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斑马鱼(Danio rerio)中蝶啶代谢通路调控蝶啶色素合成,而GTP环化水解酶1基因(GTP cyclohydrolase 1,Gch1)是该代谢通路的限速酶。锦鲤(Cyprinus carpio var.koi)是一种被广泛养殖的观赏鱼,有多种的体色组合模式。为了研究锦鲤Gch1基因的功能、保守性及在不同体色的表达模式,本研究组装鲤(Cyprinus carpio)高通量转录组数据,并依此扩增获得锦鲤Gch1全长c DNA序列(Gen Bank登录号:KP056544)。该基因编码一个由251个氨基酸组成的蛋白。结构域分析发现,该蛋白含有GTPcyclohydrolaseⅠ功能域。Gene Ontology注释发现,该蛋白具有水解酶活性分子功能,并参与细胞内含氮化合物代谢和细胞内氨基酸代谢过程。多物种Gch1同源性比较发现,该基因较为保守。适应性进化分析发现,锦鲤与斑马鱼Gch1的非同义替换率(the number of nonsynonymous substitutions per nonsynonymous site,Ka)与同义替换率(the number of synonymous substitutions per synonymous site,Ks)比值为0.06,说明该基因在进化中受到强烈负选择压。研究结果表明,锦鲤Gch1参与蝶啶代谢通路;Gch1在红皮的表达水平显著高于白皮的(P<0.05),提示该基因高表达可能导致体色变红。本研究首次阐明Gch1在锦鲤红白体色间的表达差异,为进一步研究Gch1在锦鲤其他体色变化的作用机理提供了基础信息。另外,本研究还揭示Gch1在脊椎动物中的保守性,为研究其他观赏鱼类的体色变化机制提供借鉴。
The pterin metabolism pathway in Danio rerio regulates pteridine synthesis, while GTP cyclohydrolase 1 (Gch1) is the rate-limiting enzyme in this metabolic pathway. Koi (Cyprinus carpio var.koi) is a widely cultured ornamental fish with a variety of body color combinations. In order to study the function and conservation of Gch1 gene in Koi carp and its expression pattern in different body colors, we assembled a high-throughput transcriptome data from Cyprinus carpio and amplified the full-length cDNA sequence of Koi Gch1 Gen Bank Accession Number: KP056544). The gene encodes a 251 amino acid protein. Domain analysis revealed that the protein contains the GTPcyclohydrolase I domain. Gene Ontology annotation found that the protein has hydrolase activity molecular function, and is involved in intracellular nitrogen-containing compound metabolism and intracellular amino acid metabolism. The homology of multi-species Gch1 comparison found that the gene is more conservative. The adaptive evolution analysis showed that the ratio of the number of nonsynonymous substitutions per nonsynonymous site (Ka) to the number of synonymous substitutions per synonymous site (Ks) was 0.06 , Indicating that the gene in the evolution of a strong negative selection pressure. The results showed that Gch1 was involved in the pathway of pteridine metabolism; Gch1 expression in erythrocytes was significantly higher than that in white skin (P <0.05), suggesting that high expression of Gch1 may lead to body color turning red. This study, for the first time, elucidates the difference of Gch1 expression between red and white body color of Koi carp, which provides the basic information for further study on the mechanism of Gch1 in other body color changes of Koi carp. In addition, the study also revealed that Gch1 is conserved in vertebrates, providing a reference for studying the mechanism of body color changes in other ornamental fish.