. 4.3 Investigate through field measurements and mechanistic ecosystem models the impact of land-use change to accommodate bioenergy feedstock species on regional productivity and ecosystem services. Approach (from AD-416): The overall goal of this research is to identify molecular, biochemical, and genetic determinants of photosynthate production and distribution in crop plants and to utilize this new information to address specific agricultural problems of national importance including those associated with atmospheric change. The experimental approaches are diverse combining biophysics, biochemistry, physiology, molecular biology, and genomics with both laboratory and field components. The approaches used to meet the goals of Objective 1 for improving photosynthetic efficiency of crop plants will center on developing a canopy light energy distribution and two separate strategies to lower soybean leaf chlorophyll. Objective 2 that seeks to key regulatory steps controlling assimilation, partitioning and growth will be approached using a "common garden" experiment with historical soybean cultivars, site directed mutagensis of phytohormone receptors and yeast two-hybrid procedures to find interacting partners of the receptors. Objective 3 involves determining factors controlling the response of crops to global change factors will use Free Air Concentration Enrichment technology (FACE) to impose interacting treatments in a replicated factorial experimental design under field conditions. Objective 4 is intended to discover linkages that scale from leaves to ecosystem responses where the approach relies centrally on large scale flux measurements by eddy covariance technologies. Understanding the mechanisms that control the activity and specificity of important photosynthetic enzymes and processes is foundational to identifying approaches to engineer crop plants with improved agronomic traits. Significant progress has been made understanding the complex regulation photosynthetic enzyme, Rubisco activase, the role of leaf chlorophyll content in optimizing canopy light distribution, the potential of synthetic pathways to improve the energy costs of photorespiration and how protein kinases participate signaling pathways controlling plant growth and development. The understanding of the interactions of crop photosynthetic carbon gain to elements of global climate change is critical to acclimating crops to the rapidly approaching environmental change. Important advances were made quantifying the response of soybean to the interactions of elevated atmospheric carbon dioxide and elevated temperature as well as the underlying genomic basis for variation in the sensitivity of soybean and maize cultivars to ozone. Accomplishments 01 Expression of cyanobacterial fructose-1,6/sedoheptulose-1,7- bisphosphatase (FBP/SBPase) in soybean prevents yield depression under future climate conditions. Researchers from ARS, the University of Illinois Urbana-Champaign, and the University of Nebraska � Lincoln investigated the impact atmospheric warming and elevated CO2 on photosynthesis, growth and yields of soybean lines that have been genetically modified to adapt to these future-predicted conditions. Results showed that overexpressing key Photosynthetic Carbon Reduction Cycle enzymes increased photosynthetic rates at high light, high temperatures, and high CO2 concentrations. This response provided protection of soybean yield to higher temperatures with the genetically modified plants not showing the decreased yield response typically observed at high temperatures. This study outlines the challenges associated with higher temperature and rising CO2 on crop production but also provides one opportunity to adapt crops to challenging growth environments. 02 The influence of drought-heat stress on long-term carbon fluxes of bioenergy crops grown in the Midwestern US. Researchers from ARS and the University of Illinois, Urbana, Illinois investigated influence of a natural drought on the carbon and water cycling within traditional row crops and perennial biomass grass species. The data set that was analyzed resulted from an experiment, which began in 2008, continued through the significant Midwestern drought of 2012 as well as through the 2013 recovery. The 2017 analysis of this data set showed that while the maize and soybean crops showed a significant reduction in carbon uptake and eventual loss in water use due to limited soil moisture supply, the perennial grasses maintained higher productivity and water use throughout the drought due to deeper established rooting profiles. Despite the higher level of productivity during the drought, the perennial grasses showed lower water use efficiency, likely as a result of access to soil moisture coupled with extremely dry atmospheric conditions, and further showed a lag effect on productivity the following year (2013) due to a lack of soil moisture recharge. There was no apparent lag effect on the annual crops. This study outlines that while perennial crops show resilience during extreme drought conditions, there are consequences of higher water use during a drought that can negatively impact productivity in following years. 03 High-throughput phenotyping of maize leaf physiological and biochemical traits using hyperspectral reflectance. The capacity to measure physiological traits in thousands of crop genotypes in a field environment is constrained by available high-throughput phenotyping platforms. ARS and University of Illinois scientists in Urbana, Illinois provided proof of concept for high-throughput phenotyping of leaf physiological responses to ozone stress using hyperspectral reflectance spectra of diverse maize inbred and hybrid lines. Leaf traits were measured with standard wet-laboratory and gas-exchange approaches alongside measurements of leaf reflectance. Statistical approaches were used to develop measures of leaf biochemical, structural and photosynthetic properties. This approach was dramatically faster than traditional measurements, enabling over 1,000 rows to be phenotyped during midday hours over just 2 to 4 days. This work offers a nondestructive method to accurately assess physiological and biochemical trait responses to environmental stress. 04 Leaf and canopy scale drivers of genotypic variation in soybean response to elevated carbon dioxide concentration. In order to maximize yields under future atmospheric carbon dioxide concentrations, we need to identify and study crop cultivars that respond most favorably to elevated carbon dioxide and understand the mechanisms contributing to their responsiveness. Scientists at ARS and University of Illinois scientists in Urbana, Illinois studied the physiological basis for variation in yield response to elevated carbon dioxide in two cultivars of soybean, Loda and HS93-4118. Seed yield increased by 26% at elevated carbon dioxide concentration in the responsive cultivar Loda, but only by 11% in HS93-4118. Radiation use efficiency and harvest index were key traits underpinning differences in cultivar response. This research provides conceptual basis for modeling genotypic variation in soybean response to elevated carbon dioxide and identifies traits that could be used to select genotypes better adapted to future atmospheric conditions. 05 Increasing drought will diminish the benefits of elevated carbon dioxide for soybean yields across the US Midwest. Understanding the interaction of rising atmospheric carbon dioxide concentrations and water stress is important to future predictions of crop productivity and food security. Researchers from ARS Urbana, Illinois, Stanford University, and the University of Illinois used a crop model to investigate the interaction of rising atmospheric carbon dioxide concentration and drought stress, using data from a long-term field experiment to parameterize and validate the model. We found that the yield response of soybean to elevated carbon dioxide concentration declined with increasing drought stress, opposite to previous expectation. As model projections show increased frequency of drought in the future, the results suggest that the benefits of elevated carbon dioxide concentration on soybean yield will be limited over the U.S. Midwest. 06 Regulatory role of Rubisco activase phosphorylation. Rubisco is the CO2-fixing enzyme of the Calvin-Benson Cycle upon which all plant and crop productivity is dependent and Rubisco activity requires the continual �molecular chiropractic activity� of its helper protein, activase. Rubisco activase is known to be controlled by redox regulation (reversible oxidation/reduction of two cysteine residues) such that its activity fluctuates with changes in light intensity and as a result Rubisco activity changes accordingly. Recent results indicate that the activase protein is phosphorylated when leaves are darkened and thus may contribute to control of activase activity and in turn Rubisco activity. Preventing the phosphorylation of activase strongly inhibited plant growth. 07 Autophosphorylation on Serine-318 primes CPK28 for Ca2+ -activation. Calcium (Ca2+)-dependent protein kinases (CPKs) are integral components of signaling pathways downstream of myriad internal and external stimuli. CPKs are composed of a protein kinase domain tethered to a Ca2+sensor region through which the majority of CPKs are directly activated by Ca2+-binding. The CPKs are known to autophosphorylate extensively, but whether autophosphorylation plays a regulatory role is unknown. To address this question, we developed a novel approach for producing recombinant Arabidopsis thaliana CPK28, which plays an important role in regulating plant immune homeostasis, with different levels of autophosphorylation. Autophosphorylated CPK28 was active at lower free Ca2+ (~0.5 �M), and had enhanced activity at higher free Ca2+ (~1 �M), compared to the dephosphorylated protein. Mass spectrometry and site-directed mutagenesis studies identified Ser-318 as the essential autophosphorylation site for Ca2+-sensitivity priming. Immunological analysis with site- and phosphorylation-specific antibodies showed that CPK28 could autophosphorylate on Ser-318 at low free Ca2+ (0.1 �M; considered to be the �resting� level), suggesting that Ser-318 autophosphorylation might fulfill a self-priming function. Taken together, our analyses identify a specific autophosphorylation site controlling Ca2+-activation of CPK28, and lend biochemical support to the Ca2+-sensitivity priming hypothesis for Ca2+-signaling specificity. 08 New chloroplast glycolate transporter involved in photorespiration. ARS scientists in Urbana, Illinois showed that the protein BASS6 is located in the chloroplast envelope membrane and functions in parallel with a previously identified transporter to export the photorespiratory metabolite glycolate out of chloroplast into the photorespiratory pathway. This discovery informs our understanding of the pathway of photorespiratory flux and identifies a genetic target for enhancing the activity of more efficient synthetic photorespiratory pathways that we have installed in chloroplasts. Thus by inactivating this transporter more of the glycolate flux can be forced through the more efficient synthetic pathway and away from the energetically costly native pathway. 09 Dramatically reducing leaf chlorophyll improved light and nitrogen use efficiency in soybean. ARS scientists in Urbana, Illinois demonstrated that soybean plants over invest in the amount of chlorophyll contained in soybean leaves. Reducing chlorophyll by more than 50% resulted in a substantial increase in both light and nitrogen use efficiency. Reducing chlorophyll was predicted by modeling improve light energy use efficiency by improving light energy distribution in the canopy. 10 Sink demand is essential to sustain the stimulation of photosynthesis by elevated CO2. ARS scientists in Urbana, Illinois collaborating with University of Illinois scientists conducted a field study using FACE (Free Air Concentration Enrichment) technology to demonstrate maintaining a strong sink for photosynthetic products is required to sustain the stimulation of photosynthesis and prevent down regulation of photosynthetic genes. This experiment was the first field validation of the role of sink strength in preventing the down regulation of photosynthesis that frequently occurs when crop plants are grown at elevated CO2.
