Progress 06/01/24 to 05/31/25
Outputs
Target Audience: Knowledge on sulfur transporter function is essential for an overall understanding of how sulfur partitioning is regulated throughout the plant, and how this process is affecting sulfur, nitrogen and carbon acquisition, general plant metabolism, as well as growth and development. The information acquired is of high importance to a broad scientific audience including plant physiologists, cell biologists, biochemists, ecologists, and agricultural engineers, who are studying nutrient acquisition and cycling, atmospheric nitrogen fixation, sulfur use efficiency, primary and secondary plant metabolism, and sulfur, nitrogen and carbon distribution between plant organs. Understanding nutrient partitioning and sink/source relationships is also highly relevant for student education and training both in the research laboratory and classroom setting, as these students are the future scientists driving agricultural education and innovations. The studies will also be important for plant breeders, the agriculture industry, and farmers since alterations of sulfur partitioning processes may benefit plant growth, seed yield, and seed protein levels and quality. Strategies can potentially be developed to increase biomass and improve food production and security, including under environmental stress conditions. Changes/Problems: Overall, we continued to make strong progress towards our goals. We have generated new materials for analyses and made exciting discoveries on S allocation processes and their key role in atmospheric N fixation and legume growth and productivity. Much of the progress can be attributed to the graduate students that participated on the project. However, we had a major delay in hiring a qualified postdoctoral researcher. The foreign candidate we finally tried to employ (see previous project report) was unsuccessful with their visa application process. Thus, the position was readvertised and, happily, a highly experienced postdoctoral researcher from the US was successfully recruited by January 2025. Based on the deferred hiring of the postdoc of about 1.5 years, the timeline for the proposed research is likely affected and the project may require a no-cost extension. On the other hand, despite the hiring problems, we have been highly productive and made overall very good progress. In addition, a new Ph.D. student was recruited who will further contribute to the success of this project. What opportunities for training and professional development has the project provided? Three graduate students have been trained within the second year of this project in a broad range of aspects related to plant physiology and agronomy research. They gained research experience and learned about the organization of a laboratory, laboratory safety issues and methods, how to keep a lab notebook, the importance of weekly updates of literature searches, and how to prepare and present a scientific presentation. In addition, they were trained on how to design experiments, how to perform phenotypic, molecular, elemental, and biochemical analyses on the transgenic legume plants, and how to analyze the results. The students further learned through intensive discussions with the PDs how to critically evaluate, discuss and interpret the research results. The lead PD invested serious amount of time and efforts in mentoring, training, and educating her students. She held weekly one-on-one meetings as well as lab meetings that were frequently joined by the co-PD discussing the research project, literature and the current knowledge on plant metabolism and transport. The lead PD's office is in the corner of the lab so that she was always accessible to help planning and designing experiments, to analyze the results and to discuss their relevance for whole plant functions. She also provided considerable feedback on preparing power point presentations and oral presentations. Thus, two of the graduate students involved in this project publicly and successfully defended their graduate research. In addition, the lead PD supported the two students during the writing process of their doctoral dissertation or master's thesis for a spring (April 2025) and summer graduation (May 2025), respectively. Further, the PDs were successful in recruiting a postdoctoral researcher for the project, who started in January 2025. Supported by the PDs and the students in the Tegeder lab, the postdoc went during the first three months through an intensive training period to become familiar with the project, theoretically and practically. The experienced graduate students worked closely with the postdoc, training her on methods, protocols and plant growth procedures essential for the success of this project. This also helped to develop the students' communication and teaching skills. How have the results been disseminated to communities of interest? Results from this research have been discussed during an oral presentation at the international Biology Symposium at the University of Newcastle in Australia. In addition, this work has been conferred to the scientific community and the public through four talks by graduate students involved in the project, and during a poster presentation at the international Plant Biology 2024 meeting in Honolulu, Hawaii. Further, during the second reporting period, the PDs taught undergraduate courses in Introductory Biology (Biol. 106) and Plant Physiology (Biol. 420) as well as a graduate class on Plant Cell Biology (Biol. 537) at WSU. The classroom setting provided the opportunity to present and discuss the research data, making students aware that teaching at a university is not disconnected from fundamental research. The PDs also used the classroom to discuss research concepts and different approaches, and to encourage critical thinking. What do you plan to do during the next reporting period to accomplish the goals? 