Long-term persistence of supernumerary B chromosomes in multiple species of Astyanax fish

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Data

2021-12-01

Autores

Silva, Duílio Mazzoni Zerbinato de Andrade [UNESP]
Ruiz-Ruano, Francisco J.
Utsunomia, Ricardo [UNESP]
Martín-Peciña, María
Castro, Jonathan Pena
Freire, Paula Paccielli [UNESP]
Carvalho, Robson Francisco [UNESP]
Hashimoto, Diogo T. [UNESP]
Suh, Alexander
Oliveira, Claudio [UNESP]

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Resumo

Background: Eukaryote genomes frequently harbor supernumerary B chromosomes in addition to the “standard” A chromosome set. B chromosomes are thought to arise as byproducts of genome rearrangements and have mostly been considered intraspecific oddities. However, their evolutionary transcendence beyond species level has remained untested. Results: Here we reveal that the large metacentric B chromosomes reported in several fish species of the genus Astyanax arose in a common ancestor at least 4 million years ago. We generated transcriptomes of A. scabripinnis and A. paranae 0B and 1B individuals and used these assemblies as a reference for mapping all gDNA and RNA libraries to quantify coverage differences between B-lacking and B-carrying genomes. We show that the B chromosomes of A. scabripinnis and A. paranae share 19 protein-coding genes, of which 14 and 11 were also present in the B chromosomes of A. bockmanni and A. fasciatus, respectively. Our search for B-specific single-nucleotide polymorphisms (SNPs) identified the presence of B-derived transcripts in B-carrying ovaries, 80% of which belonged to nobox, a gene involved in oogenesis regulation. Importantly, the B chromosome nobox paralog is expressed > 30× more than the A chromosome paralog. This indicates that the normal regulation of this gene is altered in B-carrying females, which could potentially facilitate B inheritance at higher rates than Mendelian law prediction. Conclusions: Taken together, our results demonstrate the long-term survival of B chromosomes despite their lack of regular pairing and segregation during meiosis and that they can endure episodes of population divergence leading to species formation.

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Astyanax, B chromosomes, Evolution, Genomics, Transcriptomics

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BMC Biology, v. 19, n. 1, 2021.