A calcium sensor kinase pathway interacts with the TOR complex to balance growth and salt tolerance in Arabidopsis

Soil salinity negatively affects crop yields worldwide. The dynamic transition between growth and salt stress responses helps plants cope with changing soil salinity status. However, the molecular mechanisms controlling such dynamic transitions remain poorly understood. Here, our study identified the target of rapamycin complex (TORC) as a central player in growth recovery from salt stress. We observed a rapid decline in TORC activity in Arabidopsis thaliana plants upon exposure to salt stress. Further investigation uncovered an intricate interplay between TORC and a salt response signaling network comprising calcineurin B-like (CBL) proteins and CBL-interacting kinases (CIPKs). Under standard growth conditions, Regulatory-Associated Protein of TOR (RAPTOR) promotes CBL-CIPK complex dissociation, thereby inhibiting CIPK. CIPK suppression is lifted under salt stress, and the activated CBL-CIPK complex phosphorylates RAPTOR, which in turn suppresses TORC activity. Thus, the reciprocal regulation of the TORC and CBL-CIPK modules orchestrates plant responses and adaptation to soil salinity.