Regional R&D Training Center for Insect Biotechnology (RCIB), Department of Biotechnology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand.
Sci Rep. 2020 Oct 21;10(1):17938. doi: 10.1038/s41598-020-74856-6.
Sex determination in tephritid fruit flies involves a signaling cascade of alternatively spliced genes. The Transformer (TRA) and Transformer-2 (TRA-2) complex establishes an autoregulatory loop switching sex-specific splicing of tra pre-mRNA in females. The TRA/TRA-2 complex also regulates the sex-specific splicing of downstream effector genes, doublesex (dsx) and fruitless (fru). In Ceratitis capitata, a Maleness-on the-Y (MoY) gene modulates sex-specifically spliced Cctra pre-mRNA and results in the breakdown of the Cctra autoregulatory loop in males. In this study, the tra-2 and fru genes were characterised in two key pests, Bactrocera dorsalis and B. correcta. The tra-2 genes showed high degrees of conservation among tephritids. The complex gene organisation for each of Bdfru and Bcfru were identified. There are sex-specific and non sex-specific transcripts generated by alternative promoters as found in Drosophila melanogaster and other insects. RNAi knockdown of Bdtra transcripts showed that BdTRA controls the sex-specific splicing of Bddsx and Bdfru pre-mRNAs. Developmental expression analysis shows that multiple splice variants of Bdtra and Bctra RNAs are present before and during cellular blastoderm formation and that the mature sex-specific variants become fixed later in embryogenesis. Furthermore, the Bddsx splice variants are found in early embryos at the beginning of gastulation, but Bdfru does not appear until the larval stage. We proposed that the zygotic tra loop is initiated in both female and male embryos before becoming automatised or abolished by MoY, respectively.
在果蝇中，性别的确定涉及到一个选择性剪接基因的信号级联。Transformer（TRA）和Transformer-2（TRA-2）复合物建立了一个自调节回路，在雌性中切换 tra 前体 mRNA 的性别特异性剪接。TRA/TRA-2 复合物还调节下游效应基因 doublesex（dsx）和 fruitless（fru）的性别特异性剪接。在 Ceratitis capitata 中，一个 Y 染色体上的雄性决定基因（MoY）调节性别特异性剪接的 Cctra 前体 mRNA，并导致 Cctra 自我调节回路在雄性中崩溃。在这项研究中，tra-2 和 fru 基因在两种关键害虫，Bactrocera dorsalis 和 B. correcta 中得到了表征。tra-2 基因在果蝇中高度保守。每个 Bdfru 和 Bcfru 的复合物基因组织被确定。存在由替代启动子产生的性别特异性和非性别特异性转录本，如在 Drosophila melanogaster 和其他昆虫中发现的。Bdtra 转录本的 RNAi 敲低表明 BdTRA 控制 Bddsx 和 Bdfru 前体 mRNA 的性别特异性剪接。发育表达分析表明，Bdtra 和 Bctra RNA 的多个剪接变体在细胞胚泡形成之前和期间存在，并且成熟的性别特异性变体在胚胎发生后期固定。此外，在开始原肠胚形成时，早期胚胎中发现了 Bddsx 的剪接变体，但直到幼虫阶段才发现 Bdfru。我们提出，在雌性和雄性胚胎中，合子 tra 环在分别被 MoY 自动或废除之前被启动。
