The Oriental fruit fly, Bactrocera dorsalis, is a highly polyphagous invasive species with a high reproductive potential. In many tropical and subtropical parts of the world it ranks as one of the major pests of fruits and vegetables. Due to its economic importance, genetic, cytogenetic, genomic and biotechnological approaches have been applied to understand its biology and to implement the Sterile Insect Technique, currently a part of area-wide control programmes against this fly. Its chromosome complement includes five pairs of autosomes and the sex chromosomes. The X and Y sex chromosomes are heteromorphic and the highly heterochromatic and degenerate Y harbours the male factor BdMoY. The characterization of the Y chromosome in this fly apart from elucidating its role as primary sex determination system, it is also of crucial importance to understand its role in male biology. The repetitive nature of the Y chromosome makes it challenging to sequence and characterise. Using Representational Difference Analysis, fluorescent in situ hybridisation on mitotic chromosomes and in silico genome resources, we show that the B. dorsalis Y chromosome harbours transcribed sequences of gyf, (typo-gyf) a homologue of the Drosophila melanogaster Gigyf gene, and of a non-LTR retrotransposon R1. Similar sequences are also transcribed on the X chromosome. Paralogues of the Gigyf gene are also present on the Y and X chromosomes of the related species B. tryoni. Another identified Y-specific repetitive sequence linked to BdMoY appears to be specific to B. dorsalis. Our random scan of the Y chromosome provides a broad picture of its general composition and represents a starting point for further applicative and evolutionary studies. The identified repetitive sequences can provide a useful Y-marking system for molecular karyotyping of single embryos. Having a robust diagnostic marker associated with BdMoY will facilitate studies on how BdMoY regulates the male sex determination cascade during the embryonic sex-determination window. The Y chromosome, despite its high degeneracy and heterochromatic nature, harbours transcribed sequences of typo-gyf that may maintain their important function in post-transcriptional mRNA regulation. That transcribed paralogous copies of Gigyf are present also on the X and that this genomic distribution is maintained also in B. tryoni raises questions on the evolution of sex chromosomes in Bactrocera and other tephritids.

中文翻译：

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东方实蝇Bactrocera dorsalis的Y染色体上转录的性别特异性标记

东方实蝇Bactrocera dorsalis是一种高度多食性入侵种，具有很高的繁殖潜力。在世界许多热带和亚热带地区，它被认为是水果和蔬菜的主要害虫之一。由于其经济重要性，已采用遗传，细胞遗传学，基因组和生物技术方法来了解其生物学并实施不育昆虫技术，这是目前针对该蝇的区域控制计划的一部分。它的染色体互补包括五对常染色体和性染色体。X和Y性染色体是异型的，高度异色和简并的Y包含雄性因子BdMoY。除了阐明其作为主要性别决定系统的作用外，此蝇中Y染色体的特征是，了解其在男性生物学中的作用也至关重要。Y染色体的重复性质使其难以测序和表征。使用代表性差异分析，有丝分裂染色体和计算机硅基因组资源上的荧光原位杂交，我们表明背叶酵母Y染色体带有gyf，（typo-gyf）果蝇果蝇Gigyf基因的同系物的转录序列。非LTR反转录转座子R1。类似的序列也被转录在X染色体上。Gigyf基因的旁系同源物也存在于相关物种B. tryoni的Y和X染色体上。链接到BdMoY的另一个已鉴定的Y特异性重复序列似乎是对B. dorsalis特异的。我们对Y染色体的随机扫描提供了其总体组成的全景，并代表了进一步的应用和进化研究的起点。鉴定出的重复序列可为单个胚胎的分子核型分析提供有用的Y标记系统。具有与BdMoY相关的强大诊断标记将有助于研究BdMoY如何在胚胎性别决定窗口期间调节男性性别决定的级联。尽管Y染色体具有高度的简并性和异色性，但它仍保留了打字错误的转录序列，可能在转录后mRNA调控中保持其重要功能。吉吉夫转录的旁系同源拷贝也出现在X轴上，并且这种基因组分布也保持在B轴上。