Progress 02/01/18 to 08/31/21
Outputs
Target Audience:Target audiences International plant and crop research community: We presented a poster (invited) at the Gordon Research Conference in June 2018 on this project. We also presented (graduate student poster and a short talk) at the 11th Symposium of the International Society of Root Research in May 2021. National plant biology research community: We gave oral and poster presentations at the regional meetings of the American Society of Plant Biologists in March 2018, 2019 (cancelled due to Covid-19) and 2020. The PI also presented talks at Mississippi State University in Jan 2019 and at Texas Tech University in Feb 2019 on this project. The graduate student presented a poster at the SDSU Plant Science Symposium in October 2021 on this project. Undergraduate students: Teaching: I included hydrotropism (our project) in one of the Plant Physiology (BOT 327) lectures and designed class activities to discuss potential mechanisms based on other tropisms that students learned from the class. Students are mostly majoring in Agronomy, Plant Sciences and Horticulture. Research: We trained 6 undergraduate researchers majoring in Biology and Microbiology in the lab, including three minority students. They conducted hydrotropism measurement and analyzed the data in the lab. Graduate students: Teaching: I discussed the research project in the Molecular Plant Physiology class (BIOS/PS 664). Research: I recruited and trained a graduate researcher (PhD) who is now preparing manuscripts for publication and his dissertation for defense. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Postdoctoral researcher Yafang Wang traveled to Iowa State University to present a research poster on this project. MS, now a PhD student Muyu Gu joined the project in 2019 participated in redesigning and constructing Hydrotropism Analyzers. He also worked with the PI and Dr. Don Auger, a coPI on the project, in the field in the summer to propagate corn seeds needed for this project. He has been working with the PI and Dr. Jixiang Wu, another coPI on this project, to optimize root growth and image analysis in the greenhouse and to be trained to conduct quantitative genetics and statistical analysis. He traveled to University of Nebraska-Lincoln for a workshop/symposium to learn single cell gene expression. I worked with six undergraduate students, Haileselassie Tefera, Yongjun Kim, Brooke Buthe, Janani Perera, Hunter Eide, and Karlee Albert on literature reading, proposal development, and poster presentation. Lab technical training and data analysis was provided by the graduate student. How have the results been disseminated to communities of interest?We have presented our research project and preliminary data at various conferences of professional societies. We have also included this research in classroom teaching and prepared a Youtube video for perspective students and their parents. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1: Identify Quantitative Trait Loci (QTLs) associated with various processes in hydrotropism: (100% Accomplished) We constructed 10 units of our novel Hydrotropism Analyzer that was incorporated with many improvements to achieve high durability, easy operation, and greater uniformity. We videotaped and analyzed >800 primary roots of maize and other species with the Hydrotropism Analyzer under various conditions (different relative humidity in the chamber, different lights, different distance between roots and water source, etc). We found that a relative humidity of 45-65% in the chamber, a distance of 2 mm from the root to the wet pad, and root exposure to greenlight were optimal for analysis of hydrotropism in the primary root of maize. The Hydrotropism Analyzers with optimized procedures were used to videotape the hydrotropic response of the two maize NAM populations which contain more than 250 recombinant inbred lines (RILs). Seeds were propagated over two summers. A total of 1,345 recorded videos and 2,690 images of these lines were analyzed to obtain all the quantitative data on hydrotropic response in the primary root of maize. Six parameters including Time to Initiate Bending (Ti), Time from Initial Bending to Touching water source (TtT), Total Time for hydrotropic response (TT), Final Root Angle (FA), Root bending Angle per hour (FA/TtT), and Root Elongation Rate (ER) were used to quantify the hydrotropic response process. Six QTL were finalized in the Oh43 NAM population, and QTLs were distributed across maize chromosomes 1, 2, and 6. Ten QTLs were identified in the Hp301 NAM population, distributed across chromosomes 3, 4, 5, 6, 9, and 10. The SNP markers near the QTL peak position were identified, and maize B73 reference genome was used to search for the candidate genes (within 1 cM genetic distance flanking the QTL peak) associated with hydrotropic response in the primary root of maize. The raw candidate genes list is available upon request. The top genes with their possible functions in hydrotropic response will be further investigated. These results will contribute to the science community by further understanding the underlying molecular pathway of hydrotropism in the root. Impact: We developed a robust system and standardized procedures for hydrotropism analysis in the primary root. This system allowed us to successfully evaluate the hydrotropic response in two maize NAM populations and has identified several QTL related to the hydrotropism in a major crop plant for the first time. The QTL and candidate genes identified may help us further reveal the underlying molecular mechanisms of hydrotropic response. Identification of the hydrotropism-related genes can potentially benefit breeding programs for selecting more drought tolerant maize genotypes. Objective 