Rice CIRCADIAN CLOCK ASSOCIATED 1 Transcriptionally Regulates ABA Signaling to Confer Multiple Abiotic Stress Tolerance

The circadian clock facilitates the survival and reproduction of crop plants under harsh environmental conditions such as drought and osmotic and salinity stresses, mainly by reprogramming the endogenous transcriptional landscape. Nevertheless, the genome-wide roles of core clock components in rice (Oryza sativa L.) abiotic stress tolerance are largely uncharacterized. Here, we report that CIRCADIAN CLOCK ASSOCIATED1 (OsCCA1), a vital clock component in rice, is required for tolerance to salinity, osmotic, and drought stresses. DNA affinity purification sequencing coupled with transcriptome analysis identified 692 direct transcriptional target genes of OsCCA1. Among them, the genes involved in abscisic acid (ABA) signaling, including group A protein phosphatase 2C genes and basic region and leucine zipper 46 (OsbZIP46), were substantially enriched. Moreover, OsCCA1 could directly bind the promoters of OsPP108 and OsbZIP46 to activate their expression. Consistently, oscca1 null mutants generated via genome editing displayed enhanced sensitivities to ABA signaling. Together, our findings illustrate that OsCCA1 confers multiple abiotic stress tolerance likely by orchestrating ABA signaling, which links the circadian clock with ABA signaling in rice.