双棘黄姑鱼IGF2基因克隆及其在卵巢发育中的作用研究

IGF2 gene cloning and its function during the development of ovarian cycle in Protonibea diacantus

运用RT-PCR和RACE技术,首次克隆了双棘黄姑鱼(Protonibea diacanthus)的IGF2 cDNA。双棘黄姑鱼IGF2cDNA全长842bp,其中开放阅读框为648bp,5′非翻译区为125bp,3′非翻译区为69bp。IGF2前体mRNA编码215个氨基酸,成熟肽为71个氨基酸残基的多肽。多重氨基酸比对结果显示,双棘黄姑鱼与其他鱼类IGF2氨基酸序列高度保守。同源性分析表明,双棘黄姑鱼IGF2氨基酸序列与同属鲈形目的斜带石斑鱼、金头鲷、罗非鱼同源性分别为95.8%、95.3%和91.2%。系统进化树结果与同源性分析结果相似,双棘黄姑鱼IGF2基因首先与同属鲈形目的斜带石斑鱼、金头鲷、罗非鱼类聚,再与虹鳟、牙鲆、黄颡鱼的IGF2和斑马鱼IGF2b基因聚为一支,最后与斑马鱼IGF2a类聚为鱼类IGF2基因。组织分布结果表明,IGF2基因在双棘黄姑鱼各组织中表达广泛。RT-PCR结果显示,双棘黄姑鱼卵巢成熟期和退化期的IGF2表达量显著高于发育期,推测IGF2的表达可能促进了双棘黄姑鱼卵巢的成熟。

IGF cDNA of Protonibea diacanthus was obtained by using the method of RACE and RT-PCR for the first time in this study. The full length sequence is 842 bp, which contains 648 bp open reading frame （ORF）, 125 bp 5＇ untranslated region （UTR）, and 69 bp 3＇ untranslated region. IGF2 precursor mRNA encodes 215 amino acids, while the mature polypeptides contains 71 amino acid residues. IGF2 of Protonibea diacanthus has a high homology with that of other fishes. It has 95.8%, 95.3%, 91.2% homology with Epinephelus coioides, Sparus aurata, Oreochromis niloticus, respectively. Phylogenetic tree analysis shows that the IGF2 of Protonibea diacanthus tends to cluster with E. coioides, S. aurata, O. niloticus of the same genus firstly, then clusteres with IGF2 of Oncorhynchus mykiss,letalurus Punetaus, Pelteobagrus fulvidraco and IGF2b of Danio rerio in turn. Finally IGF2a of Danio rerio is clustered in the same branch with bony fishes＇ IGF2. Tissue distribution shows that IGF2 is widely expressed in multiple tissues of P. diacanthus. RT-PCR reveales that the highest expression of IGF2 of ovary is detected in maturation phase and regression phase than that development phase. IGF＇2 expression may relate with ovarian maturation of P. diacanthus.