Impacts
(N/A)
Publications
- Xia, P., Zhang, G., Walker, B.J., Seo, S., Kwak, S., Liu, J., Kim, H., Ort, D.R., Wang, S., Jin, Y. 2016. Recycling carbon dioxide during xylose fermentation by engineered Saccharomyces cerevisiae. ACS Synthetic Biology. 6(2):276-283.
- Niinemets, U., Berry, J.A., von Caemmerer, S., Ort, D.R., Parry, M., Poorter, H. 2017. Photosynthesis: ancient, essential, complex, diverse ... and in need of improvement in a changing world. New Phytologist. 213:43-47.
- Walker, B.J., Orr, D.J., Carmo-Silva, E., Parry, M., Bernacchi, C.J., Ort, D.R. 2017. Uncertainty in measurements of the photorespiratory CO2 compensation point and its impact on models of leaf photosynthesis. Photosynthesis Research. 132(3):245-255.
- Siebers, M.H., Slattery, R.A., Yendrek, C.R., Locke, A.M., Drag, D., Ainsworth, E.A., Bernacchi, C.J., Ort, D.R. 2017. Simulated heat waves during maize reproductive stages alter reproductive growth but have no lasting effect when applied during vegetative stages. Agriculture, Ecosystems and Environment. 240:162-170.
- Koehler, I.H., Ruiz-Vera, U.M., VanLoocke, A., Thomey, M.L., Clemente, T., Long, S.P., Bernacchi, C.J., Ort, D.R. 2016. Expression of cyanobacterial FBP/SBPase in soybean prevents yield depression under future climate conditions. Journal of Experimental Botany. 68(3):715-726.
- Slattery, R.A., VanLoocke, A., Bernacchi, C.J., Zhu, X., Ort, D.R. 2017. Photosynthesis, light use efficiency, and yield of reduced-chlorophyll soybean mutants in field conditions. Frontiers in Plant Physiology. doi. org/10.3389/fpls.2017.00549.
- Sanz-Saez, A., Koester, R., Rosenthal, D., Montes, C., Ort, D.R., Ainsworth, E.A. 2017. Leaf and canopy scale drivers of genotypic variation in soybean response to elevated carbon dioxide concentration. Global Change Biology. 23(9):3908-3920.
- Soleh, M.A., Tanaka, Y., Kim, S., Huber, S.C., Sakoda, K., Shiraiwa, T. 2017. Identification of large variation in the photosynthetic induction response among 37 soybean genotypes that is not correlated with steady- state photosynthetic capacity. Photosynthesis Research. 131(3):305-315.
- Bender, K.W., Blackburn, R., Monaghan, J., Zipfel, C., Goshe, M.B., Zielinski, R.E., Huber, S.C. 2017. Autophosphorylation-based calcium (Ca2+) sensitivity priming and Ca2+/Calmodulin inhibition of Arabidopsis thaliana Ca2+-dependent protein kinase 28 (CPK28). Journal of Biological Chemistry. 292:3988-4002.
- Ainsworth, E.A. 2017. Understanding and improving global crop response to ozone pollution. Plant Journal. 90(5):886-897.
- Yendrek, C.R., Tomaz, T., Montes, C., Cao, Y., Morse, A.M., Brown, P.J., McIntyre, L.M., Leakey, A., Ainsworth, E.A. 2017. High-throughput phenotyping of maize leaf physiological and biochemical traits using hyperspectral reflectance. Plant Physiology. 173:614-626.
- Wagner, M., Wang, M., Miguez-Macho, G., Miller, J., VanLoocke, A., Bagley, J., Bernacchi, C.J., Georgescu, M. 2017. A realistic meteorological assessment of perennial biofuel crop deployment: a southern Great Plains perspective. Global Change Biology Bioenergy. 9(6):1024-1041.
- Wang, M., Wagner, M., Miguez-Macho, G., Kamarianakis, Y., Mahalov, A., Moustaoui, M., Miller, J., VanLoocke, A., Bagley, J.E., Bernacchi, C.J., Georgescu, M. 2017. On the long-term hydroclimatic sustainability of perennial bioenergy crop expansion over the United States. Journal of Climate. 30:2535-2557.
- South, P.F., Walker, B.J., Cavanagh, A.P., Badger, M., Ort, D.R. 2017. Bile acid sodium symporter BASS6 can transport glycolate and is involved in photorespiratory metabolism in Arabidopsis thaliana. The Plant Cell. doi:10.1105/tpc.16.00775.
- Gray, S.B., Demody, O., Klein, S.P., Locke, A.M., McGrath, J.M., Paul, R.E. , Rosenthal, D.M., Ruiz-Vera, U.M., Seibers, M.H., Strellner, R., Ainsworth, E.A., Bernacchi, C.J., Ort, D.R. 2016. Intensifying drought eliminates the expected benefits of elevated [CO2] for soybean. Nature Plants. 2:16132.
- Slattery, R.A., Grennan, A.K., Sivaguru, M., Sozzani, R., Ort, D.R. 2016. Light sheet microscopy reveals more gradual light attenuation in light green versus dark green soybean leaves. Journal of Experimental Biology. 67:4697-4709.
- Joo, E., Hussain, M., Zeri, M., Masters, M., Miller, J.N., Gomez-Casanovas, N., DeLucia, E., Bernacchi, C.J. 2016. The influence of drought-heat stress on long term carbon fluxes of bioenergy crops grown in the Midwestern US. Plant Cell and Environment. 39:1928-1940.
- Zhu, P., Zhuang, Q., Joo, E., Bernacchi, C.J. 2017. Importance of biophysical effects on climate warming mitigation potential of biofuel crops over the conterminous United States. Global Change Biology Bioenergy. 9:577-590.
- Nelson, A.J., Koloutsou-Vakakis, S., Rood, M., Myles, L., Lehmann, C., Bernacchi, C.J., Balasubramanian, S., Joo, E., Heuer, M., Vieira-Filho, M. 2017. Ammonia flux above fertilized corn in central Illinois, USA, using relaxed eddy accumulation. Agricultural and Forest Meteorology. 239:202- 212.
- Balasubramanian, S., Nelson, A.J., Koloutsou-Vakakis, S., Lin, J., Rood, M. J., Myles, L., Bernacchi, C.J. 2017. Evaluation of DeNitrification DeComposition model for estimating ammonia fluxes from chemical fertilizer application. Agricultural and Forest Meteorology. 237:123-34.
- Singh, V., Perraki, A., Kim, S., Shrivastava, S., Lee, J., Zhao, Y., Schwessinger, B., Marshall-Colon, A., Zipfel, C., Huber, S.C. 2017. Tyrosine-610 in the receptor kinase BAK1 does not play a major role in brassinosteroid signaling or innate immunity. Frontiers in Plant Physiology. doi: 10.3389/fpls.2017.01273.
- Moffett, A.S., Bender, K.W., Huber, S.C., Shukla, D. 2017. Molecular dynamics simulations reveal the conformational dynamics of Arabidopsis thaliana BRI1 and BAK1 receptor-like kinases. Journal of Biological Chemistry. doi: 10.1074/jbc.M117.792762.
- Walker, B.J., South, P.F., Ort, D.R. 2016. Photorespiration maintains carbon recycling efficiency at low irradiance despite impaired glycolate/ glycerate antiport or hydroxypyruvate reduction. Plant Physiology. 129(1) :93-103.
