The Tomato yellow leaf curl virus (TYLCV) is a tomato pathogen that can cause catastrophic yield loss. A central element of plant defence against viruses, including TYLCV, is RNA silencing. Small RNAs (sRNA) triggered by virus infection act as a mobile signal to spread RNA silencing; both the virus itself and the silencing signal move throughout the plant, from cell-to-cell, via plasmodesmata. The C4 protein of TYLCV binds to both RNA and a host plasmodesmal receptor, and has been suggested to facilitate both virus cell-to-cell spread and silencing suppression. This project will combine expertise in plant-virus interactions (Rosa Lozano-Duran, PSC, Shanghai) and plasmodesmata (Christine Faulkner, JIC) to investigate the role of the C4 protein in virus and sRNA movement, with the aim of elucidating mechanisms of virus infection and host defence.