P641 ARABIDOPSIS NHR2 MEDIATES VESICLE TRAFFICKING EVENTS DURING PLANT INNATE IMMUNITY Rojas C. M., Lee S. H., Kaundal A., Senthil-Kumar M., Lee H. K., Mysore, K. S. The Samuel Roberts Nobel Foundation Vesicle trafficking mediating the internalization, transport within intracellular compartments and secretion of molecules to the extracellular milieu, has been implicated in processes leading to plant immunity. All these processes involve membrane fusion between vesicles transporting cargo and membrane-bound organelles or the plasma membrane. At the core of these membrane-fusion events is a special class of membrane proteins known as SNARES (soluble N-ethylmaleimide-sensitive factor attachment protein receptor). Both vesicles and target membranes contain SNARES and membrane fusion occurs by the interaction among 4 different SNARES belonging to 4 different families that precedes the transfer of cargo from vesicle to target. Using virus-induced gene silencing (VIGS) in Nicotiana benthamiana to identify genes involved in nonhost disease resistance, we found a plant-specific novel gene that we named NHR2 (nonhost disease resistance 2), and further isolated its homologs in Arabidopsis thaliana: AtNHR2A and AtNHR2B. Transient expression of these genes fused to the green fluorescent protein (GFP) in N. benthamiana revealed that they co-localize with several intracellular compartments. Phylogenetic analysis revealed that AtNHR2A and AtNHR2B are novel uncharacterized SNAREs. AtNHR2B interacts in yeast with EXO70A1 and a Vacuolar Sorting Receptor (VSR), known to function in vesicle trafficking events and the in planta interaction between AtNHR2B and Exo70A1 as well as AtNHR2B and VSR occurs at the plasma membrane. We hypothesize that AtNHR2B mediating the secretion of antimicrobials.
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