- Siebers, M.H., Slattery, R.A., Yendrek, C.R., Locke, A.M., Drag, D., Ainsworth, E.A., Bernacchi, C.J., Ort, D.R. 2017. Heat waves alter reproductive growth in maize without long-term effects on photosynthesis and plant water status. Agriculture Ecosystems and the Environment. 240:162-170.
- Locke, A.M., Ort, D.R. 2015. Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] reveals anisohydric water management in field-grown soybean. Environmental and Experimental Botany. 116:39-46.
- Ruiz-Vera, U.M., De Souza, A.P., Long, S.P., Ort, D.R. 2017. The role of sink strength and nitrogen availability in the down-regulation of photosynthetic capacity in field-grown Nicotiana tabacum at elevated CO2 concentration. Frontiers in Plant Science. doi.org/10.3389/fpls.2017.00998.
|
Progress 10/01/15 to 09/30/16
Outputs
Progress Report Objectives (from AD-416): Objective 1: Engineer improved photosynthetic efficiency in food, feed, and biofuel crops for improved yields. 1.1 Determine the optimal chlorophyll (Chl) content to maximize the daily integral of canopy photosynthesis. 1.2 Decrease photorespiration by improving the effectiveness of engineered chloroplast photorespiratory bypass pathways by lowering the activity of the chloroplast glycolate exporter. Objective 2: Define the key posttranslational regulatory factors controlling assimilation/partitioning and growth in crop plants. 2.1 Investigate historical and diverse soybean germplasm to study fundamental interactions and constraints between carbon and nitrogen metabolism, and their influence on soybean yield and seed quality. 2.2 Characterize the brassinosteroid (BR) receptor kinase, BRI1, and identify phosphosites that can be manipulated by directed mutagenesis to alter kinase activity or specificity. 2.3 Identify protein interactors with key receptor kinases with specific attention to those where the interaction is phosphorylation dependent and/ or plays a regulatory role. Objective 3: Determine the major features, physiological and genetic, and the mechanistic basis for the response of crops to elevated atmospheric CO2 and tropospheric ozone, and determine their interactions with temperature and drought. 3.1 Investigate the response of growth, photosynthesis and carbohydrate metabolism to elevated CO2 in species with different phloem loading strategies. 3.2 Use functional genomic and quantitative genetic approaches to dissect the genetic basis for ozone tolerance in crops. 3.3 Investigate and compare the physiological and agronomic responses of maize and soybean to heat waves. Objective 4: Determine the linkages between whole plant, physiological and genetic, and ecosystem processes to maximize key ecosystem services for current and alternative bioenergy production systems in the context of carbon, water, and nutrient cycling and energy partitioning. 4.1 Investigate the benefits associated with improving photosynthetic efficiency and/or light attenuation through crop canopies that extend beyond higher productivity. 4.2 Model the regional impacts of improved carbon uptake, carbon sequestration in soils, greenhouse gas emissions, and canopy water use on local- and regional-scale biogeochemical cycles using coupled biosphere- atmosphere-hydrology models. 4.3 Investigate through field measurements and mechanistic ecosystem models the impact of land-use change to accommodate bioenergy feedstock species on regional productivity and ecosystem services. Approach (from AD-416): The overall goal of this research is to identify molecular, biochemical, and genetic determinants of photosynthate production and distribution in crop plants and to utilize this new information to address specific agricultural problems of national importance including those associated with atmospheric change. The experimental approaches are diverse combining biophysics, biochemistry, physiology, molecular biology, and genomics with both laboratory and field components. The approaches used to meet the goals of Objective 1 for improving photosynthetic efficiency of crop plants will center on developing a canopy light energy distribution and two separate strategies to lower soybean leaf chlorophyll. Objective 2 that seeks to key regulatory steps controlling assimilation, partitioning and growth will be approached using a "common garden" experiment with historical soybean cultivars, site directed mutagensis of phytohormone receptors and yeast two-hybrid procedures to find interacting partners of the receptors. Objective 3 involves determining factors controlling the response of crops to global change factors will use Free Air Concentration Enrichment technology (FACE) to impose interacting treatments in a replicated factorial experimental design under field conditions. Objective 4 is intended to discover linkages that scale from leaves to ecosystem responses where the approach relies centrally on large scale flux measurements by eddy covariance technologies. Work is underway to identify the regulatory mechanisms controlling Rubisco activase and to develop transgenic plants lacking these mechanisms to determine whether plant growth can be improved in the field environment, where light intensity can fluctuate rapidly. Ecosystem modeling work has been conducted to improve model predictive ability for a wide range of species over a wide range of present and future conditions. Specifically, conventional and no-till components of an ecosystem model have been evaluated against existing measured data for a large number of years for maize and soybean. Climate model outputs have been incorporated into ecosystem models to assess ecosystem functioning over a wide range of current and future environmental conditions. Ecosystem models have been linked with hydrology models to determine how ecosystem functioning can influence water quantity and quality for the Midwestern US. Field-based measurements have been expanded to include a diverse number of ecosystems throughout key agricultural regions of the U.S., including the Midwestern US agricultural ecosystems and subtropical grazed pastures in the South-Eastern U.S. Coupled with these intensive field campaigns are sampling campaigns to provide the ancillary data needed to parameterize mechanistic models to scale measurements from the field to the region. Accomplishments 01 Plasticity revealed in chloroplast envelope photorespiratory transporters. ARS scientists in Urbana, Illinois, showed that the recycling of photorespiratory two carbon and three carbon intermediates is not perfectly efficient further increasing the loss in photosynthetic efficiency due to photorespiration. The purpose of this study is to investigate the plasticity of glycolate/glycerate transport during photorespiration through measurements of gas exchange of glycolate transporter mutants under photorespiratory and non- photorespiratory conditions. The findings show that the biochemistry of photorespiration can change with environmental conditions possibly revealing a previously unknown phototprotective mechanism. 02 Light sheet microscopy reveals more gradual light attenuation in light- green versus dark-green soybean leaves. ARS scientists, Urbana, Illinois, in collaboration with academic collaborators, using the new technology of light sheer microscopy have quantified the changes in light transmission through soybean of differing chlorophyll content. Reducing chlorophyll was expected to reduce the disparity of light availability between the upper and lower chloroplasts of the leaf, reduce the modeled gradient of photosynthesis across the leaf, and therefore explain the increases in light-green soybean mutant photosynthetic efficiency at the leaf level. It was shown that greater light absorption occurred in deeper leaf layers of the light-green mutant leaf with the most noticeable differences in blue light. In addition, modeled leaf photosynthetic profiles based on chlorophyll profiles and Beer�s Law were also more gradual in the mutants. Thus these data strongly support the idea that reducing pigment concentration in crop leaves results in improved light use efficiency. 03 Redesigning photosynthesis to sustainably meet global food and bioenergy demand. ARS scientist in Urbana, Illinois led a group of 24 international photosynthesis experts to develop a road map for improving agricultural production by improving photosynthetic efficiency. An array of prospective redesigns of plant systems at various scales were developed, all aimed at increasing crop yields through improved photosynthetic efficiency and performance. Prospects range from straightforward alterations, already supported by preliminary evidence of feasibility, to substantial redesigns that are currently only conceptual, but that may be enabled by new developments in synthetic biology. Although some proposed redesigns are certain to face obstacles that will require alternate routes, the efforts should lead to new discoveries and technical advances with important impacts on the global problem of crop productivity and bioenergy production. 04 New post-translational modification of Rubisco activase. Rubisco is the CO2-fixing enzyme of the Calvin-Benson Cycle upon which all plant and crop productivity is dependent and Rubisco activity requires the continual �molecular chiropractic activity� of its helper protein, activase. Rubisco activase is known to be controlled by redox regulation (reversible oxidation/reduction of two cysteine residues) such that its activity fluctuates with changes in light and as a result Rubisco activity changes accordingly. Recent results from our laboratory indicate that activase is phosphorylated on a specific residue (threonine-78) when leaves are darkened and thus phosphorylation emerges as a new biochemical mechanism that may contribute to control of activase activity. Emerging evidence suggests that phosphorylation of Thr78 acts in concert with redox regulation of activase to control Rubisco activity. Identifying post-translational modifications provides an opportunity to manipulate pathways using genome editing technologies and thus have impact on both science and technology. 