Delineating the functional roles of dynamin related proteins in plant innate immunity
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Vesicular trafficking mediates the movement of cargo molecules from donor to target organelles and is emerging as a critical means by which plants modulate immune responses to microbial pathogens. However, relatively few vesicular trafficking proteins have been implicated as regulatory components of plant immune responses. Here, a candidate-based approach was utilized to identify Arabidopsis thaliana Dynamin-Related Protein 2B (DRP2B), as a novel vesicular trafficking protein functioning in flg22-signaling and innate immunity against Pseudomonas syringae. Loss of DRP2B differently affects three distinct branches of the flg22-signaling network. My analysis was extended to investigate other DRP family members which have also been previously implicated in endocytosis. Interestingly, loss of another DRP family member results in an identical separation of immune signaling responses as described for drp2b mutant plants, providing evidence that these two DRPs may operate within a common flg22-induced signaling pathway. In addition to identifying novel components that affect flg22-induced signaling responses, work in this dissertation sought to understand the potential role(s) of flg22-induced endocytosis of FLS2 in the initiation and attenuation of flg22-induced signaling responses. To this end, I made significant contributions showing that vesicular trafficking of FLS2 is important for the desensitization of cells to flg22 via ligand-induced endocytic degradation of FLS2 and that resensitization of cells to flg22 by secretion of newly-synthesized FLS2 prepares cells for subsequent rounds of flg22-perception. Altogether, work in this dissertation provides some of the first evidence of a link between flg22-induced endocytosis of FLS2 and early flg22-signaling responses.
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