Format

Send to

Choose Destination
Curr Biol. 2017 Oct 9;27(19):2928-2939.e6. doi: 10.1016/j.cub.2017.08.038. Epub 2017 Sep 21.

Genome Architecture and Evolution of a Unichromosomal Asexual Nematode.

Author information

1
Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA.
2
Department of Biology, New York University, New York, NY 10003, USA.
3
Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA.
4
Duke Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA.
5
Department of Biology, Duke University, Durham, NC 27708, USA.
6
Department of Biology, New York University, New York, NY 10003, USA. Electronic address: david.fitch@nyu.edu.
7
Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates. Electronic address: fp1@nyu.edu.
8
Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates. Electronic address: kcg1@nyu.edu.

Abstract

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.

KEYWORDS:

Diploscapter pachys; Protorhabditis group; asexual reproduction; chromosome fusion; evolution; genome sequence; meiosis; nematode; parthenogenesis; telomere

PMID:
28943090
PMCID:
PMC5659720
DOI:
10.1016/j.cub.2017.08.038
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center