Abstract: The cDNA sequence of Pinctada maxima CCT-eta (PmCCT-eta) was cloned by rapid amplification of cDNA ends method (RACE) and bioinformatics analysis of PmCCT-eta was conducted. The distribution of PmCCT-eta in various tissues and the induced expression of PmCCT-eta under cold stress in Pinctada maxima were studied by real-time PCR. The results showed that the full length of PmCCT-eta cDNA was 1895 bp, which contained a 1632 bp ORF encoding 543 aa. Three CCT-eta signature sequences (₃₇RTTLGPRGMDKLI₄₉, ₅₈ISNDGATILKTLDIVHP₇₄, ₈₆QDAEVGDGT₉₄) and three functional structure domains (Equatorial domain, Apical domain, Intermediate domain) were found in the deduced protein of PmCCT-eta. Homology analysis indicated that the deduced protein of PmCCT-eta had 83.2%, 80.1% and 79.3% similarity with CCT-eta of Crassostrea gigas, Danio rerio and Homo sapiens, respectively. PmCCT-eta mRNA expression in all tissues was observed, with highest expression in adductor muscle and lower expression in heart and hepatopancreas. The PmCCT-eta mRNA expression was up-regulated in adductor muscle, heart and hepatopancreas of Pinctada maxima under cold stress condition. However, different tissues had distinct response patterns; heart and hepatopancreas responded faster than adductor muscle, suggesting that CCT-eta plays an important role in resisting cold stress in internal organs such as heart and hepatopancreas.

Key words: Pinctada maxima, CCT-eta, cDNA, tissue expression, cold stress