1. We obtained seeds of the newly produced SULTR-OE soybean lines and started segregation analyses to identify homozygous transgenic lines. Screening of these lines will continue up to the T4 generation. In addition, we will determine the transgene copy number for each line, select stable, single copy transgenic genotypes and obtain sufficient seeds for future investigation of the SULTR-OE soybean lines. 2. Significant efforts and resources will be directed towards the initial analysis of the OPT-OE soybean lines. Growth, molecular, biochemical and, if time allows, elemental analyses will be performed to gain insights on the importance of glutathione transport processes for soybean performance. 3. We will finalize the experiments on the MUP1 plants. Specifically, we will confirm obtained results on the role of S partitioning processes in biological N fixation in MUP1 nodules with an independently grown set of MUP1 plants. In addition, we will analyze in more detail the impact of enhanced methionine transport processes on seed development, the composition of seed storage proteins, and seed nutritional quality. We will also start to summarize the results in a manuscript. 4. Experiments for the MMP1 pea plants were finalized, and we will summarize and discuss the results in a manuscript for submission. If requested by the reviewers, additional experiments may need to be performed for final acceptance of the publication. Work on the MMP1 plants will also be summarized in the student's doctoral dissertation for a planned graduation in Fall 2025. 5. We will continue to train and mentor the new postdoc on the project and support her professional development. In addition, a new Ph.D. candidate has been recruited to the project with a starting date in Fall 2025. He will be made familiar with the theoretical background of this project and trained in basic methodology needed to address the project hypotheses and proposed research strategies.
Impacts
What was accomplished under these goals?
Following root uptake, sulfur (S) is transported from cell to cell or from source (e.g. roots or mature leaves) to sink organs (e.g. nodules or seeds) as sulfate. Alternatively, sulfate is assimilated in roots or leaves and mainly partitioned from source to sink either as methionine (Met), S-methyl-methionine (SMM) or glutathione (GSH). Nodulated soybean plants are analyzed that overexpress either an Arabidopsis sulfate (SULTR-OE) or GSH (OPT-OE) transporter, as well as pea plants that express either a yeast Met (MUP1) or SMM transporter (MMP1) to resolve the importance of S transport processes for legume nitrogen (N) fixation, physiology, growth, yield and seed nutritional quality. Objective 1: Role of S partitioning processes in biological N fixation in nodules (35% completion). S is critical for atmospheric N fixation that occurs in a symbiotic relationship with bacteria in root nodules. Soybean and pea with altered S transporter function are examined to resolve their importance for N fixation and legume development. As S assimilation and partitioning are directly linked to N and carbon (C) metabolism, we also investigate the significance of S transport processes for N and C availability and partitioning within legumes. SULTR-OE soybean plants: New SULTR-OE lines were produced at the Wisconsin Crop Innovation Center. We applied for, and were approved, a USDA-APHIS permit for interstate movement of SULTR-OE seeds to our lab by the end of 2024. Using seeds of the T1 generation, the newly hired postdoctoral researcher screened for the presence of the transgene. Plants from 5 lines were confirmed to carry the Arabidopsis AtSULTR transporter in their genome. T2 seeds, that are heterozygous or homozygous for the transgene, are currently used for the next round of screening and identification of homozygous lines. In addition, we found that AtSULTR is expressed in leaves of all 5 lines. OPT-OE soybean plants: Using seeds of the T4 generation, we confirmed the presence of the AtOPT transgene in the genome of 5 lines as well as their homozygosity for the transgene. In addition, all lines carried a single copy of AtOPT, and expression studies showed relatively high AtOPT transcript levels in all OPT-OE lines. We currently grow wild type (WT) plants, the 5 transgenic lines, and their segregating WT (segWT) in the greenhouse for seed amplification. The plants were also used for some preliminary analyses. Photosynthesis measurements indicate higher C fixation rates in the transgenic OPT-OE lines compared to WT and segWT plants. The OPT-OE plants also showed an increased growth phenotype that we are in the process to