2: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. (100% Accomplished) Hydrotropism has been proposed to play an important role in drought tolerance. The evidence to support this claim, however, is lacking. This is partially due to the technical challenge in establishing a moisture gradient in the soil and the interference of gravitropic response and hydro-patterning (rapid production of lateral roots toward the moister area) in a soil with heterogenous moisture. In addition, the genotypes that differ in hydrotropic response are unavailable. The QTL analysis in Objective 1 allowed us to identify contrast lines in each parameter that can be used to compare their drought tolerance. We first established a hydrotropic inducing system using potting soil in square Petri dishes (soil-in-Petri dish system). This system simulated the soil condition with moisture heterogeneity and drought stress under natural environment. The system can reproducibly induce hydrotropism but separate hydro-patterning from hydrotropic response. We finalized the soil-in-Petri dish system after testing seedlings in 500 Petri dishes. In this system, there are three zones: the top and the bottom are well-watered zones and the middle zone is heterogenous in moisture. The young seedlings with primary roots 0.5 cm in length were transplanted into the top zone. When the primary roots grew through the middle zone, only the roots that showed hydrotropism were able to follow the water, reaching the well-watered bottom zone and surviving. The Petri-dish system was placed in a large growth chamber with a relative humidity of 60% and 16/8 d/n light cycle. Plants were harvested 7 days after transplanting. Images were taken daily and shoot growth was measured every 24h. Pictures were also taken at 7 d to show whether the primary root can track the moisture in the middle zone. We also collected other data such as survival rate of the primary root, length of the primary root, length of the lateral roots, length of each leaf, length of stem, fresh and dry weight of the shoot, node number, leaf number, primary root and bending angle of the primary root. Interestingly, we found that the survival rate of primary roots dictates other physiological performance or parameters. We then assayed inbred lines that differed in hydrotropic response in the 6 parameters determined by the Hydrotropism Analyzer in Objective 1. Our preliminary analysis showed Root Final Angle was the best to correlate with primary root survival in petri dish system. We thus focused on this parameter for more studies. We selected contrast lines with the greatest Root Final Angle (i.e. sharp bending toward water source, Group 1) or the smallest Root Final Angle (i.e. slow bending toward water source, Group 2) for comparison in the Petri dish system. The contrasting lines selected had similar root elongation rate determined by our hydrotropism analyzer. The primary root survival rate for Group 1 was 95.2% (20/21 plants) and Group 2 was 41.6% (10/24 plants). Chi-square test for primary roots survival ratio was performed between the two groups and the p-value was 0.00091, indicating the primary roots with larger bending angles (stronger hydrotropic response) showed significantly greater chance of survival compared to the roots with smaller bending angle. Welch two sample t-test were used to compare the overall plant performance between the two groups. Our results showed that plants in Group 1 were able to maintain 99% of the Shoot Fresh weight (SFW) and 98.2% of the Shoot Dry Weight (SDW) compared with the well-watered control plants, while plants in Group 2 were only able to maintain 73.6% of the Shoot Fresh weight and 79.1% of the Shoot Dry Weight. The differences between two groups were significant with the p-values <0.0001 for both SFW and SDW. Similarly, we found that the shoot and leaf growth were significantly different between two groups. The plants in Group 1 were able to maintain 100% Stem length, 93.7% 1st leaf length, 95.6% 2nd leaf length, 92.9% 3rd leaf length, while the plants in Group 2 were only able to maintain 93.6%, 94.1%, 81.8%, 68.5% for the above parameters, respectively (P values <0.001). Interestingly, we found that the seminal roots (length and fresh weight) between the two groups showed little difference (p value = 0.91) in our Petri-dish system. The results suggest that the primary root plays a much more important role during maize early seedling development compared to the seminal roots. Impact: Our novel soil-in-Petri dish system is sensitive enough to detect the difference in hydrotropic response among the genotypes that were identified using our Hydrotropism Analyzer, suggesting the effectiveness of the Hydrotropism Analyzer. We have provided the strong evidence to support the biological significance of hydrotropism in soils that are heterogenous in water moisture at the seedling stages. Our work warrants further studies on how hydrotropism impacts plant performance in field conditions and whether enhanced hydrotropism can improve crop drought tolerance.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Gu, M., Y. Wang, J. Wu, Y. Wu. 2021. Identification of QTLs associated with hydrotropism in the primary root of maize. University of Missouri - 11th Symposium of the International Society of Root Research. Online. May 25.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2021
Citation:
Gu, M., Y. Wang, J. Wu, Y. Wu. 2021. Hydrotropism in the primary root of maize. University of Missouri - 11th Symposium of the International Society of Root Research. Online. May 25.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Gu, M., Y. Wang, J. Wu, Y. Wu. 2021. Identification of QTLs associated with hydrotropism in the primary root of maize. University of Nebraska - Plant Science Symposium. Lincoln, NE. October 22.
