A virus-derived small RNA targets the rice transcription factor ROC1 to induce disease-like symptom

Virus-derived small interfering RNAs (vsiRNAs) in plants can target host transcripts to induce symptom development. Southern rice black-streaked dwarf virus (SRBSDV) is the most damaging rice-infecting virus, which causes severe stunting and poorly developed roots in rice plants, thereby posing a serious threat to rice production. In this study, we show that a vsiRNA (vsiR-S9-18), generated from SRBSDV genome segment 9, targets the transcription factor ROC1 in rice. SRBSDV infection triggered the production of vsiR-S9-18 and resulted in the downregulation of ROC1 in rice plants. Transient expression of vsiR-S9-18 in rice protoplasts and tobacco leaves further demonstrated the specific association of vsiR-S9-18 with ROC1 . Moreover, the ROC1 -knockout rice plants displayed shortened roots, similar to the phenotype of root growth inhibition caused by SRBSDV infection. We propose that vsiR-S9-18 inhibits root elongation via ROC1 , which has been proven to regulate root growth. This finding extends our understanding of the role of vsiRNA in viral disease development and is helpful for the development of new antiviral approaches.