Genome Architecture and Evolution of a Unichromosomal Asexual Nematode.

Journal Article (Journal Article)

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 is 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 fertilization through a truncated meiosis. As a prelude to functional studies, we demonstrate that D. pachys is amenable to experimental manipulation by RNA interference.

Full Text

Duke Authors

Cited Authors

  • Fradin, H; Kiontke, K; Zegar, C; Gutwein, M; Lucas, J; Kovtun, M; Corcoran, DL; Baugh, LR; Fitch, DHA; Piano, F; Gunsalus, KC

Published Date

  • October 2017

Published In

Volume / Issue

  • 27 / 19

Start / End Page

  • 2928 - 2939.e6

PubMed ID

  • 28943090

Pubmed Central ID

  • PMC5659720

Electronic International Standard Serial Number (EISSN)

  • 1879-0445

International Standard Serial Number (ISSN)

  • 0960-9822

Digital Object Identifier (DOI)

  • 10.1016/j.cub.2017.08.038


  • eng