confirm by biomass measurement. We will then select for 2-3 lines and a segWT for detailed future analyses. MUP1 pea plants: Over the past year, a major focus was put on examining nodulated MUP1 lines expressing a methionine transporter. Analysis during vegetative growth phase demonstrated that MUP1 function positively affects overall S uptake, assimilation and source-to-nodule partitioning, leading to increased N fixation, nodule function, and nodule-to-leaf N transport. Increased leaf N supply enhanced leaf C assimilation and leaf-to-nodule C partitioning in support of N fixation. MUP1 plant development and growth were improved, and their S, N and C gains were increased. While these intriguing results remain to be confirmed with an independently grown set of MUP1 plants, our findings highlight the critical role of methionine transporters in regulating S, N and C acquisition and assimilation, and in S, N and C assimilate partitioning, ultimately contributing to pea growth under N-fixing conditions. MMP1 pea plants: We finalized the experimental work on the MMP1 pea plants to understand the role of SMM partitioning processes in biological N fixation in nodules. For example, analyses on organ S assimilation, nodule N assimilation, S and N transporter expression and source-to-sink metabolite partitioning were performed. We found that increased phloem loading of SMM by the MMP1 transporter controls S uptake, assimilation and partitioning to nodules and results in increased N fixation. The MMP1 plants move more N from nodules to shoot, which promotes leaf photosynthesis and subsequent C supply to nodules for growth and N fixation. These combined changes in nutrient acquisition and assimilate partitioning and organ supply ultimately result in increased growth and development of roots, nodules and shoots. Together, these data are exciting as they demonstrate that changes in source-to-sink transport of SMM improve the physiological performance and growth of pea plants and provide a promising strategy for the improvement of other crops. Our data are currently summarized in a manuscript for publication. Objective 2: Importance of S partitioning processes for seed nutritional quality in N-fixing legumes (30% completion). S (and N and C) availability not only affects development and yield of legume seeds but also the quality of specific seed storage proteins. Legumins, albumins, and glycinins are high-quality storage proteins in pea and soybean seeds, respectively as they are comparably rich in S-amino acids; however, their amount in seeds is low relative to other seed storage proteins that are poor in S. Our S transporter-overexpressing plants are analyzed to resolve if S partitioning processes to, and into, seeds impact seed development, S/C/N storage pools and quantities of S-rich proteins. MUP1 pea plants: Assimilates transported during reproductive phase from leaves to developing pea seeds require transporters localized to the outer epidermal cell layer of the seed cotyledons. RT-qPCR analysis confirmed that MUP1 is expressed in the transgenic cotyledons. In addition, expression of transporter genes involved in embryo import of amino acids as well as transcript levels of cotyledon S assimilation and methionine synthesis genes were upregulated in MUP1 seeds compared to WT. This suggests increased amino acid and sulfate supply of MUP1 seeds, and higher synthesis of S-containing amino acids within MUP1 seeds. Further, seed protein levels were significantly increased by around 22% in MUP1 versus WT seeds, expression of genes associated with the synthesis of S-rich as well as S-poor storage proteins was upregulated, and gel electrophoresis of soluble seed proteins revealed increases in all storage protein fractions in MUP1 seeds compared to WT, including the high-quality legumins and albumins. Finally, elemental analysis determined an increase in the %S and %N in the MUP1 seeds by up to 24%. This work provides strong evidence that methionine transport processes positively affect the seed number of pea plants and result in higher seed protein content and seed nutritional quality. MMP1 pea plants: We reconfirmed our previous results with an independently grown set of plants and finalized the experimental work on the MMP1 pea plants. Results showed that MMP1 plants produced more seeds per plant than WT resulting in a seed yield increase between 22-31%. Changes in S and N assimilate source-to-sink partitioning also led to an increase in MMP1 seed proteins by 12-17%. Together, this resulted in an impressive increase in seed protein yield per MMP1 plant of up to 57% compared to WT. Protein analysis also showed an increase in all storage protein fractions for MMP1 versus WT seeds, including the S-rich albumins and legumins, supporting that seed protein quality was improved in MMP1 seeds. Overall, this work demonstrates that the manipulation of SMM transporter function presents an important strategy for overcoming limitations in S supply to legume seeds and for improving seed protein levels and seed nutritional quality. These results are currently summarized and discussed in a manuscript for publication. Objective 3: Determine the role of S partitioning processes in N-fixing legumes under S deficiency (planned for Project Year 4).
