Abstract：Hyriopsis cumingii is an important pearl-breeding mussel in China, and it grows fast and breeds pearls of good quality. In this study, We cloned a full-length cDNA sequence of myosin essential light chain gene(MELC) which was isolated from the mantle of Hyriopsis cumingii according to homology cloning strategy and SMART RACE-PCR technique. The full length cDNA sequence was 1 119 bp, comprising a complete open reading frame of 468 bp which encoded 155 aa of 17.49 kD and pI at 4.53. The GenBank accession number was JX275828. MELC included two consertive EF-hand Ca2+-binding domains which analysed by PROSITE tool, and which belonged to EF-hand Ca2+-binding protein family. The amino acid sequences of MELC gene possessed 69%, 69% and 68% identity with Pinctada fucata, Crassostrea gigas and Haliotis discus discus, respectively. Quantitative Real-time PCR analyses showed that MELC gene was ubiquitously expressed in all tissues of H. cumingi, including adductor muscle, mantle, gill, axe foot, gonad, heart, liver, gut, especially strongly expressed in tissues related with calcium metabolism, such as mantle, gill and axe foot, which were higher than liver and gonad. The result implied MELC gene might take an important part in the calcium metabolic process of H. cumingii. Moreover, the expression of MELC gene in mantle of H. cumingii went up and came down along with the rising of Ca2+ concentration, then reached a climax at 60 mg/L, which demonstrated that the suitable Ca2+ concentration would accelerated the high expression of MELC gene, otherwise, it might inhibit the expression of MELC gene. All these results indicate MELC gene in H. cumingii may play an important role in Ca2+ uptake, transport, storage, and participate in the formation of pearls.
