Molecular Mechanism of Plant Response to Wounding: Impact of JA Catabolism

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Plants can perceive tissue damage inflicted by insect feeding, and they rapidly activate several key defense responses. Jasmonate (JA) is the plant hormone that orchestrates these defense responses and dictates an inhibition of growth for plants under stress conditions. JA is also a powerful inducer of many specialized metabolites that have important ecological functions. These metabolites are also a renewable source of many high-value natural products for human use such as nutraceuticals. This project will elucidate how JA levels are precisely regulated to accommodate the various stress adaptive mechanisms of plants. The long term goal of this research is to help reduce or eliminate the need for chemical pesticides and to increase global food production through new approaches to pest control. This research promotes a better understanding of plant defense mechanisms, which can benefit both farmers and horticulturists. This project seeks to improve STEM education by providing multidisciplinary training to college students, graduates and postgraduates. Students from traditionally underrepresented groups in science will be sought through participation in the scientist's institutional outreach programs set up for that purpose. A science literacy program called Sci-LiFT (Science Literacy for Future Teachers) will be developed for students who are in training to become secondary school science teachers. Participating students will engage in real laboratory research on topics relevant to this project and develop a high school teaching module. The Sci-LiFT program is expected to leave an indelible mark on program participants and will positively impact their future teaching in secondary schools. Although the core JA biosynthetic pathway has been delineated, how JA biosynthesis is initiated, maintained, or terminated is unclear. The major scientific goal of this project is to gain a better understanding of the termination of JA signal and to investigate its role in plant responses to wounding. Mutants were isolated that are defective in JA catabolism, and as a result, overaccumulate JA. Highly elevated JA concentration in these mutants was expected to constitutively activate JA-mediated defense responses. Contrary to this expectation, the mutants displayed opposite symptoms, becoming desensitized to JA, thus revealing an important link between JA catabolism and the plant?s long-term responses to stress conditions. This project will use a variety of mutants that are altered in endogenous JA profiles to investigate the dynamic relationship between the relative levels of JA derivatives and plant response to wounding in a well-established Arabidopsis genetic system. The specific aims of this project are: i) to determine the roles of JA turnover and oxidized-JA derivatives in plant response to wounding, ii) to delineate the signaling pathways important for wound response in JA catabolic mutants, and iii) to characterize the function of a new gene identified through a mutant screen for JA catabolism. The proposed project has the potential to identify previously unrecognized regulatory mechanisms of JA signaling and JA-dependent wound responses. This project is also expected to provide new information about how plants prioritize growth versus defense by studying the mutants that appear to defy the growth-defense-tradeoff rule.