The circadian clock component OsRVE6a orchestrates daytime SA-JA signaling crosstalk to enhance rice defenses.

Abstract

Salicylic acid (SA) and jasmonic acid (JA) are key plant defense hormones that typically exhibit antagonistic interactions, with JA levels peaking during the day and SA at night. However, how plants sustain SA-mediated immunity during daylight when JA defenses dominate remains unclear. Here, we identify the rice oscillator gene OsRVE6aas a central regulator enabling simultaneous activation of SA and JA pathways during daytime biotic stresses. Daytime feeding by the small brown planthopper (SBPH) induces OsRVE6a expression and alters circadian rhythms in rice. OsRVE6a maintains phased JA and SA peaks, activates JA signaling via the receptor OsCOI1a to align JA signaling with JA content peaks, and alleviates their antagonism by suppressing OsNPR1. Concurrently, OsRVE6a directly activates OsNPR1-responsive defense genes such as OsWRKY20 and OsPR1 ensuring SA-responsive gene expression despite OsNPR1 reduction. Genetic analysis confirms that OsWRKY20 is essential for OsRVE6a-mediated SBPH resistance. These findings establish OsRVE6a as a molecular orchestrator linking circadian timing and immune coordination, enhancing rice resilience to biotic stresses.