A research group at Hokkaido University has clarified the mechanism by which a field hybrid of the genus Hexagrammos, which reproduces half-clone, refreshes the genome by incorporating a recombinant generation and prolongs line life while acquiring genetic diversity.
Among the genus Hexagrammos, which is a representative rocky fish in Hokkaido, the habitat of hybrids with the genomes of Sujiainame and Kujime has recently been confirmed.All of these hybrids are female and use the paternal (whale) genome until they are fertilized to adulthood, but disappear during oogenesis, and only the maternal (sujiainame) genome is clonally inherited by the offspring.
In this way, semi-clones and cloned organisms that transmit only the genome derived from the mother species to their offspring are at risk of self-destruction due to the accumulation of malignant mutations and annihilation due to lack of diversity.However, it is said that actual semi-cloned organisms have survived for at least hundreds of thousands of generations, suggesting the existence of some mechanism for updating the genome.
In this study, we investigated the mode of inheritance using eggs collected from territories of Sujiainame and Kujime, and found that hybrids were mated at almost the same rate as both parent species.When mated with a paternal species (Kujime), it becomes half-clone reproduction, but when mated with a mother species (Sujiainame), the genome of the Sujiainame becomes two sets, and the "recombinant generation" (sexual reproduction generation) undergoes normal meiosis. ).Since the streaks and whales have a strong reproductive isolation mechanism and rarely cross, the half-clone genome is refreshed during the alternation of generations in the recombinant generation.After reducing harmful mutations and restoring genetic diversity, half-clone generations have been accidentally crossed due to volcanic eruptions and global warming on a geohistorical scale of hundreds or thousands of years. It will be resumed.
In fact, multiple haplotypes have been observed in semi-cloned hybrids, suggesting that recrossing occurred multiple times.This research can be said to be the world's first achievement that clarified the mechanism by which a semi-cloned organism has a recombinant generation and resets and perpetuates the cloned genome.
Paper information:[Evolution] Unisexual hybrids break through an evolutionary dead end by two-way backcrossing
