P-254 - Plasmodesmal-associated receptor-like kinase RDA2 recognizes tobacco mosaic virus movement protein

Cell-to-cell movement is essential for the spread of plants viruses during infection. To facilitate this process, plant viruses exploit plasmodesmata (PD)—intercelular channels that facilitates molecular exchange—by employing movement proteins (MPs) that mediate the transport of viral genomes through interactions with host factors. While several host components involved in viral movement have been identified, the mechanisms governing MP recognition of PD and the regulation of transport remain poorly understood. Here, we used TurboID-based proximity labeling to define the network of proteins in the vicinity of the MP of tobacco mosaic virus (TMV). Among the 113 MP-proximal proteins identified, we found that the Arabidopsis receptor-like kinase RESISTANT TO DPFM-INHIBITION OF ABSCISIC ACID SIGNALING 2 (RDA2) associates with TMV MP. Fluorescence microscopy revealed that RDA2 localizes to both the plasma membrane and PD and interacts with MP via its kinase domain. Furthermore, in vitro phosphorylation assays showed that RDA2 phosphorylates TMV MP at previously uncharacterized residues, suggesting a potential regulatory role in viral movement. Our findings provide new insights into the host factors influencing viral transport and raise the possibility that receptor-like kinases contribute to the regulation of MP function. Further investigation will determine the biological significance of RDA2-dependent MP phosphorylation in TMV infection.