Identification of Strawberry Vein Banding Virus Encoded P6 as an RNA Silencing Suppressor

Virology. 2018 Jul;520:103-110. doi: 10.1016/j.virol.2018.05.003. Epub 2018 May 26.

Abstract

RNA silencing is a common mechanism that plays a key role in antiviral defense. To overcome host defense responses, plant viruses encode silencing-suppressor proteins to target one or several key steps in the silencing machinery. Here, we report that the P6 protein encoded by Strawberry vein banding virus (SVBV) is an RNA silencing suppressor through Agrobacterium-mediated co-infiltration assays. SVBV P6 protein can suppress green fluorescent protein (GFP) gene silencing induced by single-stranded RNA but not by double-stranded RNA. The P6 protein can also inhibit systemic silencing of GFP through interfering the systemic spread of GFP silencing signal. Subcellular localization study indicated that P6 protein formed irregular bodies and distributed in both cytoplasm and nucleus of Nicotiana benthamiana cells. Furthermore, deletion analysis indicated that a nuclear localization signal (NLS, aa 402-426) in the P6 protein is responsible for the silencing suppression efficiency. In addition, expression of the P6 protein via a Potato virus X (PVX)-based vectors induced more severe mosaic symptoms in N. benthamiana leaves, and transgenic N. benthamiana plants expressing P6 showed obvious vein yellowing as well as severe mosaic symptoms in leaves. Taken together, our results demonstrates that SVBV P6 is a suppressor of RNA silencing, possibly acting at a upstream step for dsRNA generation.

Keywords: P6 protein; Pathogenicity determinant; RNA silencing suppressor; Strawberry vein banding virus; siRNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agrobacterium / genetics
  • Caulimovirus / genetics*
  • Caulimovirus / metabolism
  • Caulimovirus / pathogenicity
  • Cell Nucleus / virology
  • Cytoplasm / virology
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Gene Silencing
  • Genetic Vectors
  • Green Fluorescent Proteins / genetics
  • Nuclear Localization Signals / genetics
  • Nuclear Localization Signals / metabolism
  • Plant Diseases / virology*
  • Plant Leaves / virology
  • Plant Viruses / genetics
  • Plants, Genetically Modified / virology
  • Potexvirus / genetics
  • RNA / chemistry
  • RNA / genetics
  • RNA Interference*
  • Tobacco / cytology
  • Tobacco / virology
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*

Substances

  • DNA-Binding Proteins
  • Nuclear Localization Signals
  • Viral Proteins
  • viral protein p6
  • Green Fluorescent Proteins
  • RNA

Supplementary concepts

  • Strawberry vein banding virus