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的积累增加。特别是，在拟南芥和其他植物物种中，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。这种大的动态范围内的支链氨基酸积累提供了一个可靠的和定量的分析，调查的监管网络，导致植物在渗透胁迫过程中的代谢变化。敲除突变的15个测试的转录因子中的4个表明，他们有缺陷的干旱诱导，但不是基础水平的异亮氨酸，亮氨酸和缬氨酸。虽然这些基因中的一些先前已被研究的其他原因，没有一个已经与以前的调节支链氨基酸的生物合成。进一步的拟南芥基因表达和代谢途径的生物信息学分析将确定额外的转录因子，调节支链氨基酸的生物合成。转录因子敲除和过表达株系的测定将有助于确定这些单个基因在植物适应渗透胁迫期间所作的贡献。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。异亮氨酸、亮氨酸和缬氨酸的生物合成大量增加，这将在拟南芥中进行研究，在受到渗透胁迫的作物中也观察到了这一点。因此，这些拟南芥反应的研究将导致确定的基本调控途径，可能有助于作物耐旱性和耐盐性的发展。异亮氨酸也被认为是世界上一些主要粮食作物中的限制性必需氨基酸。调节异亮氨酸生物合成途径的转录因子可以靶向方式实施以增加水稻、马铃薯或其他农业相关植物物种中的异亮氨酸积累。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.