engleski

HOT SPOT RECOMBINATION POINT IN MITOCHONDRIAL GENOME OF GENUS Saccharomyces SHOWS HISTORICAL HYBRIDIZATION EVENTS

Genus Saccharomyces is composed by S. cerevisiae, S. paradoxus, S. cariocanus, S.mikatae, S. arboricolus, S. bayanus and S. pastorianus. Moreover, interspecific hybrids like S. pastorianus, hybrid between S. cerevisiae and S. bayanus and S. cerevisiae x S.kudriavzevii also are identified. The spore viability of these hybrids is low, about 1%, but they can grow by mitosis divisions (clonal) that is doing more complicate the definition of yeast specie. In different species of the genus we can find introgression, recombination and horizontal gene transfers that could missidentifie these yeasts. We show and example where the wrong selection of a gene can drive us to misclassify a strain, must to reticulate events. In this study we used Cox2 gene sequence, a gene from mitochondrial genome that was often used in yeast taxonomy. This gene suffers several recombinations and we detected a hot spot recombination, which involved the neighbor gene ORF1 (maturase like protein). Cox2 and ORF1 gene from different strains of the genus Saccharomyces were amplified and we demonstrated that the phylogenetic tree is not congruent with the previous species tree. ORF1 has been lost and gain in some strains and moreover we found different recombinations between different strains along the alignment of these two genes, involving GC rich regions (GC insertions). With these results we show that to suffer recombination between different sequences the strains has been hybridized for this reason the hybridization event is a common event, althoug karyogamy is not involved and not transfer of nuclear gene is not saved in the genome, it could be show that mitochondrial organelles can be together, and selfish genes like maturases give a clue that hybridization is a frequent event. In conclusion hybridization between different species of the genus Saccharomyces is frequent and could be beneficious for the genus in situations where the environmental conditions are not the best for the two parentals, in that situations a hybridization event could originate a new organism (with a chimeric genome) which could survive in the new environmental condition.

RECOMBINATION; MITOCHONDRIAL GENOME; Saccharomyces

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