The Zygotic Division Regulator ZAR1 Plays a Negative Role in Defense Against in .

A phosphorylation/dephosphorylation cycle at tyrosine 428 of CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1) plays an essential role in chitin triggered immunity in . In this study, we used a differential peptide pull-down (PPD) assay to identify factors that could participate downstream of this cycle. We identified ZYGOTIC ARREST 1 (ZAR1) and showed that it interacts with CERK1 specifically when the tyrosine 428 (Y428) residue of CERK1 is dephosphorylated. ZAR1 was originally characterized as an integrator for calmodulin and G-protein signals to regulate zygotic division in . Our current results established that ZAR1 also negatively contributed to defense against the fungus and played a redundant role with its homolog ZAR2 in this process. The double mutant exhibited stronger resistance to compared with single mutant, single mutant, and wild-type plants. Moreover, the inducible expression of numerous defense response genes upon infection was increased in the double mutant, consistent with a repressive role for ZAR proteins in the defense response. Therefore, our findings provided insight into the function of ZAR1 in multiple defenses and developmental regulation pathways.