榕小蜂两性发育关键基因 doublesex 结构及可变剪接的变异与性别分化之间的联系

In the sexual development pathway, the doublesex (dsx) gene plays an important role, as a junction of the upstream sex determination cascade, and the downstream sexual differentiation cascade. It has long been considered that despite genes in both the top and bottom parts of the sexual development are variable, the in-between gene dsx is conserved in gene structure and sex-specific splicing. Recently, studies have provided insight into the variation of dsx among different insect species, though the evolutionary history of dsx and the driving force behind the variation of dsx have not been revealed. Our preliminary study has also detected unique gene characteristics and sex-specific splicing forms of dsx in the fig wasp Ceratosolen solmsi marchali, challenging the understanding of the conservation of dsx. Because C. solmsi marchali is distinctive in sexual differentiation as it is an extreme case of sexual dimorphism, we propose that there may be a correlation between the variation of dsx of C. solmsi marchali and its extreme sexual dimorphism. Fig wasps are all chalcids that live in the Ficus (including five families), with almost half of which present extreme sexually dimorphic characteristics. Here, we will describe dsx genes of 23 fig wasp species (11 species with extreme sexual dimorphism, 9 without sexual dimorphism, and 3 with male-polymorphism). The dsx sequences will be obtained by gene cloning, and the sex-specific splicing of dsx will be examined. The evolutionary analysis of dsx in diverse fig wasp species may provide evidence on the putative correlation between the variation of dsx and its downstream sexual differentiation cascade.

在昆虫的两性发育过程中，doublesex(dsx)衔接了其上游的性别决定与下游的性别分化，起着枢纽作用。人们一直认为两性发育的两端进化速度快，而中部dsx极其保守。近期人们发现dsx在昆虫中具有一定程度的变异，但却没有找出它变异的规律，更没有发现这些变异的生物学意义。我们也在一种榕小蜂中发现了独特的dsx结构（2个OD2功能域）及剪接方式的变异。该物种具有动物界罕见的性别分化（极端雌雄异形），因此我们假设其dsx的变异可能与其极端雌雄异形的性别分化格局相关。广义的榕小蜂指所有生活在榕果内的小蜂（包括5个科），其近半数类群都具有极端雌雄异形。本项目将选取23种榕小蜂（极端雌雄异形11种、不具有极端雌雄异形9种，以及雄性多型3种），通过对dsx的扩增、性别特异可变剪接的筛查，及选择压力的分析，研究dsx在榕小蜂不同物种中的进化历程，揭示dsx的变异是否与其下游性别分化的进化格局存在关联。

Doublesex(dsx)基因在昆虫的两性发育过程中，衔接了其上游的性别决定与下游的性别分化，起着枢纽作用。在一种榕小蜂中已经发现了独特的dsx结构（2个OD2功能域）及剪接方式的变异，这极大的挑战了人们对dsx保守性的认识。本研究对极端雌雄异形、正常雌雄异形、雄性多型的榕小蜂，以及20种蚂蚁进行采集和数据搜集，最终实验获得其中4种榕小蜂和1种蚂蚁的dsx全长，完成其dsx基因性别/品级特异可变剪接的筛查。最终通过对共计35种膜翅目昆虫DMRT基因家族的进化分析，确定dsx与性别相关的种内多型（性别分化和品级分化）具有一定的关联性。

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