Studies On The Interaction Between Arabidopsis RAB2 And VPS34

PI3K(AtVPS34) in Arbidopsis is a phosphatidylinositol 3-kinase, It can produce PI3P from PtdIns, PI3P plays important roles in many processes, such as the maintenance of cell polarity, intracellular trafficking of vesicles, proper location of proteins. AtRAB2 is a small protein that can bind to GTP, It can cycle between the active GTP-bound form and the inactive GDP-bound form, regulate different biological processes with its effectors. We screened AtVPS34 interaction protein AtRAB2 by means of yeast library screening. In order to determine the relationship between the AtRAB2 and AtVPS34, we verify the interaction between AtRAB2 and each domain of AtVPS34 by means of yeast two hybrid (Y2H), Bimolecular fluorescence complementation (BiFC) and Pull-Down. The results show that AtRAB2 interacts with the PIK domain of AtVPS34, which is a hinge region and its role is unclear. AtVPS34 locates in the downstream of AtRAB2. AtRAB2-RNAi displays auxin defect phenotypes similar to AtVPS34-RNAi, such as primary roots short, rosette leaves small and growth dwarfed. Localization of auxin transport protein PIN2 and the auxin responsive element DR5 were partially abnormal, suggesting that AtRAB2 may regulate plant organ development and morphogenesis by mediating auxin transport. In order to determine AtRAB2 regulatory mechanism of plant growth and development, we observe PIN2 location in AtRAB2-RNAi after BFA and FM4-64 treatments. The polar position of PIN2 in the PM is associated with the dynamic balance between the degradation in vacuole and recycling to PM. Most of PIN2 protein recycling to PM depends on GNOM pathway. BFA is the inhibitor of GNOM complex and FM4-64 is a marker of endocytosis that can mark the degradation of PIN2 protein to vacuole. The results shows that PIN2 protein localization is not affected, suggesting that AtRAB2 don’t participate in endocytosis and GNOM-dependent pathways. AtRAB2 may participate in other protein transportation pathway to regulate polar position of auxin efflux transporter and polar distribution of auxin, and regulate plant growth and development.