Genetic Analysis of Natural Variation in the Control of Water Use Efficiency and Response to Drought Stress in Brassica rapa

项目负责人：C. Robertson McClung（达特茅斯学院）合作伙伴：Cynthia Weinig和Brent E. Ewers（怀俄明大学），Richard M. Amasino（威斯康辛大学麦迪逊分校）和Todd C. Mockler（俄勒冈州立大学）本项目调查了油菜作物植物水分利用的遗传基础。水分利用效率是农作物产量和野生物种适合度的关键决定因素。植物的内源性昼夜节律与外部非生物条件（包括水分胁迫）之间的匹配可以显著影响叶绿素生成、碳固定和蒸腾水分损失等生理功能。油菜的昼夜节律与蒸腾和水分利用效率之间存在很强的相关性。利用两种亲本基因型中存在的遗传多样性进行的初步研究已经确定了至少十个遗传上确定的影响水利用效率的区域。其中，6个与影响生物钟功能的基因共定位。该项目将克隆A7染色体上一个区域的基因并确定其特征，该区域解释了四分之一以上的水利用效率差异。通过在大气和土壤水平施加水分胁迫的实验，以及植物测量量化水供需之间的联系以及植物的碳固定和利用，将有助于确定潜在的位点。该项目还将描述基因表达对水分胁迫的反应以及一天中的时间对这种反应程度的影响。该项目将开发类似于玉米嵌套关联图谱（NAM）的遗传资源，探索约20个不同亲本的遗传多样性。这将使鉴定出更多有助于提高水利用效率的基因位点成为可能。这些基因又将被精细地绘制和克隆，从而增强我们对作物品种水分利用效率遗传基础的理解。加深对这一作物品种水分利用效率结构的了解，将有助于为提高各种作物品种的水分利用效率而进行育种工作。考虑到作物用水的微小变化对全球水文社会的深远影响，对植物用水和气体交换的遗传控制和自然变化的透彻理解是有必要的，以养活淡水供应日益有限的快速增长的全球人口。该项目为高中、本科、博士前和博士后提供了定量分子和经典遗传分析以及植物生理学的创新教育机会。该项目将培训初中和高中教师，并开发教育模块，允许K-16学生使用快速循环的B. rapa菌株进行经典和分子遗传学的实践研究。威斯康星大学麦迪逊分校的年度暑期学院将提高K-12和本科阶段的经典、分子和生化遗传学教学资源的价值，这些资源已经在课堂上得到了广泛的认可。因此，这个项目的外联方面应在国家一级表现出来。所有数据、生物材料和教学材料将免费通过DIURNAL网站（http://diurnal.cgrb.oregonstate.edu/diurnal_about.html）、公共数据库[NCBI Short Read Archive (SRA) (http://www.ncbi.nlm.nih.gov/Traces/sra/sra.cgi?)]、Gene Expression Omnibus (GEO) （http://www.ncbi.nlm.nih.gov/geo/）、Brassica.info (www.brassica.info)]和/或存储库[拟南芥生物资源中心（ABRC） （http://abrc.osu.edu/）和威斯康星州快速植物计划（WFPP） （http://www.fastplants.org/）])]。

PI: C. Robertson McClung (Dartmouth College)CoPIs: Cynthia Weinig and Brent E. Ewers (University of Wyoming), Richard M. Amasino (University of Wisconsin - Madison), and Todd C. Mockler (Oregon State University)This project investigates the genetic underpinnings of plant water use in the crop species Brassica rapa. Water-use efficiency is a critical determinant of yield in crops and fitness in wild species. The match between a plant's endogenous circadian rhythm and external abiotic conditions, including water stress, can dramatically affect physiological functions such as chlorophyll production, carbon fixation, and water loss through transpiration. Brassica rapa exhibits a strong association between circadian rhythms and both transpiration and water-use efficiency. Preliminary studies exploiting the genetic diversity present in two parental genotypes have identified at least ten genetically defined regions that affect water-use efficiency. Of these, six co-localize with genes affecting circadian clock function. This project will clone and characterize the gene or genes of one region, on Chromosome A7, that explains more than one-quarter of the variation in water-use efficiency. Identifying the underlying locus will be facilitated by experiments where water stress is imposed at the atmospheric and soil levels, and plant measurements quantify the connection between water supply and demand as well as plant carbon fixation and utilization. This project also will characterize the gene expression response to water stress and the influence of time of day on the magnitude of that response. This project will develop genetic resources akin to the maize Nested Association Mapping (NAM) lines that will explore the genetic diversity present in ~20 diverse parents. This should allow the identification of more genetic loci that contribute to water-use efficiency. These in turn will be fine-mapped and cloned, thus enhancing our understanding of the genetic basis of water-use efficiency in crop species. Enhanced understanding of the architecture of water-use efficiency in this crop species should facilitate efforts to breed for enhanced water-use efficiency in a wide range of crop species.Given the profound implications to society of even small changes in crop water use on global hydrology, a thorough understanding of the genetic controls on and natural variation in plant water use and gas exchange is warranted to feed a rapidly growing global population with increasingly limited fresh water supplies. This project offers innovative educational opportunities at the high school, undergraduate, predoctoral and postdoctoral levels in quantitative molecular and classical genetic analysis and plant physiology. The project will train middle and high school teachers and develop educational modules that permit K-16 students to do hands on studies in classical and molecular genetics using a rapid-cycling strain of B. rapa. Annual summer institutes at University of Wisconsin - Madison will enhance the value of a resource to teach classical, molecular, and biochemical genetics at the K-12 and undergraduate levels that has already gained widespread acceptance in the classroom. Thus, the outreach aspects of this project should be manifest on a national level. All data, biological materials, and teaching materials will be freely available through the DIURNAL website (http://diurnal.cgrb.oregonstate.edu/diurnal_about.html), public databases [NCBI Short Read Archive (SRA) (http://www.ncbi.nlm.nih.gov/Traces/sra/sra.cgi?), Gene Expression Omnibus (GEO) (http://www.ncbi.nlm.nih.gov/geo/), Brassica.info (www.brassica.info)] and/or repositories [Arabidopsis Biological Resource Center (ABRC) (http://abrc.osu.edu/) and the Wisconsin Fast Plants Program (WFPP) (http://www.fastplants.org/)].