Genome Architecture and Evolution of a Unichromosomal Asexual Nematode.
Genome Architecture and Evolution of a Unichromosomal Asexual Nematode.
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DOI：
10.1016/j.cub.2017.08.038
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发表时间：
2017-10-09
期刊：
影响因子：
--
通讯作者：
Gunsalus KC
中科院分区：
文献类型：
--
作者：
Fradin H;Kiontke K;Zegar C;Gutwein M;Lucas J;Kovtun M;Corcoran DL;Baugh LR;Fitch DHA;Piano F;Gunsalus KC
动物的无性繁殖虽然罕见，但在一些长寿的谱系中是主要或唯一的繁殖方式。无性生殖分支的寿命可能与通过重排基因组和减少重组的机制维持杂合性有关。因此，无性繁殖的物种提供了一个机会，深入了解分子变化，基因组结构和细胞过程之间的关系。在这里，我们报告的基因组序列的孤雌生殖线虫Diploscillopachys只有一个染色体对。我们发现，这unichromosomal架构是共享的一个长寿的无性线虫的遗传模式生物秀丽隐杆线虫密切相关的分支。对基因组组装的分析表明，单一染色体是由六条祖先染色体融合而成的，相邻区域之间存在广泛的重排。缺乏典型的线虫端粒和端粒保护编码基因。大多数区域显示出显著的杂合性;纯合性主要集中在一个区域，并归因于基因转换。细胞生物学和分子证据与减数分裂I的关键特征（包括突触和重组）的缺失一致。我们建议D. Pachys保留杂合性，并通过截短的减数分裂产生二倍体胚胎而不受精。作为功能研究的前奏，我们证明了D。Pachys适合通过RNA干扰进行实验操作。通过基因组测序，Fradin等人发现，线虫无性群体中的单个染色体是由六个祖先染色体结构域融合而成的。由于大多数基因座上的等位基因之间缺乏重组，进化出了高杂合性，这为这一无性谱系的意外长寿提供了一种解释。
Asexual reproduction in animals, though rare, is the main or exclusive mode of reproduction in some long-lived lineages. The longevity of asexual clades may be correlated with the maintenance of heterozygosity by mechanisms that rearrange genomes and reduce recombination. Asexual species thus provide an opportunity to gain insight into the relationship between molecular changes, genome architecture and cellular processes. Here, we report the genome sequence of the parthenogenetic nematode Diploscapter pachys with only one chromosome pair. We show that this unichromosomal architecture is shared by a long-lived clade of asexual nematodes closely related to the genetic model organism Caenorhabditis elegans. Analysis of the genome assembly reveals that the unitary chromosome arose through fusion of six ancestral chromosomes, with extensive rearrangement among neighboring regions. Typical nematode telomeres and telomeric protection-encoding genes are lacking. Most regions show significant heterozygosity; homozygosity is largely concentrated to one region and attributed to gene conversion. Cell-biological and molecular evidence are consistent with the absence of key features of Meiosis I, including synapsis and recombination. We propose that D. pachys preserves heterozygosity and produces diploid embryos without fertilizationthrough a truncated meiosis. As a prelude to functional studies, we demonstrate that D. pachys is amenable to experimental manipulation by RNA interference. By genome sequencing, Fradin et al. discover that the single chromosome in an asexual group of nematodes resulted from a fusion of six ancestral chromosomal domains. Due to the lack of recombination between alleles at most loci, high heterozygosity has evolved, providing one explanation for the unexpected longevity of this asexual lineage.
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影响因子：
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