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多种生理变化，包括所有组织类型中游离氨基酸积累的增加。特别是，支链氨基酸（异亮氨酸、亮氨酸和缬氨酸）的丰度在拟南芥和其他植物物种中可以增加100倍或更多。支链氨基酸积累的大动态范围为研究渗透胁迫下植物代谢变化的调控网络提供了可靠的定量分析方法。在15个被测试的转录因子中，有4个基因敲除突变表明它们在干旱诱导下有缺陷，但在异亮氨酸、亮氨酸和缬氨酸的基础水平上没有缺陷。虽然这些基因中的一些已经因为其他原因被研究过，但它们都没有与调节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。利用转录因子敲除和过表达系进行检测，将有助于确定这些基因在植物适应渗透胁迫过程中所起的作用。更广泛的影响。非生物胁迫，特别是干旱和盐胁迫，极大地限制了世界许多地区的农业生产力。将在拟南芥中研究的异亮氨酸、亮氨酸和缬氨酸的生物合成的大量增加，也已在遭受渗透胁迫的作物植物中观察到。因此，对这些拟南芥反应的研究将有助于确定基本的调控途径，从而有助于作物植物的耐旱性和耐盐性的发展。异亮氨酸在世界上一些主要粮食作物中也被认为是一种限制性必需氨基酸。调控异亮氨酸生物合成途径的转录因子可以有针对性地增加水稻、土豆或其他农业相关植物物种的异亮氨酸积累。该项目将有助于培养新一代生物信息学和植物代谢生物化学的研究生和本科生。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/）一个完善的教育和推广计划招募。此外，主要研究人员将参与教学，无论是在大学课堂设置和正在进行的推广工作，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.