Molecular Cloning And Polymorphisms Of Leptin-a Gene Associatied With Growth Traits In Golden Pompano (Trachinotus Blochii)

The golden pompano(Trachinotus blochii)is an important marine economic fish in China,due to its tastes delicious and high domestic and international market demand.In recent years,with golden pompano long-term breeding,faced with frequent disease,slow growth and other issues,which make farming costs rise.So it’s necessary to breed the varieties with excellent traits.Molecular-marker assisted selection(MAS)breeding have promoted the process of new variety breeding in fishes.In this research,the leptin-a gene from golden pompano were isolated,SNP of this gene were detected,and analyses of the SNP with growth traits.The results are as follows:1.The full genomic sequences of leptin-a gene from Trachinotus blochii were isolated.(1)The cDNA of Trachinotus blochii leptin-a was 1265bp.(2)The DNA of Trachinotus blochii leptin-a was 2019bp,exonl was 28bp,intronl was 665bp,exon2 was 150,intron2 was 89bp,exon3 was 336bp,containing a 486 bp open reading frame(ORF)with a coding potential for a 161-amino acid protein.(3)The 5’-flanking region of leptin-a gene was 1932bp,it obtained using genome walker method.2.By analysises of jellyfish software and leptin/leptin-a structure of known species,we can predict that leptin-a protein signal peptide is first 20 amino acids of amino terminal,leptin-a mature peptide is others 141 amino acids of carboxy terminal.Molecular mass of leptin-a protein is predicted to 17.9kDa by analysises of bioinformatics software.Conducted a comparative analysis Trachinotus blochii amino acid sequence of leptin-a protein its predicted by jellyfish software and known vertebrate acid sequences of leptin/leptin-a protein get in NCBI genebank.Then conducted molecular phylogenetic analysis by an online software.Homology comparison results show that amino acid sequence of leptin-a protein of Trachinotus blochii is low homologous to mammals and amphibians(16.9%~18.5%).Even in teleost fish,Trachinotus blochii is low homologous to amino acid sequence of leptin protein of other order(22.2%~54.9%),only in same order have highly homologous(76.4%~87.6%).3.Using direct sequencing,the leptin-a gene SNPs were detected in Trachinotus blochii,and association analyses between these polymorphisms and ten growth traits were performed.Ten polymorphisms,consisting of five SNPs in intron 1(C203T,G252A,C380G,G383C,G587A),one mutation in exon 2(T775A),one mutation in exon 3(G1239A),and three SNPs in 3’-untranslated region(3’-UTR)(G1424A,T1653A,A1654 T)were identified and genotyped in 150 individuals.Association analyses revealed that the T775A polymorphism was significantly associated with body weight(BWT),body height(BWH),body length(BL),and overall length(OL),and that the homozygous mutation genotype TT had negative effects on growth traits.Additionally,the SNP G123 9A wa:s significantly associated with BWT,BWH,OL,and head length(HL),with the GA genotype showing positive effects on growth traits.