Molecular Cloning, Characterization and Expression Profile of Myf5 and Myf6 During Growth and Development in the Seriola lalandi

Myogenic Regulatory Factors (MRFs) is involved in the muscle growth and differentiation. In this study, the cDNA sequence of yellowtail kingfish MRFs genes were cloned by rapid amplification of cDNA ends (RACE) method; then, the characteristics of these genes and the predicted protein sequences were analyzed by bioinformatics methods, the tissue and embryonic stages differential expression pattern were detected by the quantitative real-time PCR. Our results showed that the yellowtail kingfish (YTK) Myf5 cDNA has a full length of 951 bp, encoding 266 amino acids. The yellowtail kingfish Myf6 cDNA has a full length of 1105 bp, encoding 250 amino acids. The proteins contain α-helix, β-strand, and loops. The Neighbour-joining tree revealed that YTK Myf5 and Myf6 are closely related to Seriola dumerili . The yellowtail kingfish Myf5 and Myf6 gene expressed significantly higher in muscle than in other tissues ( P <0.05). In addition, Myf5 and Myf6 in muscle was significantly expressed in 400 g and 500 g fish but not in 50 g, suggesting that myogenic regulatory factors expression had a great relationship with the fish size. Our results also indicated that Myf5 and Myf6 have different functions during embryonic development, because Myf5 showed highest expression level at the neuroembryo period, but Myf6 had the highest expression level at embryo coverage yolk 70% stage. Myf5 gene showed highest expression at 30 d of age, suggesting it played key roles in myogenic period. However, the Myf6 gene was significantly highly expressed at 60 d, revealing this gene functioned in the later muscle formation period.