Permpoon Rattiya, Aketarawong Nidchaya, Thanaphum Sujinda
Department of Biotechnology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand.
Genetica. 2011 Jan;139(1):113-27. doi: 10.1007/s10709-010-9508-2. Epub 2010 Oct 26.
Doublesex (dsx) is a double-switch gene at the bottom of the somatic sex-determination hierarchy which regulates sexual dimorphism in many insects. Here, Drosophila melanogaster homologues of dsx were isolated in two Bactrocera species, the oriental fruit fly, B. dorsalis, and the guava fruit fly, B. correcta. Results of RT-PCR analysis suggests that both the B. dorsalis dsx (Bd1dsx) and B. correcta dsx (Bcdsx) genes are transcribed and sex-specifically spliced in accordance with the Drosophila sex-specific splicing mechanism. The cDNA sequences shared a high degree of similarity at the nucleotide level among the Bactrocera species. Structurally conserved domains for DNA-binding and oligomerization were observed in all transcripts suggesting that their proteins function as transcriptional factors for downstream sex-specific gene expression. A purine-rich element (PRE) and four repeat elements (dsxRE) for TRA/TRA-2 binding sites were also found in the 3' untranslated regions (UTR) of both the female Bd1dsx and Bcdsx mRNAs. Notably, a putative core promoter was revealed in Bd1dsx, being probably the first dsx promoter discovered in the tephritid flies.
双性基因（dsx）是位于体细胞性别决定层级底部的一个双开关基因，它调控着许多昆虫的性别二态性。在此，在两种实蝇物种中分离出了果蝇dsx的同源物，即东方果实蝇（桔小实蝇）和番石榴实蝇。逆转录聚合酶链反应（RT-PCR）分析结果表明，桔小实蝇dsx（Bd1dsx）基因和番石榴实蝇dsx（Bcdsx）基因均按照果蝇性别特异性剪接机制进行转录和性别特异性剪接。在实蝇物种中，这些cDNA序列在核苷酸水平上具有高度相似性。在所有转录本中均观察到了用于DNA结合和寡聚化的结构保守结构域，这表明它们的蛋白质作为下游性别特异性基因表达的转录因子发挥作用。在雌性Bd1dsx和Bcdsx mRNA的3'非翻译区（UTR）中还发现了一个富含嘌呤的元件（PRE）和四个用于TRA/TRA-2结合位点的重复元件（dsxRE）。值得注意的是，在Bd1dsx中发现了一个推定的核心启动子，这可能是在实蝇科果蝇中发现的首个dsx启动子。
