NSF Award
1022017
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. <br/><br/>Broader Impacts. <br/>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.
