Simultaneous Mendelian and clonal genome transmission in a sexually reproducing, all-triploid vertebrate




Stock, Matthias
Ustinova, Jana
Betto-Colliard, Caroline
Schartl, Manfred
Perrin, Nicolas
Moritz, Craig

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Royal Society of London


Meiosis in triploids faces the seemingly insuperable difficulty of dividing an odd number of chromosome sets by two. Triploid vertebrates usually circumvent this problem through either asexuality or some forms of hybridogenesis, including meiotic hybridogenesis that involve a reproductive community of different ploidy levels and genome composition. Batura toads (Bufo baturae; 3n = 33 chromosomes), however, present an all-triploid sexual reproduction. This hybrid species has two genome copies carrying a nucleolus-organizing region (NOR-) on chromosome 6, and a third copy without it (NOR+). Males only produce haploid NOR+ sperm, while ova are diploid, containing one NOR+ and one NOR- set. Here, we conduct sibship analyses with co-dominant microsatellite markers so as (i) to confirm the purely clonal and maternal transmission of the NOR- set, and (ii) to demonstrate Mendelian segregation and recombination of the NOR+ sets in both sexes. This new reproductive mode in vertebrates ('pre-equalizing hybrid meiosis') offers an ideal opportunity to study the evolution of non-recombining genomes. Elucidating the mechanisms that allow simultaneous transmission of two genomes, one of Mendelian, the other of clonal inheritance, might shed light on the general processes that regulate meiosis in vertebrates.



Keywords: microsatellite DNA; chromosome; clonal organism; evolutionary biology; genome; hybrid; ploidy; recombination; sexual reproduction; toad; animal; article; biological model; Bufonidae; chromosome NOR; cross breeding; diploidy; female; genetic recombination; Biased genome transmission; Bufo viridis subgroup; Clonal; Mendelian segregation; Recombination; Triploid vertebrate



Proceedings of the Royal Society of London Series B: Biological Sciences


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