|
Progress 02/01/20 to 01/31/21
Outputs
Target Audience:The target audiencesfor this project included the following: Undergraduate students: Teaching: I included hydrotropism in one of the Plant Physiology (BOT 327) lectures in March 2020 and April 2021, and designed class activities to discuss potential mechanisms based on other tropisms that students learned from the class. Students are mostly majoring in Agronomy, Plant Sciences and Horticulture. Research: We completed training one undergraduate researcher majoring in Biology in the lab in Aug 2019 - May 2020. She presented a poster in April 2020 as her capstone project along with a research thesis. Graduate students: Teaching: I discussed the research project in the Molecular Plant Physiology class (BIOS/PS664). Research: One graduate student (PhD) was supported by the grant and worked on the project last year and completed most of the planned experiments. Changes/Problems:The Covid-19 pandemic disrupted lab work during early 2020. What opportunities for training and professional development has the project provided?PhD graduate student Muyu Gu. He has been working with the PI and Dr. Jixiang Wu, another coPI on this project, to optimize root growth and image analysis in the greenhouse and in the lab. He was trained in and has explored various QTL analysis tools, and is now a very skilled researcher on QTL analysis. Undergraduate student Janani Perera I worked with the student on her capstone projects, trained her to write a research report and prepare a research poster. Lab technical training was partially provided by the graduate student on this project. How have the results been disseminated to communities of interest?We have included this research in classroom teaching. Planned conference presentation was cancelled. What do you plan to do during the next reporting period to accomplish the goals?Goal One: Identify quantitative trait loci (QTLs) associated with various processes in hydrotropism: Identify the candidate genes underlying the QTL and examine potential epistasis interactions between the genes underlying different QTL. Propose a hypothetical model or pathway for hydrotropism using the candidate genes identified. Summarize the results for the QTL analysis of the two NAM populations and prepare for publication. Goal Two: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. Compare the contrasting lines for their hydrotropic response using the Soil-in-Petri dish system and determine the correlation between hydrotropic response and drought tolerance. Compare the contrasting lines (20 lines total) for their hydrotropism and drought tolerance using the Soil-in-Petri dish system. We will complete the experiments by the end of June 2021. Analyze all the data collected from the contrasting line comparison experiments by the end of July 2021. Summarize all the results from Obj.1 and Obj.2, and complete one of the manuscripts by the end of August 2021. Submit a final report in September 2021.
Impacts
What was accomplished under these goals?
