Plant Stress Responses Mediated by CBL-CIPK Phosphorylation Network

At any given time and location, plants encounter a flood of environmental stimuli. Diverse signal transduction pathways sense these stimuli and generate a diverse array of responses. Calcium (Ca²⁺) is generated as a second messenger due to these stimuli and is responsible for transducing the signals downstream in the pathway. A large number of Ca²⁺ sensor-responder components are responsible for Ca²⁺ signaling in plants. The sensor-responder complexes calcineurin B-like protein (CBL) and CBL-interacting protein kinases (CIPKs) are pivotal players in Ca²⁺-mediated signaling. The CIPKs are the protein kinases and hence mediate signal transduction mainly by the process of protein phosphorylation. Elaborate studies conducted in Arabidopsis have shown the involvement of CBL-CIPK complexes in abiotic and biotic stresses, and nutrient deficiency. Additionally, studies in crop plants have also indicated their role in the similar responses. In this chapter, we review the current literature on the CBL and CIPK network, shedding light into the enzymatic property and mechanism of action of CBL-CIPK complexes. We also summarize various reports on the functional modulation of the downstream targets by the CBL-CIPK modules across all plant species.