Cross kingdom analysis of natural variation in meiosis in yeast and plant accessions

In sexually reproducing organisms, crossing over during meiosis ensures that offspring are not identical to their parents. Genetic exchange provides novel allelic gene combinations that can be selected by evolution based on fitness. A large population of Arabidopsis ecotypes and yeast isolates have been collected and sequenced from different ecological niches. Meiotic recombination genes from these strains exhibit sequence divergence that has originated either by genetic drift or through selection due to environmental pressures. Preliminary data has shown that divergence of such strains becomes particularly important in hybrids where the sequence divergence inhibits proper recombination. Recombination rates vary across the genome and also vary between individuals and populations. Such variation can have impact on fertility.

Among different populations of the yeast Saccharomyces cerevisiae, recombination rates and fertility are similar. However, some hybrid crosses between populations exhibit significant reductions in recombination rates, and in one case a significant effect on fertility. Among ecotypes of Arabidopsis thaliana, there is variation is recombination rates. In both Arabidopsis and yeast, there is genetic variation in the known genes involved in meiotic recombination, in particular the ZMM genes, and these genes are conserved. Preliminary data indicate genetic interactions between variants are responsible for the reduced recombination in yeast while variation in some of these genes correlates with the recombination rate differences in Arabidopsis.

The comparative genomics of recombination rates between yeast and Arabidopsis will inform evolutionary biologists and ecologists about a fundamental aspect of adaptation to different niches – that is how does recombination rate and its variation affect adaptation to different niches and will also provide important information on the control of recombination rate in hybrids, both between different isolates of the same species but also between closely related species. This has potential applications in improving fertility in crops, many of which are hybrids, as well as facilitating crop improvement through introgression in breeding strategies.