Goal One: Identify quantitative trait loci (QTLs) associated with various processes in hydrotropism: (100% Accomplished) We measured an additional 400 maize roots with our hydrotropism analyzer under various conditions. These extra tests and data analysis led to a standardized protocol for an improved data analysis. One challenge in hydrotropism measurement is that some roots behave very differently, showing a wavy pattern which significantly impacts some of parameters that we are quantifying. The other challenge is that some roots in the same genotype can vary drastically in hydrotropic response. The question is whether these variations are due to physical differences among the hydrotropism analyzers or true biological differences among the seedlings. Through various testing of our analyzers and grouping the data in various ways before QTL analysis, such as separating the wavy roots from the non-wavy roots, we were able to reproducibly identify several QTL with higher LOD values (see below), indicating a higher confidence on these QTL. We then re-visited and re-analyzed all the 1,345 videos of hydrotropism measurement for the two maize NAM populations using this new protocol. This new protocol allows us to separate a small group of roots behaving highly differently from the others in the dataset. The resulting new dataset was used for statistical and QTL analysis. We have eliminated a few QTL from previous versions and finalized our QTL results for both maize NAM (Nest Association Mapping) populations. A total of 6 QTL were finalized in the Oh43 NAM population, and the QTL were distributed across maize chromosomes 1, 2, and 6. A total of 10 QTLs were finalized in the Hp301 NAM population, and they were distributed across maize chromosomes 3, 4, 5, 6, 9, and 10 for the traits discussed below. The SNP markers near the QTL peak position were identified and maize B73 reference genome was used to search for the candidate genes (within 1 cM genetic distance flanking the QTL peak) associated with hydrotropic response in the primary root of maize. The candidate gene search is nearly completed and will be available upon request. The top genes with their possible functions in hydrotropic response will be investigated in the future. Hydrotropism is a complex biological process. The major challenge in the field is how to quantify this process. With our hydrotropism analyzer, we have established a robust evaluation system to assess various parameters in hydrotropism, including Time to Initiate Bending (Ti), Time from Initial Bending to Touching (TtT), Total Time for Hydrotropic Response (TT = Ti + TtT), Final Root Angle (FA), Root Bending Rate (FA/TtT), and Root Elongation (ER). We found that the smallest of Ti, TtT, or TT or the greatest of FA, FA/TtT, or ER were correlated to a greater extent with root hydrotropism. This allowed us to successfully identify 20 contrast lines (genotypes) in the two NAM populations for various parameters in hydrotropic response. These lines will be assayed in Objective 2. Impact: Our new streamlined protocol decreases the variation of our datasets and improves the confidence for the QTL identified. While most of the QTL are consistent with the ones identified previously using the raw dataset, the QTL now have greater LOD values (logarithm of the odds: indicate the chance of a putative QTL). With fewer but more confident QTL, we can concentrate on the true candidate genes in hydrotropic response. This goal was impacted by three factors that caused some delay: 1) In order to understand the approximately 10% unexplained variations in the QTL using the raw dataset for two NAM populations, we performed additional experiments as a verification in our hydrotropism analyzer. Additional experiments and videos/images analysis took time to finish; 2) Re-analysis of all the 1,345 videos for both NAM populations and processing the data were extremely time-consuming; 3) QTL analysis was done with multiple QTL analysis methods and software to improve the confidence on the QTL identified. Since the detection of reliable QTL is so important and will impact all future studies, the extra time we took to reanalyze our original data is necessary and justified. Goal Two: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. (75% Accomplished) We have established and optimized a system (Soil-in-Petri dishes) to consistently induce hydrotropism. The system simulates the soil condition with moisture heterogeneity under drought stress. This system can separate hydro-patterning from hydrotropic response in maize seedlings, and thus enables us to evaluate the association between hydrotropism and drought tolerance during the very early developmental stage of maize. Various parameters, such as root length, shoot length, and shoot fresh weight were assessed to quantify the outcome of hydrotropism in the Soil-in-Petri dish system. We have finalized 20 contrast lines (10 weak and 10 strong hydrotropic response) based on six hydrotropism parameters determined in objective 1. Currently, we are assaying these lines using the Soil-in-Petri dish system. Impact: We examined the performance of young maize seedlings in soil (potting mix) conditions. Our preliminary data showed that the seedlings with primary roots reaching the water through hydrotropism show greater plant height, primary root length, number of lateral roots, length of lateral roots, plant fresh weight, and leaf length. The indicates that primary roots with strong hydrotropism will benefit the plant health and production during the early stage of development under drought stress conditions. The Soil-in-Petri dish system will be a good system to complement our hydrotropism analyzer in the lab and to verify hydrotropic response. The system can potentially be used to screen for drought tolerant genotypes. This goal was impacted by two factors that caused some delay: 1) In order to establish a reliable moisture gradient that allows us to induce hydrotropism of primary root in the soil, we have tested a great number of designs and combinations of various moisture contents in the Soil-in-Petri dish system; 2) The COVID-19 pandemic in 2020 led to a few months of disruption of our work in the lab due to the campus closure.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Gu M, Wang Y, Auger D, Wu J, Wu Y. 2020. Identification of QTL associated with hydrotropism in maize primary roots. March 21-22. University of Illinois. Urbana-Champaign, IL. (The meeting was canceled due to the COVID19 pandemic)
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2020
Citation:
Perera J, Gu M, Wu Y. 2020. Identification of the location of moisture sensing in the primary toots of red bean seedlings. Capstone Project, April 2020. Brookings, SD.
