| The hard clam Meretrix meretrix is an important commercially shellfish which is widely cultured in the coast of China.It has the reputation of "the freshest in the world"because of its tender meat and rich nutrition.It is welcomed by domestic and foreign consumers,and is one of the fresh aquatic products exported in largequantities in China.At present,the traditional selective breeding is adopted in the cultivation of M.meretrix.In order to speed up the breeding of new varieties with high quality,high yield and strong resistance to stress,it is important to study the growth regulation mechanism of functional genes such as growth and development of M.Meretrix for developing molecular marker-assisted selection breeding technology.It can speed up the shortening of breeding cycle and promote the healthy development of clam breeding industry.In this study,three growth-related genes,BMP2,BMP7 and TGF-β R1,were cloned based on the annotation information of M.Meretrix transcriptome library.Spatiotemporal expression of MmBMP2 and MmBMP7 genes and growth-related SNP loci were studied.The growth-related SNP loci were screened for the exons of MmTGF-β R1 gene.These works provide a theoretical basis for using molecular marker-assisted breeding technology to cultivate new strains of M.Meretrix with high quality.The results are as follows:(1)The full length of MmBMP2 gene is 2641 bp,with the open reading frame is 1395 bp,encoding 464 amino acids.It has signal peptide and no transmembrane region.MmBMP2 protein contains a domain,which is a TGF-β superfamily domain(363Cys-464Arg).Amino acid multiple sequence comparison showed that the MmBMP2 had the highest homology with CfBMP2(53.1%)and 43%-53%with other organisms.In adult clams,the expression of MmBMP2 in the mantle was the highest and extreme significantly higher than that of other five tissues(P<0.01),suggesting that it might be involved in shell growth.Among the seven developmental stages,MmBMP2 transcript in the juvenile clams was expressed highest(P<0.05),followed by unfertilized mature eggs,blastula,gastrulae and eyespots larva,the lowest expression in 4-cell embryo and trochophore.Two common growth-related SNP loci(A726G and A732T)were found in the exon region of MmBMP2 gene in two groups,suggesting that the gene may be related to the growth of M.meretrix,and could be used as candidate genes for molecular marker-assisted breeding.(2)The full length of MmBMP7 gene is 3161 bp,with the open reading frame is 1257 bp,encoding 418 amino acids.It has a potential transmembrane domain,which is a TGF-β superfamily domain(281 Arg-418 His).Amino acid multiple sequence comparison showed that the MmBMP7 gene had the highest homology with PfBMP7(58.7%)and the homology with other organisms was between 44.4%and 57.6%.And MmBMP7 expression profiles showed that MmBMP7 gene was expressed highest in the adult mantle,and was significantly higher than that in other tissues(P<0.05).During the developmental stages,unfertilized mature eggs,blastula,gastrula,trochophore and juvenile clams were highly expressed(P<0.05),which may be involved in the formation of the morphogenesis and the hard shell.Two SNP loci(C32T and G144A)were found to be significantly correlated with growth traits in JS group,but no SNP loci related to growth traits were found in WL2 group.(3)The full length of MmTGF-β R1 gene was 2357 bp,with the open reading frame was 1542 bp,encoding 513 amino acids.Smart predicted that TGF-β R1 protein contained two domains,one was GS domain(177Ser-205Ile)and the other was S-TKc domain(205Ile-493Leu).The results of amino acid sequence alignment showed that MmTGF-β R1 gene had the highest homology with CfTGF-β R1(63.08%)and 50.93%～62.65%with other organisms.SNP loci were screened in exon region of MmTGF-β R1.It was found that one SNP locus(A427T)was significantly correlated with growth traits in JS group,but no SNP loci related to growth traits were found in WL2 group. |
PDF Full Text Request