Journal Article

Barley stripe mosaic virus infection requires PKA-mediated phosphorylation of γb for suppression of both RNA silencing and the host cell death response

Xianbing Wang, Xuan Zhang, Kun Zhang, Dawei Li, Kai Dong, Chenggui Han, Kai Xu, Jialin Yu, Meng Yang, Xuejiao Jin, Yongliang Zhang

2018

Overview

The Barley stripe mosaic virus (BSMV) γb protein is a viral suppressor of RNA silencing (VSR) and symptom determinant. However, it is unclear how post-translational modification affects the different functions of cb. Here, we demonstrate that γb is phosphorylated at Ser-96 by a PKA-like kinase in vivo and in vitro. Mutant viruses containing a nonphosphorylatable substitution (BSMVS96A or BSMVS96R) exhibited reduced viral accumulation in Nicotiana benthamiana due to transient induction of the cell death response that constrained the virus to necrotic areas. By contrast, a BSMVS96D mutant virus that mimics γb phosphorylation spread similarly to the wild-type virus. Furthermore, the S96A mutant had reduced local and systemic γb VSR activity due to having compromised its binding activity to 21-bp dsRNA. However, overexpression of other VSRs in trans or in cis failed to rescue the necrosis induced by BSMVS96A, demonstrating that suppression of cell death by γb phosphorylation is functionally distinct from its RNA silencing suppressor activities. These results provide new insights into the function of γb phosphorylation in regulating RNA silencing and the BSMV-induced host cell death response, and contribute to our understanding of how the virus optimizes the balance between viral replication and virus survival in the host plants during virus infection.

• Publisher: New Phytologist Trust,Wiley Subscription Services, Inc
• Subject: Amino Acid Sequence / Apoptosis / Barley / Barley stripe mosaic virus / Barley stripe mosaic virus (BSMV) / Cell Death / Cyclic AMP-Dependent Protein Kinases - metabolism / Double-stranded RNA / host cell death response / Host plants / Host-Pathogen Interactions / Mortality / mutants / Mutation - genetics / Necrosis / Nicotiana - cytology / Nicotiana - virology / Nicotiana benthamiana / Nucleic acids / Phenotype / Phosphorylation / Phosphoserine - metabolism / PKA / Plant Diseases - virology / Plant Leaves - virology / Plant virus diseases / Plant viruses / Plant Viruses - pathogenicity / post-translational modification / Protein kinase A / Proteins / Ribonucleic acid / RNA / RNA Interference / RNA silencing / RNA-mediated interference / suppression / Viral Proteins - chemistry / Viral Proteins - metabolism / Viral replication / Virus Replication / Viruses / γb protein