|
Progress 02/01/19 to 01/31/20
Outputs
Target Audience: International plant and crop research community: We published a peer-reviewed research paper in a high impact plant journal (New Phytologist) in March 2020. National and regional plant biology research community: We published one poster abstract at the annual meeting of the South Dakota Science Academy in March 2019. I also presented a talk at Texas Tech University in Feb 2019 on this project. Undergraduate students: Teaching: I included hydrotropism (our project) in one of the Plant Physiology (BOT 327) lectures in April 2019 and designed class activities to discuss potential mechanisms based on other tropisms that students learned from the class. Students are mostly majoring in Agronomy, Plant Sciences and Horticulture. Research: we completed training two undergraduate researchers majoring in Biology in the lab in April 2019. One student continued working my lab in the summer 2019 after graduation. A new undergraduate student stared to work in the lab last year as her capstone project. She has finished her research proposal and is now working on the report. She will present a poster in April 2020 on campus. Graduate students: Teaching: I discussed the research project in the Molecular Plant Physiology class (BIOS/PS664). Research: One graduate researcher (MS) was supported by the grant and worked on the project last year and completed most of the planned experiments. Postdoc: A postdoc worked part time on the project and helped publish the first research paper. The postdoc also trained the graduate and undergraduate students in the lab. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Postdoctoral researcher Yafang Wang helped train graduate and undergraduate students and was involved in manuscript preparation, revision, and submission. She planned to go to two conferences to present her research. Unfortunately, both meetings were cancelled due to severe weather or the covid-19 situation. MS graduate student Muyu Gu was co-trained by the PI and Dr. Don Auger, a coPI on the project, in the corn field in the summer to propagate corn seeds needed for this project. He has been working with the PI and Dr. Jixiang Wu, another coPI on this project, to optimize root growth and image analysis in the greenhouse and in the lab. He was trained in and has explored various QTL analysis tools, and is now a very skilled researcher on QTL analysis. I worked with three undergraduate students, Haileselassie Tefera, Yongjun Kim, and Janani Perera on their capstone projects. I trained Haileselassie Tefera and Yongjun Kim to write a research report and prepare a research poster. I worked with Janani on literature reading and proposal development. Lab technical training was partially provided by the postdoc and graduate student. Janani has now completed data analysis and her research poster. How have the results been disseminated to communities of interest?We have presented our research project and preliminary data at various conferences and a journal publication. We have also included this research in classroom teaching. What do you plan to do during the next reporting period to accomplish the goals?Goal One: Identify quantitative trait loci (QTLs) associated with various processes in hydrotropism: Identify the candidate genes related to each QTL using the maize genome sequence information. Wrap up all the QTL analysis and prepare the data for publication. Goal Two: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. We will compare contrasting lines for their hydrotropic response using the soil-in-petri dish system and determine the correlation between hydrotropic response and drought tolerance. We will finalize the soil conditions for the hydrotropism test in petri dish conditions and assess the parameters to be used for evaluation of the relationships between hydrotropism and drought tolerance using a hybrid genotype by June 2020. We will complete the first batch of the contrasting lines identified based on the phenotypic data from two NAM populations for drought tolerance by August 2020. We will complete the second batch of the contrasting lines based on the QTL results identified from two NAM populations for drought tolerance by October 2020. We will analyze all the data collected from the drought tolerance experiment and complete the data analysis for both goals by November 2020 A final report and a manuscript will be submitted in January 2021.
Impacts
What was accomplished under these goals?
