Abstract
Ca2+ signals have evolved a wide spectrum of strategies as intra/intercellular signals. Even though Ca2+-binding sensory proteins like Ca2+-dependent protein kinase (CDPK) are expected to act as intracellular protein mediators that govern gene regulation networks in response to Ca2+ influx after herbivory, little is known about the mechanisms. To investigate whether CDPKs play certain roles in an herbivore response-signaling pathway, we screened the characteristics of Arabidopsis CDPK mutants damaged by a feeding generalist herbivore, Spodoptera littoralis. After herbivory, the cpk3 and cpk13 mutants showed lower transcript levels of plant defensin gene PDF1.2 compared to wild-type plants. in vitro Kinase assays of the CDPK proteins with defense-related transcription factors (TFs) demonstrated that CPK3 phosphorylates TFs and ATL2 as substrate targets. The results presented show that CDPKs are involved in controlling the herbivore-induced expression of plant defensin gene, and that they exert such control by interacting with transcription factors.
