《环境昆虫学报》

对离腹寡毛果实蝇性别决定基因 transformer 2 (tra-2) 进行多角度的进化分析，为研究离腹寡毛果实蝇性别决定分子机制奠定基础。通过PCR结合RACE技术克隆瓜实蝇Bactrocera cucurbitae同源transformer 2 基因的cDNA全长和内含子序列，并对该基因进行序列和进化分析。克隆得到瓜实蝇 tra-2 基因cDNA全长1467 bp，开放读码框753 bp，编码250个氨基酸残基，GenBank登录号为KR056217。瓜实蝇 tra-2 基因与其他6种离腹寡毛果实蝇的基因结构相似，均包含8个外显子和7个内含子。7种离腹寡毛果实蝇与实蝇科的地中海实蝇和按实蝇、蝇科的家蝇和丽蝇科的铜绿蝇为单一起源，而果蝇Tra-2表现出明显的分异。分子进化分析结果表明 tra-2 基因核苷酸变异主要来源于同义变异，接受净化选择压力。本研究明确了瓜实蝇 tra-2 的cDNA和基因组DNA结构特征，离腹寡毛果实蝇 tra-2 蛋白高度保守，主要接受净化选择压力。

英文摘要:

This study aims to identify the evolutionary process of the sex determining gene transformer 2 by lots of molecular genetic technologies. The finds will provide basic knowledges for further understanding of the mechanism of sex determination in insects. The full-length cDNA sequence and its intronic seqences of transformer2 ofBactrocera cucurbitae were isolated by PCR and RACE technique. Meanwhile, the sequence characteristic, phylogeny and molecular evolution of transformer 2 were analyzed by using different bioinformatics softwares. The full length of the transcript of transformer 2 of B. cucurbitae was 1467 bp and the open reading frame was 753 bp in length, which encoded a polypeptide of 250 amino acids ( GenBank accession number KR056217 ). The molecular organization of this gene was similar to the other six kinds of Bactrocerafruit flies, composed of 8 exons and 7 introns. The Tra-2 protein from seven Bactrocerafruit flies was closely related to the Tra-2 from other tephritids, such as Ceratitisand Anastrepha, as well as to other dipterans such as Musca and Lucilia, showing a monophyletic origin. However, the Tra-2 protein of Drosophila showed substantial divergence. Since the nucleotide variance of transformer 2 was essentially synonymous, the Tra-2 protein pointed toward the presence of purifying selection. In this study, the genomic and cDNA stuctures of transformer 2 was identified in B. cucurbitae. Tra-2 protein of Bactrocerafruit flies are highly conserved and appears to be primarily negatively selected.

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