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- Title
The X chromosome of the German cockroach, Blattella germanica, is homologous to a fly X chromosome despite 400 million years divergence.
- Authors
Meisel, Richard P.; Delclos, Pablo J.; Wexler, Judith R.
- Abstract
Background: Sex chromosome evolution is a dynamic process that can proceed at varying rates across lineages. For example, different chromosomes can be sex-linked between closely related species, whereas other sex chromosomes have been conserved for > 100 million years. Cases of long-term sex chromosome conservation could be informative of factors that constrain sex chromosome evolution. Cytological similarities between the X chromosomes of the German cockroach (Blattella germanica) and most flies suggest that they may be homologous—possibly representing an extreme case of long-term conservation. Results: To test the hypothesis that the cockroach and fly X chromosomes are homologous, we analyzed whole-genome sequence data from cockroaches. We found evidence in both sequencing coverage and heterozygosity that a significant excess of the same genes are on both the cockroach and fly X chromosomes. We also present evidence that the candidate X-linked cockroach genes may be dosage compensated in hemizygous males. Consistent with this hypothesis, three regulators of transcription and chromatin on the fly X chromosome are conserved in the cockroach genome. Conclusions: Our results support our hypothesis that the German cockroach shares the same X chromosome as most flies. This may represent the convergent evolution of the X chromosome in the lineages leading to cockroaches and flies. Alternatively, the common ancestor of most insects may have had an X chromosome that resembled the extant cockroach and fly X. Cockroaches and flies diverged ∼ 400 million years ago, which would be the longest documented conservation of a sex chromosome. Cockroaches and flies have different mechanisms of sex determination, raising the possibility that the X chromosome was conserved despite the evolution of the sex determination pathway.
- Subjects
BLATTELLA germanica; X chromosome; SEX chromosomes; HOMOLOGOUS chromosomes; CONVERGENT evolution; COCKROACHES
- Publication
BMC Biology, 2019, Vol 17, Issue 1, pN.PAG
- ISSN
1741-7007
- Publication type
Article
- DOI
10.1186/s12915-019-0721-x