Oscillator Gene OsRVE6a Coordinates Multi-Level Defense Mechanisms against Small Brown Planthopper in Rice

Pest and disease outbreaks are considerable threats to global food security. Salicylic acid (SA) and jasmonic acid (JA) are key defense hormones that play crucial roles in plant resistance to biotic stresses. However, the mechanism by which the circadian clock orchestrates JA and SA synthesis and signaling at different times of the day to reduce antagonism remains unclear. In this study, we demonstrated that small brown planthopper (SBPH, Laodelphax striatellus , Fallén) infestation acts as a circadian input that not only induced oscillator gene REVEILLE6a ( OsRVE6a ) expression in rice leading to enhanced resistance to SBPH infestation but also altered the circadian rhythm. Additionally, OsRVE6a increased peak levels of JA during the day and SA at night. At peak JA concentration, OsRVE6a activated the JA receptor OsCOI1a and suppressed the activation of the SA master regulator OsNPR1 , thereby alleviating the antagonistic crosstalk between SA and JA pathways and synchronizing JA content with the active phase of JA signaling. Moreover, OsRVE6a directly activated the defense gene OsWRKY20 , compensating for reduced activation by OsNPR1 . Molecular analyses confirmed that OsWRKY20 was essential for OsRVE6a -mediated resistance to SBPH infestation in rice. Our findings suggest that OsRVE6a acts as a molecular orchestrator that links the circadian clock to rice responses to biotic stresses, coordinating various defense mechanisms to enhance rice resistance to SBPH.