Arabidopsis SYNAPTOTAGMIN A plays a key role in membrane contact sites formation, virus movement and plasmodesmata regulation.
A. LEVY (1), S. Lazarowitz (2) (1) University of Florida, U.S.A.; (2) Cornell University, U.S.A.

Membrane contact sites (MCS) are regions where two opposed organelles come to a very close distance of 10-30 nm, which enables a direct transfer of small molecules, thus providing a route for non-vesicular communication between organelles. MCSs play an important role in intracellular signaling and organelle trafficking in eukaryotic cells, but the components and functions of these sites in plants are starting to be understood. Recently we were one of two labs that showed Arabidopsis SYNAPTOTAGMIN A (SYTA), a key regulator of plants biotic stress and virus intercellular movement, localizes to ER-PM contact sites. To understand how SYTA can help virus cell-to-cell spread, we have examined the interaction of SYTA with the Turnip vein clearing virus movement protein (MPTVCV) in infected cells. Our studies show that SYTA directly interacts with MPTVCV at virus replication sites, and that intracellular trafficking of MPTVCV to plasmodesmata (PD) is inhibited in the Arabidopsis SYTA knockdown line syta-1. In addition, the accumulation of stress-induced callose at PD is also inhibited in the syta-1 line. In contrast to these findings, the accumulation in PD of the integral membrane protein PDLP1, which traffics through the secretory pathway to reach PD, is not inhibited in syta-1. Thus, SYTA is required for MPTVCV to traffic to PD by a pathway that is distinct from the secretory pathway. We propose that the diverse movement proteins encoded by Begomoviruses, Tobamoviruses and Potyviruses bind to and hijack SYTA to traffic to plasmodesmata via MCSs. Our results also suggest that this SYTA-mediated trafficking pathway has an additional role in inducing callose deposition at PD during plant responses to stress.

Abstract Number: P7-182
Session Type: Poster