PaCDPK1, a gene encoding calcium-dependent protein kinase from orchid, Phalaenopsis amabilis, is induced by cold, wounding, and pathogen challenge

Signaling pathways, specifically calcium and calcium-dependent protein kinase (CDPK), have been implicated in the regulation of stress and developmental signals in plants. Here, we reported the isolation and characterization of an orchid, Phalaenopsis amabilis, CDPK gene, PaCDPK1, by using the rapid amplification of cDNA ends (RACE)-PCR technique. The full length cDNA of 2,310 bp contained an open reading frame for PaCDPK1 consisting of 593 amino acid residues. Sequence alignment indicated that PaCDPK1 shared similarities with other plant CDPKs. PaCDPK1 transcripts were expressed strongly in labellum but not in leaves and roots. In addition, the PaCDPK1 gene was transcriptionally activated in response to low temperature, wounding, and pathogen infection. To identify the regulatory role of the PaCDPK1 promoter, a construct containing the PaCDPK1 promoter fused to a β-glucuronidase (GUS) gene was transferred into Arabidopsis by Agrobacterium-mediated transformation. GUS staining revealed that PaCDPK1/GUS expression was induced by cold, wounding, and pathogen challenge in leaves and stems of transgenic Arabidopsis. These results suggested that this PaCDPK1 gene promoter could be used as an endogenous promoter for biotechnological purposes in orchids.