05 Ca2+ signaling just got more complex. Numerous signaling pathways in plants are coordinated by controlled release of calcium (Ca2+) into the cytosol from external or internal stores. These changes in cytosolic Ca2+ are perceived by a suite of Ca2+ sensor proteins (e.g., Calmodulin, CaM) or responder proteins (e.g., Ca2+ dependent protein kinases, CPKs) . Both types of proteins directly bind Ca2+, which impacts their function in some way. Surprisingly, results from ARS in Urbana, Illinois document that the sensor protein calmodulin binds with high affinity to a responder protein, CPK28. Binding of CaM6 to CPK28 in vitro inhibited autophosphorylation of CPK28 and thus has potential functional impact. These results have identified a new player in plant Ca2+ signaling in plants that is an important step toward a full mechanistic understanding of the centrally important but high complex process involved in plant responses to environmental conditions. 06 Photosynthetic capacity has not improved with breeding for increased yields in historical soybean varieties. ARS and University of Illinois, Urbana, Illinois researchers investigated how photosynthesis and respiration have changed with breeding in 24 soybean cultivars released from 1923 to 2007. Results showed that maximum photosynthetic capacity and nighttime respiration rates have not changed with cultivar release date. However, daily carbon gain was significantly greater in more recently released cultivars when stomatal conductance was high. Previous work has shown that modern soybean cultivars yield more than old cultivars in all environments, but gains are greater in high- yielding environments. This study provides a physiological explanation for that observation in that under conditions of ample soil moisture, stomatal conductance was greater in modern cultivars, supporting greater daily C gain. 07 The sensitivity to ozone in soybean cultivars has increased over time. ARS scientists in Urbana, Illinois and international collaborators used ozone-exposure data for 49 soybean cultivars from 28 experimental studies to produce updated ozone-dose response functions for soybean. Ozone sensitivity of soybean cultivars increased by an average of 32.5% between 1960 and 2000, suggesting that selective breeding strategies targeting high yield and high stomatal conductance may have inadvertently selected for greater ozone sensitivity over time. Genotypes from China and India showed greater ozone sensitivity than genotypes from the U.S. This analysis suggests that local climatic factors and particular physiological traits in different regions may alter ozone sensitivity of soybean, a stress that currently reduces global soybean yields by ~10%. 08 Canopy photosynthesis is decreased by elevated ozone. ARS scientists in Urbana, Illinois and international partners examined the effects of elevated ozone on vertical changes in leaf area, light interception, and leaf physiology to provide a mechanistic explanation of the effect of ozone on canopy photosynthesis. Leaf area decreased with increasing ozone, allowing greater light penetration to the canopy. However, there were reductions in photosynthesis and increases in respiration with rising ozone concentrations. Sensitivity analysis showed that changes in leaf physiology, not leaf area, resulted in lower canopy photosynthesis. 09 Intensifying drought eliminates the expected benefits of elevated [CO2] for soybean. ARS, Urbana, Illinois and collaborators investigated the interaction of drought stress and elevated [CO2] on soybean productivity. Although it was expected that elevated [CO2] would benefit soybean to a greater extent with increasing drought stress, this was not observed in the long-term study. Elevated [CO2] resulted in lower stomatal conductance and greater soil moisture in some years, but in years with greater drought stress, plants grown at elevated [CO2] had greater sensitivity to soil drying, impaired nitrogen fixation and less soil moisture available. Thus, as drought stress increased in intensity, the beneficial effects of elevated [CO2] were diminished. Hotter and dryer growing conditions are forecast for the future, and this study showed that elevated [CO2] will not protect soybean from these detrimental conditions. 10 Assessing the potential to decrease the Gulf of Mexico hypoxic zone with Midwest U.S. perennial cellulosic feedstock production. Nutrient additions to agricultural ecosystems leads to a large hypoxic zone in the Gulf of Mexico. Transition to perennial ecosystem for bioenergy production can lead to ecosystems that are more efficient in removing nutrients from soil and water and require less nutrient overall. Measurements of perennial ecosystems ability to take nutrients from the soil were scaled under a range of scenarios to assess the impacts on quantity and quality of water flowing from the Mississippi River into the Gulf of Mexico and the results show that more perennial grasses established throughout the Midwestern U.S. leads to small changes in water quantity but substantial improvements in water quality. 11 The influence of drought-heat stress on long-term carbon fluxes of bioenergy crops grown in the Midwestern U.S. Perennial feedstocks are ideally suited for next generation bioenergy production but little is known of their response to climate extremes. ARS researchers in Urbana, Illinois measured long-term carbon exchange between three perennial bioenergy feedstocks and compared the results to a traditional maize/ soybean ecosystem. The long-term measurements encompassed a significant drought. The results show that all perennial ecosystems are more resilient to drought than maize/soybean, although the extent of resilience was not consistent among all perennial ecosystems. 12 Refining greenhouse gas emission estimates from grasslands. Greenhouse gases, including carbon dioxide, methane, and nitrous oxide, are primarily responsible for increasing global temperatures. Grasslands play an important role in determining the concentration of greenhouse gases in the atmosphere. Changes in the rate of nitrogen, a fertilizer, addition to grasslands can influence the emissions of greenhouse gases. Many experiments have been conducted to determine the relationship between nitrogen deposition and greenhouse gas emissions, and ARS scientists in Urbana, Illinois compiled a large number of these studies and general patterns in nutrient treatments were determined. The vast majority of nitrogen additions were higher than levels these ecosystems will experience in the future, and represented extreme, unlikely treatments. This means that the experimental treatments were too high, even for future conditions. The results of this work will both help to guide the selection of optimum nitrogen addition rates, and identify upper and lower boundaries on estimates of future greenhouse gas emissions from grasslands. 13 Elevated CO2 and temperature increase soil C losses from a soy-maize ecosystem. Soils respire carbon dioxide through microbial activity that breaks down organic matter. As soils get warmer, they respire more. However, there is very little predictive ability for rates of soil respiration as ecosystems warm. ARS scientists in Urbana, Illinois artificially warmed soils over three years using infrared heating technology. Respiration rates were measured routinely and used to develop an ecosystem model to simulate the effects of warming and rising atmospheric CO2 on soil respiration rates. The results show that the microbes released 10% more CO2 from increased activity in the warmer temperatures and higher CO2. The respiration from plant roots decreased by 25% in the heated plots. Because the microbes are consuming stored carbon, the increase in soil respiration in the heating will likely lead to losses of soil carbon and the rising in CO2 will not likely offset this effect.
Impacts
(N/A)
Publications
- Miller, J.N., VanLoocke, A., Gomez-Casanovas, N., Bernacchi, C.J. 2015. Candidate perennial bioenergy grasses have a higher albedo than annual row crops in the Midwestern US. Global Change Biology Bioenergy. 21:4237-4249.
- Mitra, S.K., Chen, R., Dhundaydham, M., Wang, X., Blackburn, R.K., Kota, U. , Goshe, M.B., Schwartz, D., Huber, S.C., Clouse, S.D. 2015. An autophosphorylation site database for leucine-rich repeat receptor-like kinases in Arabidopsis thaliana. Plant Journal. 82(6):1042-1060.
- Ort, D.R., Merchant, S.S., Alric, J., Barkan, A., Blankenship, R.E., Bock, R., Croce, R., Hanson, M.R., Long, S.P., Moore, T.A., et al. 2015. Redesigning photosynthesis to sustainably meet global food and bioenergy demand. Proceedings of the National Academy of Sciences. 112(28):8529-8536.
- Gomez-Casanovas, N., Hudiburg, T., Bernacchi, C.J., Parton, W., DeLucia, E. 2016. Nitrogen deposition and greenhouse gas emissions from grasslands: uncertainties and future directions. Global Change Biology. 22:1348-1360.
- Bernacchi, C.J., VanLoocke, A. 2015. Terrestrial ecosystems in a changing environment. Annual Reviews of Plant Biology. 66:599-622.
- Walker, B.J., Skabelund, D.C., Busch, F., Ort, D.R. 2016. An improved approach for measuring the impact of multiple CO2 conductances on the apparent photorespiratory CO2 compensation point through slope-intercept regression. Plant Cell and Environment. 39:1109-1203.
- Ruiz-Vera, U.M., Siebers, M.H., Drag, D.W., Ort, D.R., Bernacchi, C.J. 2015. Canopy warming caused photosynthetic acclimation and reduced seed yield in maize grown at ambient and elevated [CO2]. Global Change Biology. 21:4237-4249.
- Betti, M., Bauwe, H., Bush, F., Fernie, A.R., Keech, O., Levey, M., Ort, D. R., Parry, M., Sage, R., Timm, S., Walker, B.J., Weber, A. 2016. Manipulating photorespiration to increase plant productivity. Recent advances and perspectives for crop improvement. Journal of Experimental Botany. 67(10):2977-2988.