Goal One: Identify quantitative trait loci (QTLs) associated with various processes in hydrotropism: (95% Accomplished) We constructed and tested 10 new units of Hydrotropism Analyzer. The new units were incorporated with many improvements to achieve high durability, easy operation, and greater consistency. The new Analyzers allowed accurate measurement with less variation among the units. The new Hydrotropism Analyzers were used to videotape the hydrotropic response of the two maize Nest Association Mapping (NAM) populations (#11, #18). We have completed the hydrotropic measurement of the two NAM populations which contains more than 250 recombinant inbred lines (RILs). A total of 1,345 recorded videos of these lines were analyzed to obtain all the quantitative data on hydrotropic response in the primary root of maize. Five parameters, including Time for Initiating Bending (IB), Time from Initial Bending to Touching (Tt), Total Time for hydrotropic response (TT), Final Root Angle (FA), and Root Elongation Rate (ER) were used to quantify the hydrotropic process. A total of 109 lines for NAM population #11 and 139 lines for NAM population #18 were used for subsequent QTL analysis. We completed the QTL analysis for both populations based on the hydrotropic phenotyping data collected with our Hydrotropism Analyzers and the genetic maps we constructed using the raw genetic mapping data available in the maize genomic database for the two NAM populations. Permutation tests were used to determine the LOD threshold value of 2.5, and locus with a LOD value greater than the threshold value is considered as a significant QTL. A total of 10 QTL were identified in the #11 NAM population, and the QTL were distributed across maize chromosomes 1, 2, 3, 5, 6, 7, and 8. A total of 19 QTL were identified in the #18 NAM population, and they were distributed across the whole maize genome except for chromosome 6. We discovered 5 QTL on chromosome 2, 5, 7 and 10 that contribute to IB; 5 QTL on chromosome 1, 2 and 3 that affect Tt; 5 QTL on chromosome 1, 2, 3 and 7 that affect TT; 9 QTL on chromosome 1, 2, 3, 5 and 9 that affect FA; 5 QTL on chromosome 4, 6 and 8 that contribute to ER. Most of the QTLs identified are reliable, since the alleles corresponding to stronger hydrotropic response are in accordance with our previous results from the testing of the founder lines of NAM populations in which Hp301 allele (#18) is greater than B73 allele and greater than Oh43 allele (#11). The SNP markers near the QTL peaks were identified, and the B73 reference genome was used to search for the candidate genes (within a centimorgan flanking the QTL) associate with hydrotropic response in the primary root of maize. The candidate genes list is available upon request. The top genes with their possible functions in hydrotropic response will be investigated in the future. Achieving this goal was delayed due to three reasons: 1) The video and image analysis took more time than expected. Each video was examined multiple times to ensure accuracy and consistency of all the data. Thousands of images were analyzed, mostly by manual means, to collect various parameters. 2) Raw genetic mapping data downloaded from the maize genomic database was refined before use for QTL analysis. 3) QTL analysis was done with multiple QTL analysis methods, including single marker analysis, interval mapping, and composite interval mapping, and with multiple statistical analysis software including Excel, RStudio and WinQTL Cartographer as validation. We feel these efforts are necessary and justified since the accuracy of the phenotypic data and genotypic data will directly impact the subsequent QTL analysis. Reliable QTL analysis were the foundation for the downstream drought tolerance experiment, as well as identification and investigation of candidate genes related with hydrotropic response in maize roots. Impact: We produced the first set of QTL related to hydrotropism in a major crop. The QTL and candidate genes identified will be highly valuable for understanding of the genetic and molecular basis of hydrotropic response in maize and other plants. Goal Two: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. (50% Accomplished) We propagated enough seeds needed for the second goal during the summer of 2019. We tried to establish a system that allows one to simultaneously induce hydrotropism and evaluate plant performance in greenhouse conditions. We started with the system proposed in the proposal, in which plants were grown in a large transparent cylindric container so we could visualize the hydrotropic response and evaluate plant growth. The system did not work well, despite significant time and effort invested. The main drawback of the system was that hydro-patterning masked the impact of the hydrotropic response, and thus the difference between the contrast lines. We thus developed a different system that allows separation of hydro-patterning from the hydrotropic response. In this system, young seedlings were grown in square petri dishes containing soil mixture with a pre-established water moisture gradient. In the petri dishes, the soil