graduate student University of Vermount South Burlington, Vermont
Body of Abstract: SNAREs (Soluble NSF Attached Receptors) are essential for endosomal trafficking pathways by mediating vesicle fusion between compartments. VTI13 is a member of the VTI family of SNARES in Arabidopsis that localizes to early endosomes and the tonoplast membrane. Genetic analysis showed that vti13 mutants are defective in polarized root hair growth and root epidermal cell wall organization. To identify proteins that are trafficked to the vacuole using a VTI13-dependent pathway, we used a proteomic approach with transgenic lines expressing GFP-VTI13. These experiments identified several plasma membrane proteins that are potential cargo of VTI13 early endosomes including Patellin 1 (PATL1), Arabidopsis Proton ATPase (AHA)1 and AHA2. AHA1 and AHA2 are the major proton ATPases functioning in root epidermal cells where they act in maintaining a pH gradient necessary for cell expansion. Patellin 1 localizes to the cell plate, associates with phosphatidylinositols in the plasma membrane, and likely functions in diverse aspects of plant growth. I have generated transgenic plants expressing RFP fusions for PATL1, AHA1, and AHA2 that I will cross with GFP-VTI13 expressing lines. We will use F1 seedlings from these crosses to 1) investigate whether PATL1, AHA1, and AHA2 colocalize with GFP-VTI13 in early endosomes and 2) whether they are trafficked to the vacuole in Arabidopsis seedlings. In addition, we are using a genetic approach to identify whether the endosomal trafficking pathway used by VTI13 to traffic cargo to the lytic vacuole is RAB-dependent or RAB-independent in root epidermal cells.