Bernardini Federica, Galizi Roberto, Wunderlich Mariana, Taxiarchi Chrysanthi, Kranjc Nace, Kyrou Kyros, Hammond Andrew, Nolan Tony, Lawniczak Mara N K, Papathanos Philippos Aris, Crisanti Andrea, Windbichler Nikolai
Department of Life Sciences, Imperial College London, South Kensington Campus, SW7 2AZ, United Kingdom.
Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, CB10 1SA Cambridge, United Kingdom.
Genetics. 2017 Oct;207(2):729-740. doi: 10.1534/genetics.117.300221. Epub 2017 Aug 31.
Y chromosome function, structure and evolution is poorly understood in many species, including the genus of mosquitoes-an emerging model system for studying speciation that also represents the major vectors of malaria. While the Anopheline Y had previously been implicated in male mating behavior, recent data from the complex suggests that, apart from the putative primary sex-determiner, no other genes are conserved on the Y. Studying the functional basis of the evolutionary divergence of the Y chromosome in the gambiae complex is complicated by complete F1 male hybrid sterility. Here, we used an F1 × F0 crossing scheme to overcome a severe bottleneck of male hybrid incompatibilities that enabled us to experimentally purify a genetically labeled Y chromosome in an background. Whole genome sequencing (WGS) confirmed that the Y retained its original sequence content in the genomic background. In contrast to comparable experiments in , we find that the presence of a heterospecific Y chromosome has no significant effect on the expression of genes, and transcriptional differences can be explained almost exclusively as a direct consequence of transcripts arising from sequence elements present on the Y chromosome itself. We find that Y hybrids show no obvious fertility defects, and no substantial reduction in male competitiveness. Our results demonstrate that, despite their radically different structure, Y chromosomes of these two species of the gambiae complex that diverged an estimated 1.85 MYA function interchangeably, thus indicating that the Y chromosome does not harbor loci contributing to hybrid incompatibility. Therefore, Y chromosome gene flow between members of the gambiae complex is possible even at their current level of divergence. Importantly, this also suggests that malaria control interventions based on sex-distorting Y drive would be transferable, whether intentionally or contingent, between the major malaria vector species.
在包括蚊子属在内的许多物种中，Y染色体的功能、结构和进化仍知之甚少。蚊子属是一个新兴的物种形成研究模型系统，也是疟疾的主要传播媒介。虽然此前已发现按蚊Y染色体与雄性交配行为有关，但该复合体最近的数据表明，除了假定的主要性别决定基因外，Y染色体上没有其他保守基因。冈比亚复合体中Y染色体进化分歧的功能基础研究因F1雄性杂交不育而变得复杂。在这里，我们采用F1×F0杂交方案来克服雄性杂交不相容的严重瓶颈，从而能够在一个背景中通过实验纯化一条基因标记的Y染色体。全基因组测序（WGS）证实，该Y染色体在基因组背景中保留了其原始序列内容。与在其他物种中的类似实验不同，我们发现异源Y染色体的存在对基因表达没有显著影响，转录差异几乎完全可以解释为Y染色体本身存在的序列元件产生的转录本的直接结果。我们发现Y杂交种没有明显的育性缺陷，雄性竞争力也没有大幅降低。我们的结果表明，尽管这两种冈比亚复合体物种的Y染色体结构截然不同，它们在大约185万年前分化，但功能上可以互换，这表明Y染色体上不存在导致杂交不相容的基因座。因此，即使在目前的分化水平下，冈比亚复合体成员之间的Y染色体基因流动也是可能的。重要的是，这也表明基于性别扭曲Y驱动的疟疾控制干预措施，无论是有意还是偶然的，在主要疟疾传播媒介物种之间都是可转移的。
