Cyclic nucleotide-gated channels 14, 15, and 16 coordinate multiple signaling pathways to promote salt tolerance in...

Plants activate osmotic regulation, ion and reactive oxygen species (ROS) homeostasis modulation, and plant hormone abscisic acid (ABA)-mediated stomatal movement regulation for survival under salt stress. However, it is unknown if and how a single molecule coordinates multiple responses. Here we characterized the functions of three closest homologs, cyclic nucleotide-gated channel 14, 15, and 16 (OsCNGC14/15/16), in regulating multiple signaling pathways in response to salt. Mutants of each of these three genes had reduced salt tolerance compared to the wild type. These mutants also had slower stomatal closure, lower Ca²⁺ influx, higher Na⁺/K⁺ ratio, and ROS accumulation under salt treatment. Conversely, overexpression of OsCNGC16 led to enhanced salt tolerance, increased Ca²⁺ influx, lower Na⁺/K⁺ ratio, and ROS accumulation in response to salt. OsCNGC14/15/16 also positively regulate shoot growth under ABA treatment. Exogenous ABA treatment rescued the defects in salt tolerance and stomatal closure of the OsCNGC16 mutant. And treatment of ROS scavenger dimethylthiourea (DMTU) partially rescued the salt susceptibility of the OsCNGC16 mutant. In addition, OsCNGC16 can interact with and be phosphorylated by Ca²⁺-dependent protein kinases 5 and 13 (CPK5/13). This study unveils multiple roles of OsCNGC14/15/16 proteins in salt tolerance and identifies common regulators of stomatal closure, Ca²⁺ influx, Na⁺/K⁺ homeostasis, ROS scavenging, and ABA signaling in response to salt stress.