Insights on Calcium-Dependent Protein Kinases (CPKs) Signaling for Abiotic Stress Tolerance in Plants

Abiotic stresses are the major limiting factors influencing the growth and productivity of plants species. To combat these stresses, plants can modify numerous physiological, biochemical, and molecular processes through cellular and subcellular signaling pathways. Calcium-dependent protein kinases (CDPKs or CPKs) are the unique and key calcium-binding proteins, which act as a sensor for the increase and decrease in the calcium (Ca) concentrations. These Ca flux signals are decrypted and interpreted into the phosphorylation events, which are crucial for signal transduction processes. Several functional and expression studies of different CPKs and their encoding genes validated their versatile role for abiotic stress tolerance in plants. CPKs are indispensable for modulating abiotic stress tolerance through activation and regulation of several genes, transcription factors, enzymes, and ion channels. CPKs have been involved in supporting plant adaptation under drought, salinity, and heat and cold stress environments. Diverse functions of plant CPKs have been reported against various abiotic stresses in numerous research studies. In this review, we have described the evaluated functions of plant CPKs against various abiotic stresses and their role in stress response signaling pathways.