Genome sequencing of fish from a natural population of the guppy, Poecilia reticulata, for studying sex chromosome evolution. Sex chromosome evolution in the guppy, Poecilia reticulata

This sequencing is part of an integrated programme of molecular genetic studies of sex chromosome evolution, and specifically, to use the guppy (Poecilia reticulata) to test the sexual antagonism (SA) hypothesis that suppressed recombination between X and Y chromosomes evolves to remove or mitigate inter-sexual conflict when genes with SA polymorphisms are closely linked to a sex-determining gene, i.e. located in the partially sex-linked (pseudo-autosomal) region, or PAR, of sex chromosome pairs. The guppy is a model system for studies of SA since male coloration phenotypes make males attractive to females, but also make fish conspicuous to predators (with females receiving no compensating benefit). Our study employs dense DNA-based markers to identify fully and partially sex linked sequences and study linkage disequilibrium patterns in the chromosome carrying these regions. The markers will subsequently be used in genetic mapping to determine the genomic locations of coloration genes, even in the presence of male-specific expression of some of these phenotypes. The sequences will also be used in population genetic analyses to test whether recombination rates between the male-determining region and genetic markers in the PAR differ between natural populations with low and high predation rates, and molecular evolutionary analyses to estimate the age of the guppy sex chromosome system.

本测序项目隶属于性染色体进化分子遗传学整合研究计划，具体以孔雀鱼(Poecilia reticulata)为研究对象，检验性拮抗(sexual antagonism, SA)假说：当携带性拮抗多态性的基因与性别决定基因紧密连锁（即定位于性染色体对的部分性连锁区域，又称拟常染色体区域(pseudo-autosomal region, PAR)）时，X与Y染色体间的重组抑制演化可消除或缓解性间冲突。孔雀鱼是性拮抗研究的经典模式系统，其雄性体色表型既能够增强雄性对雌性的吸引力，同时也会使雄性个体更易被捕食者察觉，而雌性无法获得对应的补偿收益。本研究使用高密度DNA分子标记，以鉴定完全性连锁与部分性连锁序列，并分析携带这些区域的染色体上的连锁不平衡(linkage disequilibrium)模式。后续将利用这些标记开展遗传作图，以确定体色基因的基因组位置，即便部分表型存在雄性特异性表达。本研究还将利用所得序列开展群体遗传学分析，以检验雄性决定区域与拟常染色体区域内的遗传标记间的重组率，在捕食压力高低不同的自然种群间是否存在差异；同时开展分子进化分析，以估算孔雀鱼性染色体系统的演化年龄。