Publications
- Type:
Theses/Dissertations
Status:
Awaiting Publication
Year Published:
2025
Citation:
Thu S.W. 2025. The role of nitrogen transport processes in soybean (Glycine max [L.] Merr.) physiology and stress response. Doctoral dissertation, April 2025, Washington State University.
- Type:
Theses/Dissertations
Status:
Awaiting Publication
Year Published:
2025
Citation:
Campbell E. A. 2025. Role of methionine transporter function in sulfur partitioning and source-sink physiology of nodulated pea (Pisum sativum L.) plants. Master's thesis, May 2025, Washington State University.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Tegeder M. 2024. Understanding photoassimilate transport processes in plants. 50th Anniversary of Biology Symposium, University of Newcastle, November 4-5th, Newcastle, Australia (invited; virtual)
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2025
Citation:
Campbell E. A. 2025. Role of sulfur transport processes in pea nodule function and seed development. Graduate Research Symposium, February 21st. Washington State University, Pullman, WA, USA.
- Type:
Other
Status:
Published
Year Published:
2024
Citation:
Thu S.W. 2024. Physiological relevance of nitrogen transport processes in soybean. School of Biological Sciences Seminar Series, November 4th. Washington State University, Pullman, WA, USA.
- Type:
Other
Status:
Published
Year Published:
2025
Citation:
Campbell E. A. 2025. Impact of methionine transport processes on sulfur partitioning and physiology of nodulated pea plants (Pisum sativum L.). Seminar at The Cluster of Excellence on Plant Sciences, March 12th, University of Cologne, Cologne, Germany (virtual).
- Type:
Other
Status:
Published
Year Published:
2025
Citation:
Campbell E. A. 2025. Role of methionine transporter function in sulfur partitioning and source-sink physiology of nodulated pea (Pisum sativum L.) plants. School of Biological Sciences Seminar, April 15th. Washington State University, Pullman, WA, USA.