- Kim, S., Bender, K.W., Walker, B.J., Salvucci, M.E., Zielinski, M.E., Spalding, M.H., Ort, D.R., Huber, S.C. 2016. The plastid casein kinase 2 phosphorylates Rubisco activase at the Thr-78 site but is not essential for regulation of Rubisco activation state. Frontiers in Plant Science. doi: 10.3389/fpls.2016.00404.
- Walker, B.J., South, P.F., Ort, D.R. 2016. Physiological evidence for plasticity in glycolate/glycerate transport during photorespiration. Photosynthesis Research. 129:93-103.
- Locke, A.M., Ort, D.R. 2015. Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] and reveals anisohydric water management in field-grown soybean. Environmental and Experimental Botany. 116:39-46.
- Osborne, S.A., Mills, G., Hayes, F., Ainsworth, E.A., Buker, P., Emberson, L. 2016. Has the sensitivity of soybean cultivars to ozone pollution increased with time? An analysis of published dose-response data. Global Change Biology. doi: 10.1111/gcb.13318.
- Ainsworth, E.A. 2016. The importance of intraspecific variation in tree responses to elevated [CO2]: breeding and management of future forests. Tree Physiology. 36:679-681.
- Oikawa, S., Ainsworth, E.A. 2016. Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient. Environmental Pollution. 215:347-355.
- Koester, R.P., Nohl, B.M., Diers, B.W., Ainsworth, E.A. 2016. Has photosynthetic capacity increased with 80 years of soybean breeding? An examination of historical soybean cultivars. Plant Cell and Environment. 39:1058-1067.
- McGrath, J.M., Betzelberger, A.M., Wang, S., Shook, E., Zhu, X., Long, S.P. , Ainsworth, E.A. 2015. The grain drain. Ozone effects on historical maize and soybean yields. Proceedings of the National Academy of Sciences. 112:14390-14395.
- Chamberlain, S.D., Gomez-Casanovas, N., Walter, M., Boughton, E., Bernacchi, C.J., DeLucia, E., Groffman, P.M., Keel, E.W., Sparks, J.P. 2016. Influence of transient flooding on methane fluxes from subtropical pastures. Journal of Geophysical Research-Biogeosciences. 121:965-977.
- Black, C.K., Davis, S.C., Hudiburg, T.W., Bernacchi, C.J., DeLucia, E.H. 2016. Elevated CO2 and temperature increase soil C losses from a soy-maize ecosystem. Global Change Biology. doi:10.111/gcb.13378.
- VanLoocke, A., Twine, T., Kucharik, C., Bernacchi, C.J. 2016. Assessing the potential to decrease the Gulf of Mexico hypoxic zone with Midwest US perennial cellulosic feedstock production. Global Change Biology Bioenergy. doi:10.1111/gcbb/12385.
- Huber, S.C., Li, K., Nelson, R.L., Ulanov, A., Demuro, C., Baxter, I.R. 2016. Canopy position has a profound effect on soybean seed composition. PeerJ. 4:e2452.
|
Progress 10/01/14 to 09/30/15
Outputs
Progress Report Objectives (from AD-416): Objective 1: Engineer improved photosynthetic efficiency in food, feed, and biofuel crops for improved yields. 1.1 Determine the optimal chlorophyll (Chl) content to maximize the daily integral of canopy photosynthesis. 1.2 Decrease photorespiration by improving the effectiveness of engineered chloroplast photorespiratory bypass pathways by lowering the activity of the chloroplast glycolate exporter. Objective 2: Define the key posttranslational regulatory factors controlling assimilation/partitioning and growth in crop plants. 2.1 Investigate historical and diverse soybean germplasm to study fundamental interactions and constraints between carbon and nitrogen metabolism, and their influence on soybean yield and seed quality. 2.2 Characterize the brassinosteroid (BR) receptor kinase, BRI1, and identify phosphosites that can be manipulated by directed mutagenesis to alter kinase activity or specificity. 2.3 Identify protein interactors with key receptor kinases with specific attention to those where the interaction is phosphorylation dependent and/ or plays a regulatory role. Objective 3: Determine the major features, physiological and genetic, and the mechanistic basis for the response of crops to elevated atmospheric CO2 and tropospheric ozone, and determine their interactions with temperature and drought. 3.1 Investigate the response of growth, photosynthesis and carbohydrate metabolism to elevated CO2 in species with different phloem loading strategies. 3.2 Use functional genomic and quantitative genetic approaches to dissect the genetic basis for ozone tolerance in crops. 3.3 Investigate and compare the physiological and agronomic responses of maize and soybean to heat waves. Objective 4: Determine the linkages between whole plant, physiological and genetic, and ecosystem processes to maximize key ecosystem services for current and alternative bioenergy production systems in the context of carbon, water, and nutrient cycling and energy partitioning. 4.1 Investigate the benefits associated with improving photosynthetic efficiency and/or light attenuation through crop canopies that extend beyond higher productivity. 4.2 Model the regional impacts of improved carbon uptake, carbon sequestration in soils, greenhouse gas emissions, and canopy water use on local- and regional-scale biogeochemical cycles using coupled biosphere- atmosphere-hydrology models. 4.3 Investigate through field measurements and mechanistic ecosystem models the impact of land-use change to accommodate bioenergy feedstock species on regional productivity and ecosystem services. Approach (from AD-416): The overall goal of this research is to identify molecular, biochemical, and genetic determinants of photosynthate production and distribution in crop plants and to utilize this new information to address specific agricultural problems of national importance including those associated with atmospheric change. The experimental approaches are diverse combining biophysics, biochemistry, physiology, molecular biology, and genomics with both laboratory and field components. The approaches used to meet the goals of Objective 1 for improving photosynthetic efficiency of crop plants will center on developing a canopy light energy distribution and two separate strategies to lower soybean leaf chlorophyll. Objective 2 that seeks to key regulatory steps controlling assimilation, partitioning and growth will be approached using a "common garden" experiment with historical soybean cultivars, site directed mutagensis of phytohormone receptors and yeast two-hybrid procedures to find interacting partners of the receptors. Objective 3 involves determining factors controlling the response of crops to global change factors will use Free Air Concentration Enrichment technology (FACE) to impose interacting treatments in a replicated factorial experimental design under field conditions. Objective 4 is intended to discover linkages that scale from leaves to ecosystem responses where the approach relies centrally on large scale flux measurements by eddy covariance technologies. Multi-gene constructs have been transformed into tobacco to down regulate chlorophyll biosynthesis as well as to install a synthetic glycolate oxidation pathway to bypass the native photorespiratory pathway. Work is underway to select homozygous T1 lines of these transformants from which T2 plants will be generated for detailed phenotyping. An auxiliary glycolate exporter has been identified that has been conclusively localized to the chloroplast envelope. Experiments are on-going to determine if this exporter cofunctions as a glycerate importer. Work is also in progress to develop transformation protocols for rice in order to expand tobacco proven transformations into an important monocot crop. Soybean bean plants have been transformed with transgenes to increase source leaf sucrose export capacity to investigate the hypothesis that sucrose export is limiting when soybean is grown at elevated carbon dioxide levels. Heat wave experiments are being conducted with soybean to investigate the interaction of heat waves and elevated CO2. Experiments are also underway to examine potential sink limitation in tobacco. Work is underway to develop high through put methods to assess the CO2 compensation point, which will be employed to provide in vitro confirmation of variation in the temperature dependence of Rubisco kinetics across widely dispersed species. This work is intended to identify superior Rubisco enyzmes for eventual introduction into crop plants. Accomplishments 01 Inoculation with an enhanced N2-fixing Bradyrhizobium japonicum strain (USDA110) does not alter soybean (Glycine max Merr.) response to elevated [CO2]. ARS researchers at Urbana, IL and University of Illionis researchers tested the hypothesis that inoculation with a selected rhizobium strain (USDA110) that performs high rates of N2 fixation could improve soybean response to elevated [CO2]. In the field, treatments with USDA110, while increasing infection nearly tenfold, did not result in greater photosynthesis, growth, seed yield or seed N content. Nor did inoculation with USDA110 alter the response of these traits to elevated [CO2]. In a controlled environment study, there was substantial benefit of inoculation with USDA110 in sterile soil on soybean growth and biomass production, meaning there is potential for rhizobia treatment to stimulate soybean yield, but only in soils with little or no history of prior soybean production, and thus not likely to be useful in traditional soybean growing regions. 