CPK28-NLP7 module integrates cold-induced Ca(2+) signal and transcriptional reprogramming in Arabidopsis

Exposure to cold triggers a spike in cytosolic calcium (Ca(2+)) that often leads to transcriptional reprogramming in plants. However, how this Ca(2+) signal is perceived and relayed to the downstream cold signaling pathway remains unknown. Here, we show that the CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28) initiates a phosphorylation cascade to specify transcriptional reprogramming downstream of cold-induced Ca(2+) signal. Plasma membrane (PM)–localized CPK28 is activated rapidly upon cold shock within 10 seconds in a Ca(2+)-dependent manner. CPK28 then phosphorylates and promotes the nuclear translocation of NIN-LIKE PROTEIN 7 (NLP7), a transcription factor that specifies the transcriptional reprogramming of cold-responsive gene sets in response to Ca(2+), thereby positively regulating plant response to cold stress. This study elucidates a previously unidentified mechanism by which the CPK28-NLP7 regulatory module integrates cold-evoked Ca(2+) signal and transcriptome and thus uncovers a key strategy for the rapid perception and transduction of cold signals from the PM to the nucleus.