Fowler Benjamin L S, Buonaccorsi Vincent P
Department of Biology, Juniata College, 1700 Moore Street, Huntingdon, PA, 16652, USA.
Mol Ecol. 2016 May;25(10):2165-75. doi: 10.1111/mec.13594. Epub 2016 Mar 28.
Fish have evolved a variety of sex-determining (SD) systems including male heterogamy (XY), female heterogamy (ZW) and environmental SD. Little is known about SD mechanisms of Sebastes rockfishes, a highly speciose genus of importance to evolutionary and conservation biology. Here, we characterize the sex determination system in the sympatrically distributed sister species Sebastes chrysomelas and Sebastes carnatus. To identify sex-specific genotypic markers, double digest restriction site - associated DNA sequencing (ddRAD-seq) of genomic DNA from 40 sexed individuals of both species was performed. Loci were filtered for presence in all of the individuals of one sex, absence in the other sex and no heterozygosity. Of the 74 965 loci present in all males, 33 male-specific loci met the criteria in at least one species and 17 in both. Conversely, no female-specific loci were detected, together providing evidence of an XY sex determination system in both species. When aligned to a draft reference genome from Sebastes aleutianus, 26 sex-specific loci were interspersed among 1168 loci that were identical between sexes. The nascent Y chromosome averaged 5% divergence from the X chromosome and mapped to reference Sebastes genome scaffolds totalling 6.9Mbp in length. These scaffolds aligned to a single chromosome in three model fish genomes. Read coverage differences were also detected between sex-specific and autosomal loci. A PCR-RFLP assay validated the bioinformatic results and correctly identified sex of five additional individuals of known sex. A sex-determining gene in other teleosts gonadal soma-derived factor (gsdf) was present in the model fish chromosomes that spanned our sex-specific markers.
鱼类已经进化出多种性别决定（SD）系统，包括雄性异配（XY）、雌性异配（ZW）和环境性别决定。对于岩鱼属（Sebastes）的性别决定机制知之甚少，该属种类繁多，对进化生物学和保护生物学具有重要意义。在这里，我们描述了同域分布的姐妹物种红背岩鱼（Sebastes chrysomelas）和多棘岩鱼（Sebastes carnatus）的性别决定系统。为了鉴定性别特异性基因型标记，对这两个物种的40个已鉴定性别的个体的基因组DNA进行了双酶切限制性位点关联DNA测序（ddRAD-seq）。对位点进行筛选，要求在一种性别的所有个体中存在，在另一种性别中不存在且无杂合性。在所有雄性中存在的74965个位点中，有33个雄性特异性位点至少在一个物种中符合标准，17个在两个物种中都符合标准。相反，未检测到雌性特异性位点，共同证明了这两个物种都存在XY性别决定系统。当与阿留申岩鱼（Sebastes aleutianus）的参考基因组草图比对时，26个性别特异性位点散布在1168个两性相同的位点之间。新生的Y染色体与X染色体平均有5%的差异，映射到参考岩鱼基因组支架上，总长度为6.9Mbp。这些支架在三个模式鱼类基因组中与一条单一染色体比对。在性别特异性位点和常染色体位点之间也检测到了读取覆盖差异。PCR-RFLP分析验证了生物信息学结果，并正确鉴定了另外五个已知性别的个体的性别。其他硬骨鱼性腺体细胞衍生因子（gsdf）中的一个性别决定基因存在于跨越我们性别特异性标记的模式鱼类染色体中。
