An international team of geneticists refined the genome annotation of the smooth clawed frog and confirmed that these animals are allotetraploids. The results of the work are presented in the journal Nature.
Polyploidy is a multiple increase in the number of chromosomes (more than two) in a eukaryotic cell. This phenomenon is the result of interspecific or intergeneric hybridization and is more common in plants than in animals. In the latter case, polyploidy has been recorded in roundworms, fish, and a number of amphibians. For example, for the edible frog (Pelophylax kl. Esculentus) triploidy is typical due to interspecific crossing.
In a new work, scientists analyzed the evolution of the smooth clawed frog (Xenopus laevis). It is known that initially it was represented by one species, later two other species were formed from it, which then merged again into one. The authors decoded the X. laevis genome and compared it with the related diploid species Xenopus tropicalis. This made it possible to split the frog genome into two subgenomes and trace its history.
The results showed that the formation of two species from a common ancestor of the smooth clawed frog occurred about 34 million years ago. Approximately 17-18 million years ago, these species "merged" as a result of gene duplication. More than half - 56 percent - of the genes of the predecessor species have been preserved. In turn, X. laevis became an allotetraploid - an organism with two diploid sets of chromosomes.
“This allows us to split the genome of modern X. laevis into two distinct sets of chromosomes, each dating back to a unique predecessor species. Similar results were previously obtained on plants, but in this case, genome manipulation was carried out on the basis of data on surviving species. In our work, we did this for the first time with two fossil species,”said study co-author Adam Session.