p2 of rice stripe virus (RSV) interacts with OsSGS3 and is a silencing suppressor.

A rice cDNA library was screened by a galactosidase 4 (Gal4)-based yeast two-hybrid system with Rice stripe virus (RSV) p2 as bait. The results revealed that RSV p2 interacted with a rice protein exhibiting a high degree of identity with Arabidopsis thaliana suppressor of gene silencing 3 (AtSGS3). The interaction was confirmed by bimolecular fluorescence complementation assay. SGS3 has been shown to be involved in sense transgene-induced RNA silencing and in the biogenesis of trans-acting small interfering RNAs (ta-siRNAs), possibly functioning as a cofactor of RNA-dependent RNA polymerase 6 (RDR6). Given the intimate relationships between virus and RNA silencing, further experiments were conducted to show that p2 was a silencing suppressor. In addition, p2 enhanced the accumulation and pathogenicity of Potato virus X in Nicotiana benthamiana. Five genes that have been demonstrated to be targets of TAS3-derived ta-siRNAs were up-regulated in RSV-infected rice. The implications of these findings are discussed.