Molecular characterization of HbCDPK1, an ethephon-induced calcium-dependent protein kinase gene of Hevea brasiliensis.

Calcium-dependent protein kinases (CDPKs), as major primary Ca(2+) sensors, have been implicated in the regulation of stress and developmental signals in plants. In this study, a novel CDPK gene, designated HbCDPK1, was isolated from Hevea brasiliensis. The HbCDPK1 cDNA had 2,400 bp with an open reading frame of 1,671 bp encoding 556 amino acids, and the deduced HbCDPK1 protein contained four characteristic domains identified in CDPKs, showing a high level of sequence similarity to CDPKs from other plants. Expression analysis revealed more significant accumulation of the transcripts of HbCDPK1 in latex than in the leaves, bark, and roots in H. brasiliensis. In addition, transcription of HbCDPK1 was strongly induced by mechanical wounding, jasmonic acid (JA), and ethephon. Recombinant HbCDPK1 was expressed in E. coli, and its activity was assayed. The assay indicated that HbCDPK1 had the kinase and Ca(2+)-binding activity in vitro as a calcium-dependent protein. The potential roles of the HbCDPK1 are discussed as to latex production and rubber biosynthesis.