02 Ozone effects on historical maize and soybean yields. To date, there have been no estimates of the actual field yield losses in the USA from exposure to ozone, an atmospheric pollutant, even though such estimates are valuable for estimating food production and for cost-benefit analyses of reducing ground-level ozone. ARS from Urbana, IL and University of Illinois researchers used regression analyses of historical yield, climate and ozone data for the USA to determine the ozone-induced loss of production for maize and soybean from 1980 to 2008. Analyses showed that over that ~30 year period, production of soybean and maize were reduced by ~5% and ~10%. This work provides further evidence for the damaging effects of ozone on agriculture, and suggests that improved emission controls or the development of tolerant germplasm are needed to overcome these losses. 03 Variation in legume sensitivity to ozone. ARS researchers investigated the response of soybean and two other legumes, pea and common bean, to elevated ozone concentrations. The three species had very different leaf-level responses to ozone, with pea being tolerant and soybean and common bean increasingly sensitive to ozone. Leaf biochemical and transcriptional responses indicated that pea had greater capacity for detoxification, with greater apoplastic ascorbate content, foliar glutathione content, and rates of respiration than soybean and common bean. These responses of pea could be used to develop screens for more tolerant varieties of soybean and common bean, or used in biotechnology applications to improve their response to elevated ozone. 04 Global change impacts on ecosystem water use. Global change is projected to have a significant impact on many aspects on how ecosystems function. A critical component necessary for ecosystems to maintain productivity, a requirement for food security, is the availability of water. ARS researchers in Urbana, Illinois compiled, analyzed, and provided a review of how ecosystems, including agricultural ecosystem respond in their water use to a changing environment. The review indicated that the direct consequence of rising CO2, the key driver of global change, results in decreases in ecosystem water use, the consequences of rising CO2 on atmospheric temperature and humidity will likely have opposite effects. In addition to presenting a state of current knowledge on this topic, the review indicated directions forward to better understand the important dynamics between ecosystem productivity and water availability. 05 Global warming decreases photosynthesis and yields of Midwestern-grown maize. Conventional studies on major crops responses to a changing environment are limited to artificial growth environment experiments or to historical analysis of agricultural output. ARS researchers in Urbana, Illinois investigated the responses of maize to growth in elevated CO2 and increased temperature using field-based equipment to allow for the plants to be grown under typical agronomic conditions while simultaneously modifying their growth environment in a controlled manner. Maize photosynthetic rates decreased when grown in warmer temperatures and this reduced harvestable yields. The sensitivity of maize to warmer temperature did not appear to be influenced by growth in higher CO2. The outcome from this research indicates that the sensitivity of maize to growth in higher temperatures warrant further investigation into whether opportunities to adapt maize for global changes can offset these impacts. 06 Perennial bioenergy grasses can act to offset local warming through increased reflection of solar radiation. Climate smart agriculture is an integrative approach for increased agricultural output while pursuing opportunities to adapt agriculture to, while minimizing and potentially offsetting, climate change. ARS researchers in Urbana, Illinois adapted an ecosystem model to investigate the role of adapting maize to longer growing seasons and of establishing perennial bioenergy crops on Midwestern climate. The modeling work was based on measurements collected by the ARS scientists at the University of Illinois Energy Farm and the modeling was conducted for present and future climate scenarios. The results indicate that both longer maize growing seasons and establishment of perennial grasses can help offset the direct warming impacts of rising CO2. Without direct opportunities to establish these land-use changes on a large scale, these models provide valuable information needed for future agricultural decisions. 07 Meta analysis of crop energy conversion efficiency sets benchmark for improvements. ARS scientists from Urbana, IL used data from a 164 published studies to evaluate the operating photosynthetic efficiency of crop plants in unstressed conditions in the field. The statistical analysis revealed that solar energy conversion efficiency was greatest in biofuel crops, followed by C4 food crops, C3 crops that don't fix nitrogen, and finally C3 crops that do fix nitrogen. Notably in all cases the efficiencies were less than half of that theoretically possible. The modest analysis further revealed that genetic improvements in energy conversion efficiency have to date been most, less than 0.7% per year, revealing the unrealized potential of improving photosynthesis as a promising contributing strategy to increase yield in order to meet projected future agricultural demand. 08 Heat waves imposed during early pod development in soybean cause significant yield loss. ARS scientists in collaboration with a colleague at the University of Illinois at Urbana-Champaign used in field warming experiments of soybean crop canopies to discover that heat waves during early pod fill was the most vulnerable stage of soybean development to heat waves. This study shows that short high- temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave- induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures. 09 Regulation of Rubisco activase activity. Rubisco is the CO2-fixing enzyme of the crop photosynthesis upon which all plant and crop productivity is dependent and Rubisco activity requires the continual 'molecular chiropractic activity' of its helper protein, activase. Rubisco activase is known to be controlled by redox regulation (reversible oxidation/reduction of two cysteine residues) such that its activity fluctuates with changes in light and as a result Rubisco activity changes accordingly. Recent results from ARS scientists at Urbana, IL show that the enzyme is modified by protein phosphorylation when leaves are darkened. This work reveals that protein phosphorylation as a previously unrecognized biochemical mechanism controlling activase activity and thus regulating Rubisco-dependent photosynthesis. Understanding the full suite of processes that regulate Rubisco activity will be essential for engineering improved photosynthetic efficiency.
Impacts
(N/A)
Publications
- Kimball, B.A., White, J.W., Ottman, M.J., Wall, G.W., Bernacchi, C.J., Morgan, J.A. 2015. Predicting canopy temperatures and infrared heater energy requirements for warming field plots. Agronomy Journal. 107:129-141.
- Slattery, R.A., Ort, D.R. 2015. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops. Plant Physiology. 168:383-392.
- Toomey, M., Friedl, M., Frolking, S., Hufkens, K., Klosterman, S., Sonnentag, O., Baldocchi, D.D., Bernacchi, C.J., Brzostek, E., Burns, S.P. et al. 2015. Greenness indices from digital cameras predict the timing and seasonal dynamics of canopy-scale photosynthesis. Ecological Applications. 25(1):99-115.
- Walker, B.J., Ort, D.R. 2015. Improved method for measuring the apparent CO2 photocompensation point resolves the impact of multiple internal conductances to CO2 to net gas exchange. Plant Cell and Environment. DOI: 10.1111/pce.12562.
- Siebers, M.H., Yendrek, C.R., Drag, D., Locke, A.M., Rios Acosta, L., Leakey, A., Ainsworth, E.A., Bernacchi, C.J., Ort, D.R. 2015. Heat waves imposed during early pod development in soybean (Glycine max) cause significant yield loss despite a rapid recovery from oxidative stress. Global Change Biology. 8(21):3114-3125.
- Leisner, C.P., Ming, R., Ainsworth, E.A. 2014. Distinct transcriptional profiles of ozone stress in soybean (Glycine max) flowers and pods. Biomed Central (BMC) Plant Biology. 14:335.
- Bishop, K.A., Long, S.P., Betzelberger, A.M., Ainsworth, E.A. 2014. Is there the potential to adapt soybean (Glycine max Merr.) to future [CO2]? An analysis of the yield response of 18 genotypes in free air CO2 enrichment. Plant Cell and Environment. 38(9):1765-1774. doi: 10.1111/pce. 12443.
- Sanz-Saez, A., Heath, K.D., Burke, P.V., Ainsworth, E.A. 2015. Inoculation with an enhanced N2-fixing Bradyrhizobium japonicum strain (USDA110) does not alter soybean (Glycine max Merr.) response to elevated [CO2]. Plant Cell and Environment. DOI: 10.1111/pce.12577.
- Yendrek, C.R., Koester, R.P., Ainsworth, E.A. 2015. A comparative analysis of transcriptomic, biochemical and physiological responses to elevated ozone identifies species-specific mechanisms of resilience in legume crops. Journal of Experimental Botany. doi:10.1093/jxb/erv404.
- Campbell, B.W., Mani, D., Curtin, S.J., Slattery, R.A., Michno, J., Ort, D. R., Schaus, P.J., Palmer, R.G., Orf, J.H., Stupar, R.M. 2015. Identical substitutions in magnesium chelatase paralogs result in chlorophyll deficient soybean mutants. Genes, Genomes, Genetics. 5(1):123-131.
- Wang, X., Ort, D.R., Yuan, J. 2015. Photosynthetic terpene hydrocarbon production for fuels and chemicals. Plant Biotechnology Journal. 13(2):137- 146.
- Bagley, J.E., Rosenthal, D.M., Ruiz-Vera, U.M., Siebers, M., Kumar, P., Ort, D.R., Bernacchi, C.J. 2015. The influence of photosynthetic acclimation to rising CO2 and warmer temperatures on leaf and canopy photosynthesis models. Global Biogeochemical Cycles. 29:194-206.
- Bagley, J.E., Miller, J.N., Bernacchi, C.J. 2015. Biophysical impacts of climate-smart agriculture in the Midwest United States. Plant, Cell & Environment. doi: 10.111/pce.12485.
