Cloning and Expression of Calcium-dependent Protein Kinase 15 (NtCDPK15) in Nicotiana tabacum

Calcium-dependent protein kinases(CDPKs) play important roles in regulating downstream components in calcium signaling pathways. NtCDPK15 (GenBank Accession No. JN662020), was isolated from common tobacco (Nicotiana tabacum) by rapid amplification of cDNA ends (RACE). The NtCDPK15 cDNA is 1963 bp long and contains an open reading frame (ORF) of 1569 bp encoding 522 amino acids. Sequence alignments indicated that NtCDPK15 was a typical CDPK which had well-conserved C-terminal calmodulin-like structure with 4-EF hand motifs for calcium-binding. Phylogenetic analysis indicated the NtCDPK15 might originate from Nicotiana tomentosiformis, and NtCDPK15 and NtCDPK1 might correspond to conserved functions. The results of real-time quantitative reverse transcription-PCR (qRT-PCR) showed that the relative expression of NtCDPK15 in roots and leaves was significantly higher than those in stems, but highly increased in stems treated with high-salt. Salt stress and ABA treatment made the relative expression of the gene increased in leaves and roots, but the gene expression was lowered subjected to drought stress in roots and leaves. These indicate that in common tobacco NtCDPK15 is induced by high-salt and ABA stresses, and suppressed by drought stress.