JA-responsive R2R3-type MYB transcription factor OsMYB4P confers broad-spectrum antiviral immunity in rice

Jasmonic acid (JA) plays a critical role in antiviral defence in rice, where viral infection activates JA signalling by degrading Jasmonate ZIM domain (JAZ) proteins, thereby releasing transcription factors (TFs) to drive JA-mediated defence gene expression. While the JA-responsive TF OsMYC2 has been extensively studied in rice, the involvement of MYB TFs in JA signalling remains largely unexplored. In this study, we identified a novel JA-responsive R2R3-type MYB TF OsMYB4P. OsMYB4P functions as a transcriptional activator, activating the expression of the JA synthesis gene CM-LOX1, and positively regulating rice sensitivity to JA. Additionally, OsMYB4P interacts with OsJAZs and is subject to transcriptional inhibition by OsJAZs. Overexpression of OsMYB4P (OE-OsMYB4P) enhances rice resistance to viral infection, whereas knockout mutants (osmyb4p) exhibit increased susceptibility. Further studies revealed that viral proteins SP8 and P2, encoded by southern rice black-streaked dwarf virus (SRBSDV) and rice stripe virus (RSV), respectively, disrupt OsMYB4P self-interaction. This interference reduces OsMYB4P protein stability, transcriptional activation and DNA binding ability, thereby suppressing JA signalling and facilitating the viral infection. Overall, our findings demonstrate that the JA-responsive R2R3-type MYB TF OsMYB4P, as a direct target of JAZs, plays a key role in JA signalling and contributes to broad-spectrum antiviral defence in rice.