Differences in homologous recombination and maintenance of heteropolyploidy between Haloferax volcanii and Haloferax mediterranei

Ambika Dattani, Itai Sharon, Ella Shtifman-Segal, Shachar Robinzon, Uri Gophna, Thorsten Allers*, Neta Altman-Price*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Polyploidy, the phenomenon of having more than one copy of the genome in an organism, is common among haloarchaea. While providing short-term benefits for DNA repair, polyploidy is generally regarded as an “evolutionary trap” that by the notion of the Muller’s ratchet will inevitably conclude in the species’ decline or even extinction due to a gradual reduction in fitness. In most reported cases of polyploidy in archaea, the genetic state of the organism is considered as homoploidy i.e. all copies of the genome are identical. Here we demonstrate that while this is indeed the prevalent genetic status in the halophilic archaeon Haloferax volcanii, its close relative H. mediterranei maintains a prolonged heteroploidy state in a nonselective environment once a second allele is introduced. Moreover, a strong genetic linkage was observed between two distant loci in H. mediterranei indicating a low rate of homologous recombination while almost no such linkage was shown in H. volcanii indicating a high rate of recombination in the latter species. We suggest that H. volcanii escapes Muller’s ratchet by means of an effective chromosome-equalizing gene-conversion mechanism facilitated by highly active homologous recombination, whereas H. mediterranei must elude the ratchet via a different, yet to be elucidated mechanism.

Original languageEnglish
Article numberjkac306
JournalG3: Genes, Genomes, Genetics
Volume13
Issue number4
DOIs
StatePublished - Apr 2023

Funding

FundersFunder number
European Research CouncilERC-AdG 787514

    Keywords

    • gene-conversion
    • haloarchaea
    • heteropolyploidy
    • homologous recombination
    • polyploidy

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