Minisymposium 8: Cell division

Abs # 21005: Functional analysis of patellin1, a cell-plate localized, phosphoinositide-binding protein

Presenter:	Peterman, Kaye
Authors	Peterman, Kaye  (A)   Le, Elizabeth  (A)   Pierson, Emily  (A)   Schlegel, Lotte  (A)
Affiliations:	(A): Department of Biological Sciences, Wellesley College

Membrane trafficking is central to construction of the cell plate during plant cytokinesis. Consequently, a detailed understanding of the process depends on the characterization of molecules that function in the formation, transport, targeting and fusion of membrane vesicles to the developing plate, as well as those that participate in its consolidation and maturation into a fully functional partition. We report here the initial biochemical and functional characterization of patellin1 (PATL1), a novel cell-plate associated protein that is related in sequence to proteins involved in membrane trafficking in other eukaryotes. PATL1 is one of a small family of Arabidopsis proteins, characterized by a variable N-terminal domain followed by two domains found in other membrane trafficking proteins (Sec14 and GOLD domains). Immunolocalization and biochemical fractionation studies suggest that PATL1 is recruited from the cytoplasm to the expanding and maturing cell plate. In vesicle binding assays, PATL1 binds to specific phosphoinositides, important regulators of membrane trafficking, with a preference for PtdIns(5)P, PtdIns(4,5)P₂and PtdIns(3)P. Taken together these findings suggest a role for PATL1 in membrane trafficking events associated with cell plate expansion or maturation and point to the involvement of phosphoinositides in cell plate biogenesis. Several approaches are being taken to dissect the biological function of the PATLs. A yeast two-hybrid screen is underway to identify proteins that interact with PATL1 and PATL2. Their N-terminal domains contain several predicted protein-protein interaction sites including a coiled-coil and proline-rich motifs. GOLD domains are typically involved in protein-protein interactions as well. Several putative interactors have been identified thus far and one of these interferes with cytokinesis in yeast. Analysis of T-DNA insertion mutants is also underway to determine if the PATLs play an essential role in cytokinesis. Several independent T-DNA insertions, in both the PATL1 and PATL2 genes, have been identified by PCR genotyping. Results from the phenotypic analysis of these mutants will be presented. Identification of binding partners and the characterization of knockout mutants will provide insight into PATL1’s role at the cell plate.