Polyploidy and adaptation interplay in Neobatrachus frogs

Whole genome duplications (WGDs) double the amount of DNA and chromosomes in the organism, which becomes polyploid. From one hand, polyploidy plays important role in evolution, because it provides a backup genetic material and allows to increase genetic novelty. From the other hand, polyploids have to adapt their cellular machinery to the double amount of chromosomes, especially during meiotic cell division the process of gamete formation in sexual reproduction. Establishment of new combination of alleles by homologous recombination is one of the main characteristics of meiosis. In the newly formed autotetraploids, DNA crossovers occur randomly between each of the four copies, compromising regular chromosomal segregation. However, the existence of stable bisexual polyploids in nature proves that adaptation to such meiosis challenges is possible. The majority of such natural polyploids are plants. Simply reduction of the number of DNA crossovers to one between all four chromosomal copies improved the chances for successful meiosis in plants, and genes regulating such process were shown to be under selection. Here, I aim to understand whether such a mechanism to secure proper chromosomal segregation is universal or whether polyploid plants and animals use alternative ways. WGDs in animals are usually lethal or lead to severe conditions. Few recent WGDs have been described in animals, they occur rarely and usually such animals reproduce asexually. Amphibia is the only exception among bisexually reproducing vertebrates with multiple independent occurrences of polyploidy, for example, frog genus Neobatrachus consists of 6 diploid and 4 tetraploid species, which occupy drier areas compared to the diploids and seem to originate through autopolyploidy. This project aims to unravel the adaptation mechanism to polyploidy in Neobatrachus frogs and hence to provide the first description of such adaptation in animal kingdom. Apart from that, I will be able to clarify whether polyploidy promotes adaptation to ecologically more drastic areas in Neobatrachus frogs. To achieve that, I will assemble a new genome of the Neobatrachus, annotating functions of the genes found. Next, I will compare genetic variation along the genome for diploids and tetraploids, identifying selected regions in tetraploids and potentially adaptive changes. The last stage of the proposed project will integrate the new findings in Neobatrachus together with the results obtained in plant species. Merging this knowledge will shed light on the ways of parallel evolution of adaptation to polyploidy in plant and animal kingdoms.

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