Arabidopsis 2010: Regulation of Branched-Chain Amino Acid Biosynthesis, a Paradigm for Studying Osmotic Stress Responses

植物对干旱和盐胁迫的反应是通过各种生理变化，包括所有组织类型中游离氨基酸的积累增加。特别是，在拟南芥和其他植物中，支链氨基酸(异亮氨酸、亮氨酸和缬氨酸)的丰度可以增加100倍或更多。这种大的支链氨基酸积累的动态范围为研究渗透胁迫下导致植物代谢变化的调控网络提供了可靠的定量检测方法。在被测试的15个转录因子中，有4个的敲除突变表明，它们在干旱诱导的转录因子中存在缺陷，但不存在异亮氨酸、亮氨酸和缬氨酸的基础水平。尽管这些基因中的一些已经因为其他原因而被研究过，但它们中没有一个与调控支链氨基酸的生物合成有关。对拟南芥基因表达和代谢途径的进一步生物信息学分析将确定调节支链氨基酸生物合成的其他转录因子。对转录因子敲除和过表达品系的分析将有助于确定这些单个基因在植物适应渗透胁迫过程中的贡献。更广泛的影响。非生物胁迫，特别是干旱和盐分，极大地限制了世界许多地区的农业生产力。在受渗透胁迫的作物中，异亮氨酸、亮氨酸和缬氨酸的生物合成也被观察到大幅增加，这将在拟南芥中进行研究。因此，对拟南芥这些反应的研究将有助于识别可能有助于作物耐旱耐盐发展的基本调控途径。异亮氨酸也被认为是世界上一些主要粮食作物的限制性必需氨基酸。调控异亮氨酸生物合成途径的转录因子可以有针对性地实施，以增加异亮氨酸在水稻、土豆或其他农业相关植物中的积累。该项目将有助于培养生物信息学和植物代谢生物化学方面的新一代研究生和本科生。参与该项目的本科生暑期实习生将通过博伊斯·汤普森研究所(http://www.bti.cornell.edu/pgrp/).)完善的教育和外展计划招募此外，首席调查人员将参与教学，包括大学课堂环境和正在进行的外展工作，以教育社区成员有关植物生物化学、生物信息学和分子生物学。

Plants respond to drought and salt stress with a variety of physiological changes, including elevated accumulation of free amino acids in all tissue types. In particular, the abundance of branched-chain amino acids (isoleucine, leucine, and valine) can increase 100-fold or more in Arabidopsis and other plant species. This large dynamic range in branched-chain amino acid accumulation provides a reliable and quantitative assay for investigating the regulatory networks that lead to metabolic changes in plants during osmotic stress. Knockout mutations in four out of fifteen tested transcription factors showed that they have defects in drought-induced, but not basal levels of isoleucine, leucine, and valine. Although some of these genes have been studied previously for other reasons, none of them have been associated previously with regulating branched-chain amino acid biosynthesis. Further bioinformatic analysis of Arabidopsis gene expression and metabolic pathways will identify additional transcription factors that regulate branched-chain amino acid biosynthesis. Assays with transcription factor knockout and overexpression lines will help to determine the contributions that these individual genes make during plant adaptation to osmotic stress. Broader Impacts. Abiotic stress, in particular drought and salt, greatly limit agricultural productivity in many parts of the world. Large increases in the biosynthesis of isoleucine, leucine, and valine, which will be studied in Arabidopsis, have also been observed in crop plants subjected to osmotic stress. Therefore, research on these Arabidopsis responses will lead to the identification of basic regulatory pathways that may aid in the development of drought and salt tolerance in crop plants. Isoleucine is also considered a limiting essential amino acid in some of the world's major food crops. Transcription factors that regulate the isoleucine biosynthesis pathway may be implemented in a targeted manner to increase isoleucine accumulation in rice, potatoes, or other agriculturally relevant plant species. This project will contribute to training a new generation of graduate and undergraduate students in bioinformatics and plant metabolic biochemistry. Undergraduate summer interns participating in the project will be recruited through a well-established education and outreach program at the Boyce Thompson Institute (http://www.bti.cornell.edu/pgrp/). Additionally, the principal investigators will be involved in teaching, both in a university classroom setting and in ongoing outreach efforts to educate community members about plant biochemistry, bioinformatics, and molecular biology.