was divided into 3 zones. The top zone contains a small amount of water-saturated soil into which the young seedlings of maize were transplanted. The limited amount of water-saturated soil provided sufficient water for early development of the young seedlings, but limited the total water supply as the plant grow. The middle zone was the soil with a medium amount of water, and the bottom zone was dry soil. The bottom zone and the middle zone soil were assembled first in the petri dish, and the petri dish was then vertically turned 45 degree before loading the top zone soil. When the primary root grew down through the top zone and the middle zone, the root experienced increasing lower moisture and showed hydrotropism - staying and elongating in the junction area between the middle and the bottom zone (instead of growing into the dry soil in the bottom zone). We were able to reproducibly show hydrotropism in the primary roots of a maize hybrid and the impact on young shoot growth during the tests which typically lasted 2-3 days before the lateral roots started to develop. We are currently conducting additional tests to optimize the system. We are also working on how to quantify the hydrotropic response in this system, since the hydrotropic response in this system shows more dynamical changes and variations. We plan to take both qualitative and quantitative approaches in our analysis to determine which features or parameters in hydrotropic response are most relevant to drought tolerance. Impact: We have developed a simple system to demonstrate hydrotropism in maize primary roots in the soil conditions. The system allows us to rapidly assess hydrotropic response and can be used to determine the significance of hydrotropism in drought tolerance. It may become a valuable tool to screen for drought tolerant genotypes in other crops.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Wang Y, Gu M, Hildreth M, Wu Y. 2019. Spatial expression of genes during hydrotropism in maize roots. Annual Meeting of the South Dakota Academy of Science. April 11-13, Oacoma, SD. (the meeting was canceled due to severe weather)
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Wang Y, Hildreth M, Wu Y. 2019. Spatial expression of genes during hydrotropism in maize roots. Faculty Excellence Day at SDSU. Feb, 18. Brookings, SD.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Tefera H, Kim Y, Wang Y, Auger D, Wu Y. 2019. Discovery of gene for hydrotropic response in maize root. Undergraduate Scholar Day of the Biology Department at SDSU. April, 25. Brookings, SD.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Kim Y, Tefera H, Wang Y, Auger D, Wu Y. 2019. Hydrotropism: discovery of hydrotropic genes through mutations. Undergraduate Scholar Day of the Biology Department at SDSU. April, 25. Brookings, SD.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Wu Y. 2019. Hydrotropism in maize roots. Texas Tech University Department of Biology. Feb, 6. Lubbock, TX.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Wang Y, Afeworki Y, Geng S, Kanchupati P, Gu M, Martins C, Rude B, Tefera H, Kim Y, Ge X, et al. 2020. Hydrotropism in the primary roots of maize. New Phytologist. Feb. 2020
https://doi.org/10.1111/nph.16472.
|
Progress 02/01/18 to 01/31/19
Outputs
Target Audience:International plant and crop research community: I presented a poster (invited) at the Gordon Research Conference in June 2018 on this project. National plant biology research community: we presented a poster at the regional meeting of the American Society of Plant Biologists in March 2018. I also presented a talk at Mississippi State University in Jan 2019 on this project. Undergraduate students: Teaching: I included hydrotropism (our project) in one of the Plant Physiology (BOT 327) lectures in April 2018 and designed class activities to discuss potential mechanisms based on other tropisms that students learned from the class. Students are mostly majoring in Agronomy, Plant Sciences and Horticulture. Research: we trained two undergraduate researchers majoring in Biology in the lab. Both are minority students. They conducted hydrotropism measurement and analyzed the data in the lab. They finished a research proposal and are working on reports. They will present their research in April 2019 during the scholar day on the campus. Graduate students: Teaching: I discussed the research project in the Molecular Plant Physiology class (BIOS/PS664). Research: I recruited and trained a graduate researcher (MS) in June 2018 who is now conducting the research defined in Objective 2 of this proposal. