Sutherland Ben J G, Rico Ciro, Audet Céline, Bernatchez Louis
Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec G1V 0A6, Canada
School of Marine Studies, Molecular Diagnostics Laboratory, University of the South Pacific, Suva, Fiji.
G3 (Bethesda). 2017 Aug 7;7(8):2749-2762. doi: 10.1534/g3.117.040915.
Whole-genome duplication (WGD) can have large impacts on genome evolution, and much remains unknown about these impacts. This includes the mechanisms of coping with a duplicated sex determination system and whether this has an impact on increasing the diversity of sex determination mechanisms. Other impacts include sexual conflict, where alleles having different optimums in each sex can result in sequestration of genes into nonrecombining sex chromosomes. Sex chromosome development itself may involve sex-specific recombination rate (, heterochiasmy), which is also poorly understood. The family Salmonidae is a model system for these phenomena, having undergone autotetraploidization and subsequent rediploidization in most of the genome at the base of the lineage. The salmonid master sex determining gene is known, and many species have nonhomologous sex chromosomes, putatively due to transposition of this gene. In this study, we identify the sex chromosome of Brook Charr and compare sex chromosome identities across the lineage (eight species and four genera). Although nonhomology is frequent, homologous sex chromosomes and other consistencies are present in distantly related species, indicating probable convergence on specific sex and neo-sex chromosomes. We also characterize strong heterochiasmy with 2.7-fold more crossovers in maternal than paternal haplotypes with paternal crossovers biased to chromosome ends. When considering only rediploidized chromosomes, the overall heterochiasmy trend remains, although with only 1.9-fold more recombination in the female than the male. Y chromosome crossovers are restricted to a single end of the chromosome, and this chromosome contains a large interspecific inversion, although its status between males and females remains unknown. Finally, we identify quantitative trait loci (QTL) for 21 unique growth, reproductive, and stress-related phenotypes to improve knowledge of the genetic architecture of these traits important to aquaculture and evolution.
全基因组复制（WGD）会对基因组进化产生重大影响，而关于这些影响仍有许多未知之处。这包括应对复制的性别决定系统的机制，以及这是否对增加性别决定机制的多样性有影响。其他影响包括性冲突，即每个性别中具有不同最优值的等位基因可能导致基因隔离到非重组性染色体中。性染色体的发育本身可能涉及性别特异性重组率（即异配交换），这也了解甚少。鲑科是研究这些现象的模型系统，在其谱系基部，基因组的大部分经历了同源四倍体化及随后的再二倍体化。鲑科的主性别决定基因已为人所知，许多物种具有非同源性染色体，推测是由于该基因的转座。在本研究中，我们确定了溪红点鲑的性染色体，并比较了整个谱系（八个物种和四个属）的性染色体特征。尽管非同源性很常见，但在远缘物种中存在同源性染色体和其他一致性，这表明可能在特定的性染色体和新性染色体上发生了趋同。我们还发现了强烈的异配交换现象，母本单倍型的交叉数比父本单倍型多2.7倍，且父本交叉偏向于染色体末端。仅考虑再二倍体化的染色体时，总体异配交换趋势仍然存在，尽管雌性的重组率仅比雄性多了1.9倍。Y染色体的交叉仅限于染色体的一端，并且该染色体包含一个大的种间倒位，尽管其在雄性和雌性之间的状态尚不清楚。最后，我们确定了21种独特的生长、繁殖和应激相关表型的数量性状位点（QTL），以增进对这些对水产养殖和进化很重要的性状的遗传结构的了解。
