CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 regulates salt tolerance through CATALASE 2 in Arabidopsis

Abstract Soil salinization threatens global crop production. Here, we report that a receptor-like cytoplasmic kinase (RLCK), CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 (CRCK3), plays an essential role in plant salt tolerance via CATALASE 2 (CAT2), a hydrogen peroxide (H2O2)-scavenging enzyme in Arabidopsis (Arabidopsis thaliana). CRCK3 was induced by salt stress, and its knockout mutant displayed a salt-sensitive phenotype compared to wild-type (WT) plants. CRCK3 was activated by salt stress in a calcium-dependent manner, and its kinase activity was required for plant salt tolerance. CRCK3 physically interacted with CAT2, and CRCK3-mediated salt tolerance depended on CAT2. Salt treatment significantly induced CAT2 phosphorylation via the action of CRCK3, and this phosphorylation was required for CAT2-mediated H2O2 scavenging to reduce ROS content and oxidative damage in plants under saline conditions. CRCK3 phosphorylated CAT2 at the Thr209 residue, resulting in elevated catalase activity to reduce reactive oxygen species (ROS) accumulation under saline conditions. Therefore, the CRCK3-CAT2 module mediates plant salt tolerance by maintaining redox homeostasis. This study expands our knowledge of how plants respond to salt stress.