The Polymorphism In The Coding Region Of IGF1 And IGF2 Related To Its Transcription In And The Growth Of Male And Female Half-smooth Tongue Sole (Cynoglossus Semilaevis)

1. The polymorphism in the coding region of IGF1 related to its mRNA expression and the growth traits of male half-smooth tongue sole(Cynoglossus semilaevis)Insulin-like growth factor 1 (IGF1) is involved in the growth endocrine regulation of many fish species. The purpose of this study was to detect the single nucleotide polymorphism (SNP) in the coding region of IGF1 and analyze the relationships among genotypes, growth traits, serum levels of physiological and biochemical indexes and gene expression in male half smooth tongue sole (Cynoglossus semilaevis). A mutation at 884 bp position was detected in exon 5 of IGF1, which was named C884A. This mutation occurred after termination codon in the structure of WD40 domain, thus influenced the transcription, growth characteristics among others. This mutation has significant correlations with body weight (P< 0.05) and viscera weight (P< 0.05). AA genotype was significantly higher than AB genotype in weight (P< 0.05) and viscera weight (P< 0.05). The UERA content of AA genotype was significantly higher than the AB genotype (P< 0.05). At the same time, the expression of AA genotype was also significantly higher than AB genotype (P< 0.01). These results indicated that the polymorphism of IGF 1 in encoding region was significantly associated with the growth traits, blood physiological and biochemical indexes and gene expression in male half smooth tongue. The mutation can be used as a molecular marker for selection breeding. Our findings may assist molecular breeding of good varieties from a genetic perspective and improve the production in male half smooth tongue sole.2. The polymorphism in the coding region of IGF1 related to its mRNA expression and the growth traits of female half-smooth tongue sole(Cynoglossus semilaevis)In this study, SSCP and DNA sequencing were used to detect single nucleotide polymorphisms (SNPs) in coding areas oflGFl geneand the relationshipsamong genotypes and growth traits and gene expression were analyzed in female half smooth tongue sole. Research results were the same as the male. A mutation in 884 bp locuswas detectedin exon 5 of IGF1 gene, named C884A.This mutation occurred after termination codon,because of it occurred in the structure of WD40 domain, thus influenced gene transcription and expression, growth characteristics, etc.Thislocalhas significant correlation with body weight (P<0.01) and viscera weight (P<0.01).The difference with male, ABgenotype was considered much higher than AA genotype in body weight (P<0.01) and viscera weight(P<0.01). The expression of AB genotype was also significantly higher than AA genotype (P<0.01).Moreover, there is another tendency that AB genotype individuals are higher than the AA genotype in other aspects such as body height and GSI, but this difference is not obvious (P>0.05). These results indicated that the mutationoflGF1 gene encoding areas can be used as a perfect molecular marker for selection breeding.3. The polymorphism in the coding region of IGF2 related to its mRNA expression and the growth traits of female and male half-smooth tongue sole (Cynoglossus semilaevis)Insulin-like growth factor2 (IGF2) is involved in growth endocrinology regulation in many fishes. Two SNPs (SNP1 and SNP2) of IGF2genewerediscovered in malehalf-smooth tongue sole. Four diplotypes(D1, D2, D3 and D4)were created based on the two SNPs. However, SNP1 was repaired in the process of transcription. SNP2 exert significant effects on body weight (P<0.01), eviscerated weight (P<0.01) and liver weight (P<0.05) oflGF2gene. T test shows that AA genotype of SNP2 has a much higher body weight (P<0.01),eviscerated weight (P<0.01) and liver weight (P<0.05) than AB genotype.D2 and D4 genotype has a much higher body weight (P<0.05) andeviscerated weight (P<0.01) than D1 genotype. The Total protein (TP) content of AA genotype is significantly higher than the AB genotype (P<0.05). In addition,the mRNA expression level ofAA genotype was higher than AB genotype(P<0.01).The mRNA expression level of diplotypes (D2 and D4) weresignificantly higher than D1 diplotypes(P<0.05). The SNP1 is the same in male and female half-smooth tongue sole. However, SNP2 did not appear in female half-smooth tongue sole.Above all, the study of gene encoding of IGF2gene showed that the mutations of IGF2 gene were correlated with growth characters, blood biochemistry and gene expression in male half-smooth tongue sole. Significantly, this study has certain reference value in fish molecular biology research.