Abstract:CalciumDependent Protein Kinase is a key enzyme and plays an important role in the signal transduction pathways of plant stress resistance. In this study, using reverse transcriptionPCR and rapid amplification of cDNA ends (RACE) techniques, we cloned EkCDPK gene from Epimedium koreanum Nakai, its fulllength about 2 036 bp. The results showed that: (1) EkCDPK gene cDNA is 1 410 bp, 5′UTR is 387 bp and 3′UTR is 239 bp,and the ORF encodes for 469 amino acid. Conserved domain of EkCDPK protein consists of S_TKc domain in N end and EFhand domain in C end. EkCDPK was predicted to be a stable hydrophilic protein, possessing a typical and conserved serine/threonine protein kinase domain and a transmembrane structure domain, also an ATP site, 4 Ca2+ binding sites, and without signal peptide. The secondary structure of EkCDPK is abundant in αhelices (43.71%) and random coils (37.10%). (2) The phylogenetic relationship analysis showed that EkCDPK is closely related to Isatis tinctoria (95%). (3) The qRTPCR results showed that EkCDPK gene expressed in root, stem, leaf and flower tissues, with the highest expression in root, followed by stem. After drought stress, EkCDPK expression was significantly higher than that in the control group in 15 h, then began to decrease, and its life index decreased too. After salt stress 5, 15 and 25 h, its expression was significantly higher than that of control group. (4) pET28aEkCDPK prokaryotic expression vector was constructed and induced the expected size protein, which is about 50 kD, indicating recombinant protein EkCDPK was expressed successfully. These results provided a basis for the further study on improving the plant stress resistance of E. koreanum Nakai using genetic engineering.