Non-structural protein P6 encoded by rice black-streaked dwarf virus is recruited to viral inclusion bodies by binding to the viroplasm matrix protein P9-1

Abstract

Like other members of the family Reoviridae, rice black-streaked dwarf virus (RBSDV, genus Fijivirus) is thought to replicate and assemble within cytoplasmic viral inclusion bodies, commonly called viroplasms. RBSDV P9-1 is the key protein for the formation of viroplasms, but little is known about the other proteins of the viroplasm or the molecular interactions amongst its components. RBSDV non-structural proteins were screened for their association with P9-1 using a co-immunoprecipitation assay. Only P6 was found to directly interact with P9-1, an interaction that was confirmed by bimolecular fluorescence complementation assay in Spodoptera frugiperda (Sf9) cells. Immunoelectron microscopy showed that P6 and P9-1 co-localized in electron-dense inclusion bodies, indicating that P6 is a constituent of the viroplasm. In addition, non-structural protein P5 also localized to viroplasms and interacted with P6. In Sf9 cells, P6 was diffusely distributed throughout the cytoplasm when expressed alone, but localized to inclusions when coexpressed with P9-1, suggesting that P6 is recruited to viral inclusion bodies by binding to P9-1. P5 localized to the inclusions formed by P9-1 when co-expressed with P6 but did not when P6 was absent, suggesting that P5 is recruited to viroplasms by binding to P6. This study provides a model by which viral non-structural proteins are recruited to RBSDV viroplasms.

Label-Free Quantitative Proteomic Analysis of Chitosan Oligosaccharide-Treated Rice Infected with Southern Rice Black-Streaked Dwarf Virus

“…After COS processing, we identified some defense-related proteins, simultaneously the expression of SRBSDV P9-1 and P5 protein were down-regulated [42,43]. Previous studies have shown that the interaction between P9-1 and P5 were essential proteins that formed viroplasms [44,45]. Our results indicated that COS may decrease the infection ability of SRBSDV.…”

Rice Reoviruses in Insect Vectors

“…These viroplasm matrix proteins can act as the targets for antiviral molecule screening (106). Other viral nonstructural and structural components are then recruited to viroplasm matrices for genome replication and progeny virion assembly (18,19,46,61,68,99,105). Currently, whether the insect components are involved in the formation of viroplasms is unknown.…”

Abscisic acid negatively modulates plant defence against rice black‐streaked dwarf virus infection by suppressing the jasmonate pathway and regulating reactive oxygen species levels in rice

“…The functions of only a few of these viral proteins have been studied. P5‐1, P6, and P9‐1 proteins together constitute the viroplasm inclusion (Akita et al, ; L. Sun, Xie, Andika, Tan, & Chen, ; Q. Wang et al, ), which is the site of viral replication and assembly. S7‐1 encodes a tubular protein and is localized in the PD of plant cells (Isogai, Uyeda, & Lee, ; Z.…”

“…P5-1, P6, and P9-1 proteins together constitute the viroplasm inclusion (Akita et al, 2012;L. Sun, Xie, Andika, Tan, & Chen, 2013;Q.…”