Kanamori Akira, Sugita Yosuke, Yuasa Yasufumi, Suzuki Takamasa, Kawamura Kouichi, Uno Yoshinobu, Kamimura Katsuyasu, Matsuda Yoichi, Wilson Catherine A, Amores Angel, Postlethwait John H, Suga Koushirou, Sakakura Yoshitaka
Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan.
G3 (Bethesda). 2016 Apr 7;6(4):1095-106. doi: 10.1534/g3.115.022699.
The mangrove killifish Kryptolebias marmoratus, and its close relative Kryptolebias hermaphroditus, are the only vertebrate species known to reproduce by self-fertilization due to functional ovotestis development. To improve our understanding of their genomes, we constructed a genetic map. First, a single F1 fish was made by artificial fertilization between K. marmoratus and K. hermaphroditus strains. F2 progeny were then obtained by self-fertilization of the F1 fish. We used RAD-seq to query genomic DNAs from the two parental strains, the F1 individual and 49 F2 progeny. Results identified 9904 polymorphic RAD-tags (DNA markers) that mapped to 24 linkage groups, corresponding to the haploid chromosome number of these species. The total length of the map was 1248 cM, indicating that about one recombination occurred for each of the 24 homologous chromosome pairs in each meiosis. Markers were not evenly distributed along the chromosomes: in all chromosomes, many markers (> 8% of the total markers for each chromosome) mapped to chromosome tips. Centromeres suppress recombination, and this uneven distribution is probably due to the species' acrocentric chromosomes. Mapped marker sequences were compared to genomic sequences of medaka and platyfish, the next most closely related species with sequenced genomes that are anchored to genetic maps. Results showed that each mangrove killifish chromosome corresponds to a single chromosome of both platyfish and medaka, suggesting strong conservation of chromosomes over 100 million years of evolution. Our genetic map provides a framework for the K. marmoratus/K. hermaphroditus genome sequence and an important resource for understanding the biology of hermaphroditism.
红树林鳉鱼（Kryptolebias marmoratus）及其近亲雌雄同体红树林鳉鱼（Kryptolebias hermaphroditus）是已知的仅有的因功能性雌雄同体性腺发育而通过自体受精进行繁殖的脊椎动物物种。为了增进我们对它们基因组的了解，我们构建了一张遗传图谱。首先，通过红树林鳉鱼和雌雄同体红树林鳉鱼品系之间的人工授精培育出一条单一的F1代鱼。然后，通过F1代鱼的自体受精获得F2代后代。我们使用简化基因组测序（RAD-seq）来查询两个亲本品系、F1代个体和49个F2代后代的基因组DNA。结果鉴定出9904个多态性RAD标签（DNA标记），这些标记映射到24个连锁群，与这些物种的单倍体染色体数目相对应。图谱的总长度为1248厘摩（cM），这表明在每个减数分裂过程中，24对同源染色体中的每一对大约发生一次重组。标记在染色体上并非均匀分布：在所有染色体中，许多标记（每条染色体总标记数的>8%）映射到染色体末端。着丝粒抑制重组，这种不均匀分布可能是由于该物种的近端着丝粒染色体所致。将映射的标记序列与青鳉和剑尾鱼的基因组序列进行比较，这是接下来与已测序基因组且已锚定到遗传图谱的关系最密切的物种。结果表明，每条红树林鳉鱼染色体对应于剑尾鱼和青鳉的一条单一染色体，这表明在超过1亿年的进化过程中染色体具有很强的保守性。我们的遗传图谱为红树林鳉鱼/雌雄同体红树林鳉鱼的基因组序列提供了一个框架，也是理解雌雄同体生物学的重要资源。
