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

SUMMARY 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.