- Woo, D., Quijano, J., Kumar, P., Choaka, S., Bernacchi, C.J. 0214. Threshold dynamics in soil carbon storage for bioenergy crops. Environmental Science and Technology. 48(20):12090-12098.
- Bagley, J.E., Davis, S.C., Georgescu, M., Hussain, M., Miller, J.N., Nesbitt, S.W., VanLoocke, A., Bernacchi, C.J. 2014. The biophysical link between climate, water, and vegetation in bioenergy agro-ecosystems. Biomass and Bioenergy. 71:187-201.
|
Progress 10/01/13 to 09/30/14
Outputs
Progress Report Objectives (from AD-416): Objective 1: Engineer improved photosynthetic efficiency in food, feed, and biofuel crops for improved yields. 1.1 Determine the optimal chlorophyll (Chl) content to maximize the daily integral of canopy photosynthesis. 1.2 Decrease photorespiration by improving the effectiveness of engineered chloroplast photorespiratory bypass pathways by lowering the activity of the chloroplast glycolate exporter. Objective 2: Define the key posttranslational regulatory factors controlling assimilation/partitioning and growth in crop plants. 2.1 Investigate historical and diverse soybean germplasm to study fundamental interactions and constraints between carbon and nitrogen metabolism, and their influence on soybean yield and seed quality. 2.2 Characterize the brassinosteroid (BR) receptor kinase, BRI1, and identify phosphosites that can be manipulated by directed mutagenesis to alter kinase activity or specificity. 2.3 Identify protein interactors with key receptor kinases with specific attention to those where the interaction is phosphorylation dependent and/ or plays a regulatory role. Objective 3: Determine the major features, physiological and genetic, and the mechanistic basis for the response of crops to elevated atmospheric CO2 and tropospheric ozone, and determine their interactions with temperature and drought. 3.1 Investigate the response of growth, photosynthesis and carbohydrate metabolism to elevated CO2 in species with different phloem loading strategies. 3.2 Use functional genomic and quantitative genetic approaches to dissect the genetic basis for ozone tolerance in crops. 3.3 Investigate and compare the physiological and agronomic responses of maize and soybean to heat waves. Objective 4: Determine the linkages between whole plant, physiological and genetic, and ecosystem processes to maximize key ecosystem services for current and alternative bioenergy production systems in the context of carbon, water, and nutrient cycling and energy partitioning. 4.1 Investigate the benefits associated with improving photosynthetic efficiency and/or light attenuation through crop canopies that extend beyond higher productivity. 4.2 Model the regional impacts of improved carbon uptake, carbon sequestration in soils, greenhouse gas emissions, and canopy water use on local- and regional-scale biogeochemical cycles using coupled biosphere- atmosphere-hydrology models. 4.3 Investigate through field measurements and mechanistic ecosystem models the impact of land-use change to accommodate bioenergy feedstock species on regional productivity and ecosystem services. Approach (from AD-416): The overall goal of this research is to identify molecular, biochemical, and genetic determinants of photosynthate production and distribution in crop plants and to utilize this new information to address specific agricultural problems of national importance including those associated with atmospheric change. The experimental approaches are diverse combining biophysics, biochemistry, physiology, molecular biology, and genomics with both laboratory and field components. The approaches used to meet the goals of Objective 1 for improving photosynthetic efficiency of crop plants will center on developing a canopy light energy distribution and two separate strategies to lower soybean leaf chlorophyll. Objective 2 that seeks to key regulatory steps controlling assimilation, partitioning and growth will be approached using a "common garden" experiment with historical soybean cultivars, site directed mutagensis of phytohormone receptors and yeast two-hybrid procedures to find interacting partners of the receptors. Objective 3 involves determining factors controlling the response of crops to global change factors will use Free Air Concentration Enrichment technology (FACE) to impose interacting treatments in a replicated factorial experimental design under field conditions. Objective 4 is intended to discover linkages that scale from leaves to ecosystem responses where the approach relies centrally on large scale flux measurements by eddy covariance technologies. Work is underway to screening tobacco plants with RNAi interference in chlorophyll biosynthesis in tobacco and rice. Experiments are ongoing to select the best of photorespiratory bypass plants for 2015 field testing. Experiments are also on-going to determine the substrate specificity of putative ancillary glycolate export carriers in the chloroplast inner envelope membrane. Experiments are underway to investigation auto and transphosphorylation sites on the phytohormome bassenosteroid receptor protein. Work has started using a yeast two hybrid assay to determine the interaction proteins of BAK1, which itself is an interacting partner of the phytohormome bassenosteroid receptor protein. Soybean bean plants are being transformed to increase source leaf sucrose export capacity to investigate the hypothesis that sucrose export is limiting when soybean is grown at elevated carbon dioxide levels. During the current growing season, samples are being collected in order to perform RNAseq on the most ozone tolerant and ozone sensitive individuals in the soybean recombinant population. The Agro-IBIS model is being expanded to enable the integration of soybean heatwave data. Work is underway to link ecosystem model to the hydrological model in order to assess field-scale responses of the water budget to the altered canopy light environment created by lower leaf chlorophyll content. Significant Activities that Support Special Target Populations: ARS scientists in collaboration with University of Illinois at Champaign- Urbana scientists hosted 26 Jr. High School girls for a week long science camp, Pollen Power. Five girls from under-represented minorities were given fellowships to attend the camp where they learned about microscopy, biology, and current and past climate change. ARS scientist presented a hands-on learning module on "Carbon and Life" for a class of gender and racially diverse 6th grade students at Jefferson Middle School in Champaign, Illinois School District Unit 4. Presented a hands-on learning module focusing on "Measuring Our World" for a class of gender and racially diverse for 3rd grade students at St. Matthew�s Grade School in Champaign, Illinois. Accomplishments 01 Historical gains in soybean (Glycine max Merr.) seed yield are driven by linear increases in light interception, energy conversion, and partitioning efficiencies. ARS scientists in collaboration with colleagues at the University of Illinois at Urbana-Champaign examined 24 soybean genotypes released between 1923 and 2007. Physiological improvements in the efficiencies by which soybean canopies intercepted light, converted light energy into biomass, and partitioned biomass into seed were examined. Seed yield increased by 0.4 bushels/acre/year, and the increase in seed yield was driven by improvements in all three efficiencies. This research showed that light interception efficiency and harvest index are reaching theoretical maximum values in recently released germplasm, but there is still much room to improve photosynthetic efficiency. 02 Distinct transcriptional profiles of ozone stress in soybean (Glycine max) flowers and pods. Elevated ozone caused a decrease in pod formation, but no change in flower production. At the transcriptional level, there was a strong response in both flower and pod tissues, with increased expression of genes involved in signaling in both tissues. Flower tissues also responded to elevated ozone by increasing expression of genes encoding matrix metalloproteinases (MMPs). MMPs are zinc- and calcium-dependent endopeptidases, which cause the hydrolysis of peptide bonds in the middle of polypedtide chains rather than from the ends, have roles in programmed cell death, senescence and stress response in plants. Pod tissues responded to elevated ozone by increasing expression of xyloglucan endotransglucosylase/hydrolase genes, which may be involved with increased pod shattering in elevated ozone. The importance of this study is that it established that gene expression in reproductive tissues of soybean is impacted by elevated ozone, and that diffent reproductive parts (i.e., flowers and pods) have distinct responses. 03 Global analysis of open top chamber and free air CO2 enrichment studies. This study tested current assumptions about the relationships between relative responses of soybean yield and biomass to growth at elevated CO2 concentrations and variation in growing season temperature and water inputs (precipitation plus irrigation). Growing season average temperature was not a good predictor of the magnitude of biomass and yield responses to elevated CO2, contradicting the prediction that responses to elevated CO2 would increase with increasing temperature due to the benefit from CO2 decreasing photorespiration and water loss. However, the prediction that the relative stimulation of yield by elevated CO2 would be greatest in dry conditions was generally supported. The results imply a simple CO2 fertilization value is not appropriate for modeling future crop productivity under varying environmental conditions. 