Molecular Characterization,Functional And Polymorphism Studies Of Myostatin Gene From The Banana Shrimp Fenneropenaeus Merguiensis

Myostatin is an important member of the Transfor ming Growth Factor(TGF)family that functions to negative regulate muscle growth and development in animals.Fenneropenaeus merguiensisis a large penaeid shrimp that constitutes a major species in shrimp fisheries.The interest in aquaculture of this species has increased in recent years as the outbreaks of shrimp diseases have affected the global aquaculture of the more common shrimp,L.vannamei.In this study,a full length FmMstn gene and two slightly different(short and long forms)cDNAs generated from the use of the alternative splice site between exon 1 and intron 1 were cloned and characterized.Similar to Mstn gene of the scallop,fish and mammal,FmMstn gene consists of 3 exons and 2 introns.FmMstn gene promoter consists of 2160 bp with putative elements including E-boxes,CAAT box,TATA box and myocyte enhancing factor(MEF)considered as important marker sequence in many muscle-related gene.The open reading frame of the short Mstn consists of 1260 bp encoding for a protein with 420 a mino acid residues.The long FmMstn is almost identical to the short FmMstn with the exception of 8 a mino acid(GNNYTSQS)insertion.FmMstn is most similar to the Mstn of Litopenaeus vanname and Penaeus monodon sharing >95% a mino acid sequence identity.Multiple sequence alignment results revealed the conservation of 2 furin-like cleavage sites(RXXR),9 cysteine residues and TGF functional domain in the mature peptide with Mstn from other animals.Real-time PCR results revealed high levels of FmMstn transcripts were detected in the heart,muscle,eyestalk and thoracic ganglion but only traces of FmMstn transcript were detected in other tissues;FmMstn transcript level in muscle is higher in early postmolt,decreases in intermolt and increases again towards ecdysis.Higher expression level of FmMstn is also observed in smaller shrimp of the same age.Knock-down of FmMstn by RNAi can cause a significant increase in molt cycle duration and failure of some shrimp to undergo ecdysis.Direct DNA sequencing results revealed that FmMstn gene is highly polymorphic and several potential SNPs have been identified.In summary,the result of this study indicates that FmMstn is molt/growth-related and the presence of SNP suggests that it could be a candidate gene for shrimp genetic improvement research.