Structural and Functional Study of Protein Post-Translational Modifications involved in Plant Stress Signaling

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Abiotic stresses, such as drought, flood, salinity or extreme temperatures, can severely reduce the yield of major agricultural crops, and these losses are increasing as the effects of climate change become more pronounced. Plants respond to abiotic stresses at the molecular level by triggering signaling pathways that lead to changes in the expression of numerous genes to allow plants to acclimate to their new environment. Ubiquitination and SUMOylation, two post-translational modifications where Ubiquitin or SUMO (Small Ubiquitin-like Modifier) proteins are covalently attached to target proteins, are increasingly recognized as playing a prominent role in the modulation of these pathways. However, how they operate at the molecular level remains quite elusive. The overarching goal of my research program is to structurally and functionally characterize the molecular determinants of Ubiquitination and SUMOylation events involved in plant response to abiotic stresses so that better stress-resilient plant mutants can be rationally designed or selected. Towards this goal, the three following specific objectives will be addressed: 1. Identify the molecular determinants of specific and validated SUMOylation events involved in plant abiotic stress response. 2. Determine how plants balance growth and stress responses at the molecular level by characterizing specific post-translational modification events in the signaling pathway of gibberellins, a family of plant growth regulators that are also involved in plant stress response. 3. Understand the contribution of selected individual and collective E3-substrate interactions to plant abiotic stress response through functional analyses in the model organism Arabidopsis thaliana. In doing so, our research program will generate a framework for understanding interactions involved in plant stress response at the molecular level, with a special interest for post-translational modifications, as these can rapidly remodel entire response pathways. This should facilitate the design or selection of plants with increased tolerance to abiotic stress. Mutants of the gibberellin and SUMOylation pathways are already attractive targets for crop improvement. Our gained structural information will further allow genetic engineering of agronomically useful plants in a very targeted and tunable manner. Also, the identification of the molecular determinants and their validated role in stress response, will help predict the effects of natural variations in genomic populations. Such variants could then be isolated through marker-assisted breeding strategies and would constitute an alternative to the commercial development of transgenic plants. Our research program should thus provide important benefits to Canadian agriculture in a context where pressure on global agriculture steadily increases with increasing world population, shrinking agricultural area, and significant climate change.