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Progress 06/01/23 to 05/31/24
Outputs
Target Audience: Knowledge on sulfur transporter function is essential for an overall understanding of how sulfur partitioning is regulated throughout the plant, and how this process is affecting sulfur, nitrogen and carbon acquisition, general plant metabolism, as well as growth and development. The information acquired is of high importance to a broad scientific audience including plant physiologists, cell biologists, biochemists, ecologists, and agricultural engineers, who are studying nutrient acquisition and cycling, atmospheric nitrogen fixation, sulfur use efficiency, primary and secondary plant metabolism, and sulfur, nitrogen and carbon distribution between plant organs. Understanding nutrient partitioning and sink/source relationships is also highly relevant for student education and training both in the research laboratory and classroom setting, as these students are the future scientists driving agricultural education and innovations. The studies will also be important for plant breeders, the agriculture industry, and farmers since alterations of sulfur partitioning processes may benefit plant growth, seed yield, and seed protein levels and quality. Strategies can potentially be developed to increase biomass and improve food production and security, including under environmental stress conditions. Changes/Problems: Overall, we made strong progress towards our goals and have generated very exciting results that are in strong support of our working hypothesis that S allocation processes are key for C/N metabolism, and source/sink relationships. The progress has mainly been made possible because the two senior PhD students involved in the project had already extensive research experience and are well trained in growing, handling and analyzing pea and soybean plants in the greenhouse. However, we had two unexpected setbacks over the course of the last year. First, there were significant problems in finding a highly qualified postdoctoral researcher at the beginning of the project. And once we identified an excellent candidate, the hiring process was delayed, and is still ongoing, due to visa issues. We plan to re-advertise the postdoc position during summer 2024 to have an alternative strategy in place if the current candidate is unsuccessful with their visa application process. The graduate students were also supposed to train the new postdoctoral researcher during the past year, especially with respect to the highly critical plant growth and care practices. We still anticipate that the postdoc hire is soon successful to facilitate a smooth transition before the PhD students graduate in fall 2024. Otherwise, it is likely that future progress on the project is delayed. Second, we were only able to obtain one stable SULTR-OE line and had to produce additional lines at the Wisconsin Crop Innovation Center (WCIC). Seeds from the new lines are expected to be available by September 2024, but they will first need to be screened to obtain stable SULTR-OE lines. Therefore, we expect that the functional analyses of the SULTR-OE lines (Objectives 1 to 3) are delayed by at least one year. Yet, despite the problems with hiring a postdoctoral researcher and the unexpected issues with the SULTR-OE lines delaying their analysis, we have been very productive during the first year of funding and made overall good progress. What opportunities for training and professional development has the project provided? Three female graduate students have been trained within the first year of this project in a broad range of aspects related to plant physiology and agronomy research. They gained research experience and learned about the organization of a laboratory, laboratory safety issues and methods, how to keep a lab notebook, the importance of weekly updates of literature searches, and how to prepare and present a scientific presentation. In addition, they were trained on how to design experiments, how to perform phenotypic, molecular, elemental, and biochemical analyses on the transgenic legume plants, and how to analyze the results. The students further learned through intensive discussions with the PDs how to critically evaluate, discuss and interpret the research results. Further, the two more experienced PhD students worked closely with a new MS student, who started in fall 2023, and took part in mentoring and supervising the student. This helped to develop the PhD candidates' communication and teaching skills. The lead PD invested serious amount of time and efforts in mentoring, training, and educating her students. She held weekly one-on-one meetings as well as lab meetings that were frequently joined by the co-PD discussing the research project, literature and the current knowledge on plant metabolism and transport. Both PDs also provided considerable feedback on preparing power point presentations and oral presentations. The lead PD's office is in the corner of the lab so that she was always accessible to help planning and designing experiments, to analyze the results and to discuss their relevance for whole plant function. How have the results been disseminated to communities of interest? Results from this research have been discussed during a research exchange visit and a seminar at the VIB-UGent Center for Plant Systems Biology, University of Ghent, Belgium. Further, during the first reporting period the PDs taught undergraduate courses in Introductory Biology (Biol. 106) and Plant Physiology (Biol. 420) as well as a graduate class on Plant Stress Physiology (Biol. 517) at WSU. The classroom setting provided the opportunity to present and discuss the research data, making students aware that teaching at a university is not disconnected from fundamental research. The PDs also used the classroom to discuss research concepts and different approaches, and to encourage critical thinking. What do you plan to do during the next reporting period to accomplish the goals? Our plans for the next reporting period are: 1. Obtain the seeds of the newly produced SULTR-OE soybean lines, grow multiple generations in the greenhouse while performing segregation analyses, and determine the transgene copy numbers to identify stable, single copy transgenic lines for further investigation. 2. Initiate experiments with the stable OPT-OE soybean lines and obtain preliminary results on effects on growth (e.g. shoot, root and nodules), S metabolism and partitioning (e.g. expression and metabolite analyses) and plant total S, N and C gain (i.e. elemental analyses). 3. Continue our analyses with the MUP1 pea plants: Current results will need to be confirmed with an independently-grown set of plants and additional molecular, biochemical, and physiological analyzes of MUP1 lines will be performed to understand the role of methionine transport processes in biological N fixation, and if and how alterations in S partitioning affect (i) primary metabolism, (ii) S/N/C assimilate partitioning, and (iii) plant growth. 4. Finalize the work on the MMP1 pea plants to understand the role of SMM partitioning processes in biological N fixation in nodules and for seed nutritional quality and prepare a manuscript. Many of our discoveries have now been confirmed in independent experiments and were finalized. However, we still need to reconfirm data obtained with respect to organ S assimilation, nodule N assimilation, S and N transporter expression and source-to-sink metabolite partitioning. We will also need to more specifically address effects on seed physiology and, for example, perform additional analyses with respect to seed S content and protein quality. 5. Hire as soon as possible a knowledge postdoctoral researcher to guarantee smooth continuation of the project and its success (see Changes/Problems).
