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 60 g (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-sequencing analysis revealed that many defense response genes are differentially expressed or have altered splicing patterns in the zop1 mutant. The genes downregulated 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.