OsMYB306-OsRAV11 Regulates Resistance of Rice to Striped Stem Borer by Modulating Serotonin Biosynthesis

Striped stem borer (SSB; Chilo suppressalis Walker) is one of the most destructive pests in rice production. Previous studies have demonstrated that SSB infestation induces transcription of OsT5H (tryptamine-5-hydroxylase) and biosynthesis of serotonin, a newly recognised phytohormone, and that disruption of serotonin biosynthesis significantly increases SSB resistance. However, the regulatory module modulating serotonin biosynthesis remains to be identified and characterised. Here, we reveal an OsMYB306-OsRAV11 module that regulates OsT5H transcription and serotonin biosynthesis in response to SSB infestation in rice. OsMYB306 and OsRAV11 can bind to the OsT5H promoter and repress its transcription. In the module, OsRAV11 interacts with OsMYB306 and enhances its inhibitory effect on OsT5H transcription. CRISPR/Cas9-generated knockout mutants (myb306, rav11 and myb306 rav11) exhibited elevated OsT5H expression, increased serotonin accumulation and reduced SSB resistance. Conversely, OsRAV11 overexpression reduced OsT5H transcription. Our findings establish a transcriptional regulatory framework for the biosynthesis of serotonin in response to SSB infestation. These findings inform the development of new strategies for producing SSB-resistant rice by genome editing, potentially reducing reliance on chemical pesticides for SSB control.