Montchamp-Moreau C
Laboratoire Evolution, Génomes et Spéciation, CNRS UPR9034, 91198 Gif-sur-Yvette cedex, France.
Biochem Soc Trans. 2006 Aug;34(Pt 4):562-5. doi: 10.1042/BST0340562.
The sex-ratio trait, reported in a dozen Drosophila species, is a type of naturally occurring meiotic drive in which the driving elements are located on the X chromosome. Typically, as the result of a shortage of Y-bearing spermatozoa, males carrying a sex-ratio X chromosome produce a large excess of female offspring. The presence of sex-ratio chromosomes in a species can have considerable evolutionary consequences, because they can affect individual fitness and trigger extended intragenomic conflict. Here, I present the main results of the study performed in Drosophila simulans. In this species, the loss of Y-bearing spermatozoa is related to the inability of the Y chromosome sister-chromatids to separate properly during meiosis II. Fine genetic mapping has shown that the primary sex-ratio locus on the X chromosome contains two distorter elements acting synergistically, both of which are required for drive expression. One element has been genetically mapped to a tandem duplication. To infer the natural history of the trait, the pattern of DNA sequence polymorphism in the surrounding chromosomal region is being analysed in natural populations of D. simulans harbouring sex-ratio X chromosomes. Initial results have revealed the recent spread of a distorter allele.
在十几种果蝇物种中报道的性比性状，是一种自然发生的减数分裂驱动类型，其中驱动元件位于X染色体上。通常，由于含Y精子数量短缺，携带性比X染色体的雄性会产生大量雌性后代。一个物种中存在性比染色体可能会产生相当大的进化后果，因为它们会影响个体适应性并引发广泛的基因组内冲突。在此，我展示了在拟暗果蝇中进行的这项研究的主要结果。在这个物种中，含Y精子的缺失与Y染色体姐妹染色单体在减数分裂II期间无法正确分离有关。精细的基因定位表明，X染色体上的主要性比位点包含两个协同作用的扭曲元件，驱动表达需要这两个元件。其中一个元件已通过基因定位到一个串联重复序列。为了推断该性状的自然历史，正在对携带性比X染色体的拟暗果蝇自然种群中周围染色体区域的DNA序列多态性模式进行分析。初步结果揭示了一个扭曲等位基因的近期扩散。
