Collaborative Research: Function and Regulation of Thimet Oligopeptidase-Mediated Proteolytic Pathways in Plant Stress

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Plants are dynamic living systems in which external and internal signals are integrated to facilitate and sustain growth and health. This research is targeted toward understanding the understudied phenomena of how plants use protein cleavage and degradation in response to stress signals. This knowledge may lead to increased survival rates of crops, and a further understanding of the adaptation and tolerance mechanisms utilized by these crops. A diverse population of graduate, undergraduate and high school students will be trained in modern methods of biochemistry, analytical chemistry, and systems and computational biology. Undergraduates will have the opportunity to participate in a summer exchange Research Experience for Undergraduates (REU) program between Mississippi State University and University of North Carolina at Chapel Hill and the PIs will develop an exhibit with scientific demonstrations for the NC Science Festival targeted to elementary and middle school students. The project employs the plant Arabidopsis as a model to elucidate the contributions of the proteolytic pathways mediated by TOP1 and TOP2 thimet oligopeptidases through integrated biochemical, proteomics, and systems biology approaches. Unique methods have been utilized in the preliminary studies to characterize the interaction of thimet oligopeptidases with the plant stress hormone salicylic acid. Genetic and biochemical experiments uncovered roles for TOPs in pathogen defense as possible "redox sensors". Fundamental differences between TOP1 and TOP2 cellular functions have been revealed experimentally and captured in a cell-level computational model. The research will expand on these findings by addressing the following aspects: (i) characterize redox-specific modifications mediated by and regulating TOP1 and TOP2, (ii) identify the substrate repertoire of TOP1 and TOP2, and (iii) expand and verify predictive models bridging molecular and structural characteristics of TOP1 and TOP2 with the whole-cell response. Upon the successful completion of the proposed research, a framework for TOP signaling in plants will be established and provide critical insights into how the interplay between proteolytic pathways and defense hormone signaling can be harnessed for the benefit of adaptation and tolerance mechanisms of crops.This project is co-funded by the Systems and Synthetic Biology Program in the Division of Molecular and Cellular Biosciences and by the NSF EPSCoR Program.