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Postdoctoral researcher Yafang Wang traveled to Iowa State University to present a research poster on this project. MS graduate student Muyu Gu joined the project in June. He participated in redesigning and constructing of our new Hydrotropism Analyzers. He also worked with the PI and Dr. Don Auger, a coPI on the project, in the corn field in the summer to propagate corn seeds needed for this project. He is working with the PI and Dr. Jixiang Wu, another coPI on this project, to optimize root growth and image analysis in the greenhouse. He is currently taking a class from Dr. J Wu (Quantitative Genetics) needed for QTL mapping and analysis in this project. I worked with my undergraduate students, Haileselassie Tefera and Yongjun Kim, on literature reading, proposal development. Lab technical training was provided by graduate students. I will continue to work with them for data analysis and complete the final project report in spring 2019. How have the results been disseminated to communities of interest?We have presented our research project and preliminary data at various conferences. We have also included this research in classroom teaching and prepared a Youtube video for perspective students and their parents and all others who will view the video. What do you plan to do during the next reporting period to accomplish the goals?Goal One: Identify Quantitative Trait Loci (QTLs) associated with various processes in hydrotropism: We will finish hydrotropic measurement of the second NAM population by April 2019. We will complete QTL analysis by August 2019. Goal Two: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. We will compare contrasting lines in their hydrotropic response in a drought stress experiment. We will set up more units for root growth and image analysis using a hybrid genotype from Feb to June. The main purpose to identify a best method to induce hydrotropism in the soil and evaluate its relationship with drought tolerance. We will complete the first experiment to compare the contrast lines identified from two NAM populations for drought tolerance by Nov. 2019 We will complete the 2nd experiment to compare the rest of the contrast lines identified from two NAM populations for drought tolerance by Feb. 2020. A final report and a manuscript will be submitted in March 2020.
Impacts
What was accomplished under these goals?
Goal One: Identify Quantitative Trait Loci (QTLs) associated with various processes in hydrotropism: (30% Accomplished) We constructed and tested 10 new units of the Hydrotropism Analyzer. The new units were incorporated with many improvements to achieve high durance, easy mechanical operation, and greater uniformity among units. This allowed accurate measurement and less variation among the units. We completed the measurement of the first NAM population (#11) which contains more than 100 lines. Currently, we are analyzing the data which will then be used for QTL analysis. This goal was impacted by two reasons that caused some delay: 1) The previous graduate student graduated in May but returned in June to conduct work defined in task 1 listed above, and 2) Construction and calibration of 10 new units of the Hydrotropism Analyzer took more time than we planned. However, we feel this effort was justified since all the downstream analysis and experiments depend on the accuracy of these measurements. Impact: Our new data support our original observation - a significant positive correlation exists between root elongation rate and initiation of hydrotropic bending. This information can potentially impact future breeding for drought tolerant maize. Breeders can screen for genotypes with high sensitivity to moisture gradients simply based on the root elongation rate. Goal Two: Determine whether a stronger hydrotropic response is associated with a greater drought tolerance in maize. (10% Accomplished) In this goal we compare contrasting lines in their hydrotropic response in a drought stress experiment. We developed and tested a system in the greenhouse that allows the visualization and quantification of the number and elongation of roots in the soil. We grew maize plants in clear cylindrical containers (5 feet tall and 8 inch in diameter) and used a camera to take the images of roots. We explored various online tools for image analysis in order to speed up data analysis of the large number of images that we will generate from this project. We are currently experimenting with methods to introduce localized water potential gradients and observe hydrotropism of roots in the soil using a hybrid genotype. Impact: The transparent root growth containers can be a very effective tool to analyze root growth in various conditions. We have tested the effect of locally applied fertilizer on root growth. More roots were found near the locally applied fertilizer. We also observed improved root and plant growth, as well as a reduction in fertilizer application.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Wang Y, Tecleab Y, Kanchupati P, Martin C, Rude B, Auger D, Ge X, Chen S, Yang P, Hu T, Wu Y (2018) Hydrotropic Responses in Maize Primary Roots. Gordon Research Conference, Waterville, NH, June 3-8.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Wang Y, Tecleab Y, Kanchupati P, Martin C, Rude B, Auger D, Ge X, Chen S, Yang P, Hu T, Wu Y (2018) Hydrotropic Responses in Maize Primary Roots ASPB regional meeting, Ames, IA, March 3-4.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Wu Y (2019) Hydrotropism in the primary roots of maize. Mississippi State University, Starkville, MS, January 28.
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