Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Ancona, Italy.
Physiological Chemistry, Biocenter, University of Wuerzburg, Germany.
Genome Biol Evol. 2018 Jun 1;10(6):1430-1444. doi: 10.1093/gbe/evy101.
Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several gonad development features that differentiate tetrapods and fishes are likely to be, at least in part, related to the water-to-land transition. The collection of information from basal sarcopterygians, coelacanths, and lungfishes, is crucial to improve our understanding of the molecular evolution of pathways involved in reproductive functions, since these organisms are generally regarded as "living fossils" and as the direct ancestors of tetrapods. Here, we report for the first time the characterization of >50 genes related to sex differentiation and gametogenesis in Latimeria menadoensis and Protopterus annectens. Although the expression profiles of most genes is consistent with the intermediate position of basal sarcopterygians between actinopterygian fish and tetrapods, their phylogenetic placement and presence/absence patterns often reveal a closer affinity to the tetrapod orthologs. On the other hand, particular genes, for example, the male gonad factor gsdf (Gonadal Soma-Derived Factor), provide examples of ancestral traits shared with actinopterygians, which disappeared in the tetrapod lineage.
性别分化和生殖是维持有利基因组合和正向选择特征的关键。在脊椎动物中，一些将四足动物和鱼类区分开来的性腺发育特征可能至少部分与从水生到陆生的过渡有关。收集来自基础肉鳍鱼、腔棘鱼和肺鱼的信息对于提高我们对生殖功能相关途径的分子进化的理解至关重要，因为这些生物通常被视为“活化石”，是四足动物的直接祖先。在这里，我们首次报道了拉蒂迈鱼和非洲肺鱼中与性别分化和配子发生相关的>50 个基因的特征。尽管大多数基因的表达谱与硬骨鱼和四足动物之间的基础肉鳍鱼的中间位置一致，但它们的系统发育位置和存在/缺失模式往往显示出与四足动物同源物更密切的亲缘关系。另一方面，特定的基因，例如雄性性腺因子 gsdf（性腺体细胞衍生因子），提供了与肉鳍鱼祖先特征的例子，这些特征在四足动物谱系中消失了。