04 Transphosphorylation of E. coli proteins during production of recombinant protein kinases provides a robust system to characterize kinase specificity. Protein kinase specificity is of fundamental importance to pathway regulation and signal transduction but is difficult to characterize. We developed a convenient system to monitor the activity and specificity of recombinant protein kinases expressed in E.coli by monitoring the autophosphorylation of the protein kinase and observed transphosphorylation of bacterial proteins catalyzed by the recombinant protein kinase. Using enrichment approaches followed by LC-MS/MS, phosphosites were identified allowing motifs associated with auto- and trans-phosphorylation to be characterized. The E. coli transphosphorylation assay can be applied broadly to protein kinases and provides a convenient and powerful system to elucidate kinase specificity and thereby advances research investigations on the stress sensitivity of crop yield. 05 Host and pathogen battle for control of tyrosine phosphorylation that are involved in plant pathogen defense responses. The phosphorylation of Tyrosine phosphorylation amino acids on a pathogen sensor receptor kinase known as EFR has been identified by ARS scientists working in collaboration with scientists at Norwich, UK that triggers plant immune responses to bacterial infections. The critical phosphotyrosine is targeted by pathogens like Pseudomonas syringae (Pst DC3000) that injects �effector proteins� into host cells, such as HopAO1, which has long been known to have phosphotyrosine phosphatase activity. However, the target of this activity was unknown and now appears to be Tyr-836 of EFR. Therefore, the host and pathogen battle for control of essential tyrosine phosphorylation on this sensor protein that turns on the plant defense system. This is first report where a tyrosine phosphorylation site(s) has been identified with a receptor kinase involved in innate signaling and shown to have functional significance in the plant. Fundamental understanding of receptor kinase signaling mechanisms could lead to development of crops with improved resistance to pathogens. 06 Canopy position has a profound impact on soybean seed nutrient composition. Soybeans are valued for their protein and oil content, but when used for human nutrition the content of minerals such as iron is also critically important. Although soybean seeds appear homogenous, the composition of mature seeds varies depending on the position on the main stem where the pods developed. Seed produced at the top of the canopy tend to have higher protein and less oil compared to seeds from the bottom of the canopy. While the concentration of many minerals does not vary with canopy position, iron concentration is generally 20% higher in seeds from the bottom of the canopy. Soy food products (soy flour, milk and okara) made from seeds from the top or bottom of the canopy reflect this difference in total seed iron concentration. Canopy position effects on seed iron concentration have been observed with diverse germplasm grown in the USA as well as cultivars grown in Africa. Knowledge of these canopy position effects could have immediate application for human health and nutrition in countries such as Africa where iron is limiting in the diet, and identifies potential targets for future improvement in soybean composition. 07 Limits on yields in the corn belt. ARS scientists in collaboration with a colleague at the University of Illinois at Urbana-Champaign used recent and projected increases of regional vapor pressure deficit to estimate limits on corn yield imposed by average rainfall now and in the future. Whereas current average rainfall can support yields up to 230 bushels/acre, by midcentury the same amount of precipitation will support only 175 bushels/acre due to the predicted warmer climate. The predicted increase in atmospheric carbon dioxide, which also decreases plant water loss, will mitigate only some of this decrease. 08 Predicted effects of climate change on soybean photosynthesis and productivity. In field experiments in which soybean crop canopies were warmed with or without an accompanying increase in the concentration of carbon dioxide it was discovered that the warming more than completely reversed the stimulation of photosynthesis by elevated carbon dioxide. The cause was shown to be the combined down regulation of photosynthetic capacity due to the increase in carbon dioxide and in temperature. It had been generally assumed that elevated carbon dioxide would at least off set the inhibition by warming but it appears that will not be the case as growing season temperatures continue to increase. This research indicates that current projections have how much increasing CO2 will be protected against the loss of yield due to warming temperatures are over optimistic and that greater genetic tolerance to warming needs to be discovered and breed into crop plants. 09 The relationship of legume crop (for example soybean) productivity and field scale photosynthesis. Net CO2 exchange data of legume crops at 17 flux tower sites in North America and three sites in Europe representing 29 site-years of measurements were evaluated. The analyses produced net CO2 exchange data and new legume crops determined at diurnal and weekly time steps. Comparison with the data from grain crops obtained with the same method demonstrated that field level photosynthesis of legumes were lower than those of maize but higher than for wheat crops. This research advances information about the mechanism by which crops can inject organic carbon into the soil and shows that those crops adding the most to soil carbon stores are those that have the highest field level photosynthesis rates.
Impacts
(N/A)
Publications
- Ort, D.R., Long, S.P. 2014. Limits on yield in the corn belt. Science. 344:484-485.
- Ruiz-Vera, U.M., Siebers, M., Gray, S., Rosenthal, D.M., Kimball, B.A., Ort, D.R., Bernacchi, C.J. 2013. Global warming can negate the expected CO2 stimulation in photosynthesis and productivity for soybean grown in the Midwest United States. Plant Physiology. 162:410-423.
- Rosenthal, D.M., Ruiz-Vera, U.M., Siebers, M.H., Gray, S.B., Bernacchi, C. J., Ort, D.R. 2014. Biochemical acclimation, stomatal limitation and precipitation patterns underlie decreases in photosynthetic stimulation of Soybean (Glycine max) at elevated [CO2] and temperatures under fully open air field conditions. Plant Science. 226:136-146.
- Bajwa, V.S., Wang, X., Blackburn, R.K., Goshe, M.B., Mitra, S.K., Williams, E.L., Bishop, G.J., Krasnyanski, S., Allen, G., Huber, S.C., Clouse, S.D. 2013. Identification and functional analysis of tomato BRI1 and BAK1 receptor kinase phosphorylation sites. Plant Physiology. 163:30-42.
- Hussain, M.Z., VanLoocke, A.D., Markelz, R., Siebers, M.H., Ruiz-Vera, U.M. , Leakey, A., Ort, D.R., Bernacchi, C.J. 2013. Future carbon dioxide concentration decreases canopy evapotranspiration and soil water depletion by field-grown maize. Global Change Biology. 19:1572-1584.
- Yendrek, C.R., Ainsworth, E.A., Thimmapuram, J. 2013. Method: The bench scientist's guide to RNA-Seq analysis. BMC Research Notes. 5:506.
- Locke, A.M., Sack, L., Bernacchi, C.J., Ort, D.R. 2013. Soybean leaf hydraulic conductance does not acclimate to growth at elevated [CO2] or temperature in growth chambers or in the field. Annals Of Botany. 112(5) :911-918.
- Gilmanov, T., Baker, J.M., Bernacchi, C.J., Billesbach, D.P., Burba, G.G., Castro, S., Eugster, W., Fischer, M.L., Gamon, J.A., Gebremedhin, M.T., Glenn, A.J., Griffis, T.J., Hatfield, J.L., Heuer, M.W., Howard, D.M., Leclerc, M.Y., Loescher, H.L., Matloie, O., Matamala, R., Meyers, T.P., Olioso, A., Phillips, R.L., Prueger, J.H., Skinner, R.H., Suyker, A.E., Tenuta, M., Wylie, B.K. 2014. Productivity and carbon dioxide exchange of the leguminous crops: Estimates from flux tower measurements. Agronomy Journal. 106(2):545-559.
- Oh, M., Wu, X., Kim, S.Y., Clouse, S.D., Huber, S.C. 2014. The Carboxy- terminus of BAK1 regulates kinase activity and is required for normal growth of Arabidopsis. Frontiers in Plant Physiology. DOI: 10.3389/fpls. 2014.00016.
- Macho, A., Schwessinger, B., Ntoukakis, V., Brutis, A., Segonzac, C., Roy, S., Kadota, Y., Oh, M., Sklenar, J., Huber, S.C., et al. 2014. A bacterial tyrosine phosphatase inhibits plant pattern recognition receptor activation. Science. 343:1509-1512.
- Oh, M., Wu, X., Huber, S.C. 2013. Impact of Ca2+ on structure of soybean CDPK� and accessibility of the Tyr-24 autophosphorylation site. Plant Signaling and Behavior. 8(12):e27671-1-5.
- Bishop, K.A., Leakey, A., Ainsworth, E.A. 2014. How seasonal temperature or water inputs affect the relative response of C3 crops to elevated [CO2]: A global analysis of open top chamber and Free Air CO2 Enrichment (FACE) studies. Food and Energy Security. DOI: 10.1002/fes3.44.
- Sun, J., Feng, Z., Ort, D.R. 2014. Impacts of rising tropospheric ozone on photosynthesis and metabolite levels on field grown soybean. Plant Science. DOI: 10.1016/j.plantsci.2014.06.012.
- Sun, J., Feng, Z., Leakey, A., Zhu, X., Bernacchi, C.J., Ort, D.R. 2014. Inconsistency of mesophyll conductance estimate causes the inconsistency for the estimates of maximum rate of Rubisco carboxylation among the linear, rectangular, and non-rectangular hyperbola biochemical models of leaf.... Plant Science. DOI: 10.1016/j.plantsci.2014.06.015.
- Koester, R.P., Skoneczka, J.A., Cary, T.R., Diers, B.W., Ainsworth, E.A. 2014. Historical gains in soybean (Glycine max Merr.) seed yield are driven by linear increases in light interception, energy conversion, and partitioning efficiencies. Journal of Experimental Botany. 65(12):3311- 3321.
|
|