Arabidopsis CPK3 plays extensive roles in various biological and environmental responses.

Plant Ca(2+)-dependent protein kinase (CPK) signaling is involved in a wide array of intracellular signaling pathways involved in stomatal movement and plant adaptation to various environmental challenges including drought, salt and cold stress. Arabidopsis CPK3 appears to be extensively involved in such a wide range of aspects, and has been shown to function in mediating the signaling following Ca(2+) influx after insect herbivory. The results reveal the involvement of CPK3 in the herbivory-induced signaling network through phosphorylating the substrate target HsfB2a (heat shock transcription factor) for transcriptional activation of the plant defensin gene PDF1.2. Proteomic studies based on the cell-free protein production system allowed us to mine CPK3 targets more extensively and clarify the nature of multifunctional CPK3.