Palmitoylation of γb protein directs a dynamic switch between Barley stripe mosaic virus replication and movement

Abstract

Viral replication and movement are intimately linked; however, the molecular mechanisms regulating the transition between replication and subsequent movement remain largely unknown. We previously demonstrated that the Barley stripe mosaic virus (BSMV) γb protein promotes viral replication and movement by interacting with the αa replicase and TGB1 movement proteins. Here, we found that γb is palmitoylated at Cys‐10, Cys‐19, and Cys‐60 in Nicotiana benthamiana , which supports BSMV infection. Intriguingly, non‐palmitoylated γb is anchored to chloroplast replication sites and enhances BSMV replication, whereas palmitoylated γb protein recruits TGB1 to the chloroplasts and forms viral replication‐movement intermediate complexes. At the late stages of replication, γb interacts with NbPAT15 and NbPAT21 and is palmitoylated at the chloroplast periphery, thereby shifting viral replication to intracellular and intercellular movement. We also show that palmitoylated γb promotes virus cell‐to‐cell movement by interacting with NbREM1 to inhibit callose deposition at the plasmodesmata. Altogether, our experiments reveal a model whereby palmitoylation of γb directs a dynamic switch between BSMV replication and movement events during infection. image Viral replication and subsequent intercellular movement are two critical steps for efficient plant infection. This work reveals induction of a replication‐to‐movement switch by palmitoylation of the viral γb protein during Barley stripe mosaic virus (BSMV) infection. Non‐palmitoylated γb is anchored to the chloroplasts and promotes BSMV replication. During the late stages of replication, S‐acyltransferases NbPAT15 and NbPAT21 palmitoylate γb at the periphery of chloroplasts. Palmitoylated γb recruits the TGB1 movement protein to chloroplasts, thereby inducing a shift between viral replication and movement phases. Palmitoylated γb promotes viral cell‐to‐cell movement by inhibiting NbREM1‐dependent callose deposition at plasmodesmata.