The pre-mRNA splicing factor ZOP1 contributes to the regulation of plant immunity

The Arabidopsis (Arabidopsis thaliana) receptor-like protein SUPPRESSOR OF NPR1-1, CONSTITUTIVE 2 (SNC2) confers basal resistance against pathogens. The transcription factor CALMODULIN-BINDING PROTEIN 60g (CBP60g) and its homolog SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) define two parallel pathways downstream of SNC2. Here, we report the identification and characterization of ZINC-FINGER AND OCRE DOMAIN-CONTAINING PROTEIN 1 (ZOP1), a pre-mRNA splicing factor that functions as a positive regulator of SNC2-mediated immunity. ZOP1 functions immediately downstream of SNC2 before the defense signals branch to CBP60g and SARD1. Loss-of-function mutation in ZOP1 suppresses snc2-1D-mediated autoimmunity, while zop1 single mutants exhibit compromised resistance against pathogens. RNA-seq analysis revealed that many defense response genes are differentially expressed or have altered splicing patterns in the zop1 mutant. The genes down-regulated in the zop1 mutant include BDA1 and RLP23, which encode two key regulators of plant defense. Overall, our study suggests that ZOP1 contributes to the regulation of plant immunity.