Abstract:Onchidium struma belongs to Mollusca, Pulmonata, and was regarded as the transitional taxa from water to land because of its amphibious characteristics. Having similar characters to amphibians, O. struma is a good subject for the study of marine invertebrates extending landward. As the basic component of muscle units, myosin directly influences the muscle growth and meat quality via its molecular diversity and composition. It is a ubiquitous eukaryotic motor protein that interacts with actin to generate the force for cellular movements, ranging from cytokinesis to muscle contraction. In this study, we used rapid amplification cDNA ends (RACE) methods to obtain the full-length cDNA of the myosin heavy chain (MyHC) gene in O. struma. We performed bioinformatic and expression pattern analysis of MyHC mRNA in different tissues detected by real-time fluorescent quantitative PCR (qRT-PCR). The full length of the MyHC cDNA sequence consists of 7566 base pairs (bp) comprising a 228 bp 5' untranslated region (UTR), a 1443 bp 3' UTR, and a 5895 bp open reading frame (ORF) which encodes 1964 amino acids. MyHC gene was expressed in various tissues; its highest expression was found in the foot and its lowest in the hepatopancreas (P<0.05). Moreover, the MSTN protein was predicted to be composed of 31,713 atoms and its formula is C9765H15897N2849O3150S52, with a calculated relative molecular weight of 225.28 kDa and a pI of 5.56. The result of signal peptide prediction shows that the N-terminal has a signal peptide of 29 amino acids in length. Additionally, common features were found in the MyHC of O. struma, including MYSc class II and myosin tail l domain. Molecular phylogenetic analysis shows that O. struma is closely related to Biomphalaria glabrata. This study provided a novel myosin heavy chain gene sequence in O. struma and the results indicate that the MyHC gene is important for the growth and development of this animal, as well as its muscle characterization. Furthermore, the results revealed that MyHC is not only an essential structural protein, but also a functional protein in O. struma. Conclusively, MyHC is an excellent candidate gene for studying biological evolution.
