Over 40% of the world's food supply is lost to damage caused by pathogens, pests and weeds. Therefore, novel strategies to enhance plant productivity and resistance to pests will significantly increase the security of the world's food supply. To achieve this goal, a deep understanding the mechanisms that control resistance to insects is needed. This project is at the cutting edge of plant-insect interactions and will reveal how chloroplasts communicate with nuclei to coordinate a robust defense after injury and insect attack; this knowledge will enable new strategies for insect resistance in the future. This project is a fertile training ground for a graduate student. Graduate student leadership skills will be developed through guiding undergraduate's in this project. UCR is a minority-serving institution and this project will recruit and engage students with diverse backgrounds. Results from the project will be disseminated by publications in scientific journals, lay talks to Riverside K-12 schools and the public, and talks at meetings and universities.
This project will study the importance of a tomato chloroplast-localized protein called leucine aminopeptidase (LAP-A) and its role in generating a signal that controls nuclear gene expression after insect feeding and wounding. This project will identify the LAP-A-dependent signal that mediates this chloroplast-to-nucleus communication. The protein/peptide (target) that LAP-A acts on will be identified and the target may be the signal or may create the signal. LAP-A has two activities. LAP-A is an aminopeptidase and may produce the signal by modifying the N-terminus of a target protein/peptide that resides in the chloroplast. LAP-A is also a molecular chaperone and may help targets stay in an active folded state. These activities should influence the target's structure, activity and/or stability and thereby signal production. This project will use cutting-edge proteomics technologies to measure proteins/peptides in three tomato lines that express different levels of LAP-A (LapA-silenced, LapA-overexpressing, and wild type). Aim 1 will identify chloroplast proteins that are (1) cut by LAP-A and (2) have altered stability that is strictly correlated with the presence/absence of LAP-A. Aim 2 will determine the LAP-A-dependent changes in a small peptide called glutathione (GSH). Preliminary data link LAP-A and GSH turnover. GSH is an excellent candidate for the signal as it regulates two defense signals (reactive oxygen species and redox status) in other systems. The identity of LAP-A's targets will reveal the nature of the LAP-A-generated signal that mediates chloroplast-nucleus communication.