Impacts
What was accomplished under these goals?
Following root uptake, S is transported from cell to cell or from source (e.g. roots or mature leaves) to sink organs (e.g. nodules or seeds) as sulfate. Alternatively, sulfate is assimilated in roots or leaves and mainly partitioned from source to sink either as methionine (Met), S-methyl-methionine (SMM) or glutathione (GSH). S transporters are assumed to play a central role in legume physiology, but their function in S movement among source/sink tissues is poorly understood. We will analyze nodulated soybean plants that overexpress either a plant sulfate (SULTR-OE) or GSH (OPT-OE) transporter, as well as pea plants that express either a yeast Met (MUP1) or SMM transporter (MMP1) to resolve the importance of S transport processes for legume nitrogen (N) fixation, physiology, growth, yield and seed nutritional quality. Objective 1: Role of S partitioning processes in biological N fixation in nodules (20% completion). S is critical for atmospheric N fixation that occurs in a symbiotic relationship with bacteria in root nodules. Soybean and pea with altered S transporter function are investigated to resolve their importance for N fixation and legume development. As S assimilation and partitioning are directly linked to N and carbon (C) metabolism, we also investigate the significance of S transport processes for N and C availability and partitioning within legumes. SULTR-OE soybean plants: Two SULTR-OE lines were recently produced at the Wisconsin Crop Innovation Center (WCIC) and now grown up to the T4 progeny while performing segregation analyses to select for stable transgenic lines. One of these SULTR-OE lines is stable; it expresses the transgene and can therefore be used for future studies. However, the second line continues to segregate, suggesting that the T-DNA has generated an unspecific insertion mutation that disrupted a vital endogenous gene. Because analysis of only one line is insufficient for drawing informed conclusions on the genetic manipulation, we ordered additional transgenic SULTR-OE lines at the WCIC. At least 10 new lines were produced up to now and are currently grown at the WCIC to obtain T1 seeds. We already applied for a USDA-APHIS permit for interstate movement of the transgenic seeds to our lab in late summer. OPT-OE soybean plants: We also performed segregation analyses for the OPT-OE plants and obtained 5 potentially homozygous lines. We used Agrobacterium rhizogenes to produce these lines, which has a 40-50% likelihood to result in a single or low copy number of the transgene(s). Current results suggest insertions of a maximum of two transgenic copies in the soybean genomes, and quantitative polymerase chain reaction showed transgene expression. MUP1 pea plants: We have two stable transgenic lines available for this expression construct. Phenotypic analyses were performed with these N-fixing MUP1 plants, and results confirmed significant increases in shoot and root biomass. In addition, individual nodule dry weight and size were reduced while nodule numbers per plant were strongly increased. Together, the data support that Met transporter function affects development and growth of pea nodules, shoots and roots which is most likely associated with physiological changes in source and sink organs. In fact, preliminary analyses of elemental S and sulfate levels, and amino acid content in the xylem sap suggest adjustments in both S and N (and most likely C) metabolism and altered partitioning processes at the whole plant level. Overall, the current data are intriguing as they strongly support that alterations in Met partitioning provide pea plants with an advantage and lead to an improved physiological performance and growth. MMP1 pea plants: A major research focus during the last year was placed on the analysis of 2 stable MMP1 lines expressing an SMM transporter. Results showed increases in shoot, root, and nodule biomass, suggesting a positive effect on N fixation in support of growth. In addition, the nodule number was significantly increased by 40-42%. Further, analysis of MMP1 xylem sap showed enhanced Met movement from nodulated roots to shoot as well as increased sulfate and GSH partitioning. Expression of some S assimilation and metabolism genes was slightly upregulated in MMP1 nodules compared to wild type. This points to increased S assimilation in nodules and enhanced availability of organic S for the synthesis of S-rich enzymes required for N fixation. In addition, upregulation of N assimilation and transporter genes, as well as an increase in nodule to shoot N partitioning suggest that the MMP1 nodules fix more N for increased shoot N nutrition. Leaf C fixation requires high amounts of N and photosynthesis rates were improved in MMP1 plants further supporting enhanced N partitioning to shoots/leaves. Increased C fixation was further corroborated by elevated sucrose phloem levels and delivery to nodules. Together, our data demonstrate the importance of S transport processes to efficiently coordinate physiological functions and pea development. We discovered that changes in S partitioning in N-fixing MMP1 plants positively affect pea growth, nodule S metabolism and related N and C metabolic processes in source and sink. The overall outcome already shows that the MMP1 expression approach results in major improvements in S, N, and C gains at the whole plant level. Objective 2: Importance of S partitioning processes for seed nutritional quality in N-fixing legumes (15% completion). S (and N and C) availability not only affects development and yield of legume seeds but also the quality of specific seed storage proteins. Legumins and albumins, and glycinins are high-quality storage proteins in pea and soybean seeds, respectively as they are comparably rich in S-amino acids; however, their amount in seeds is low relative to other seed storage proteins that are poor in S. Our S transporter-overexpressing plants are analyzed to resolve if S partitioning processes to, and into, seeds impact seed development, S/C/N storage pools and quantities of S-rich proteins. MUP1-pea plants: The two N-fixing MUP1 lines were grown in the greenhouse to maturity to investigate the effects of altered Met transport processes on seed yield. The data showed an up to 33% increase in seed yield for the MUP1 plants compared to the wild type. In addition, seed protein levels were enhanced by around 29% though it remains to be examined to what extend amounts of S-rich proteins are affected. While these results need to be confirmed with an independently grown set of plants, they provide strong evidence that Met transport processes are essential for pea productivity, positively affect the seed number per plant and result in higher seed protein content. MMP1 pea plants: Seed analysis of MMP1 plants revealed higher yields of up to 31% in transgenic plants compared to wild type. These increases were due to significantly higher seed numbers while no changes in individual seed weights were observed. In addition, protein levels were significantly higher in MMP1 versus wild-type seeds leading to an overall improvement in seed protein yield per plant of around 50%. Seed protein content was analyzed using stained SDS-PAGE gels and results showed a general increase in storage proteins. This indicates that in MMP1 seeds not only S-poor proteins such as vicilin or convicilin are elevated but also S-rich storage proteins (i.e. legumins and albumins). The data further implies that increased source-to-sink movement of SMM triggers enhanced synthesis of S-rich proteins in seeds. Overall, this work demonstrates that SMM transporter function presents a bottleneck in S allocation to seeds and that its targeted manipulation is a powerful tool for overcoming limitations in the accumulation of high-quality seed storage proteins. Objective 3: Planned for Project Year 4.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Tegeder M. Strategies for crop improvement. VIB-UGent Center for Plant Systems Biology, Ghent, Belgium,
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