Zygosaccharomyces pseudobailii, another yeast interspecies hybrid that regained fertility by damaging one of its MAT loci

Abstract

Interspecies hybridization is an important evolutionary mechanism in yeasts. The genus Zygosaccharomyces in particular contains numerous hybrid strains and/or species. Here, we investigated the genome of Zygosaccharomyces strain MT15, an isolate from Maotai-flavor Chinese liquor fermentation. We found that it is an interspecies hybrid and identified it as Zygosaccharomyces pseudobailii. The Z. bailii species complex consists of three species: Z. bailii, which is not a hybrid and whose 10 Mb genome is designated ‘A’, and two hybrid species Z. parabailii (‘AB’ genome, 20 Mb) and Z. pseudobailii (‘AC’ genome, 20 Mb). The A, B and C subgenomes are all approximately 7%–10% different from one another in nucleotide sequence, and are derived from three different parental species. Despite being hybrids, Z. pseudobailii and Z. parabailii are capable of mating and sporulating. We previously showed that Z. parabailii regained fertility when one copy of its MAT locus became broken into two parts, causing the allodiploid hybrid to behave as a haploid gamete. In Z. pseudobailii, we find that a very similar process occurred after hybridization, when a deletion of 1.5 kb inactivated one of the two copies of its MAT locus. The half-sibling species Z. parabailii and Z. pseudobailii therefore went through remarkably parallel but independent steps to regain fertility after they were formed by separate interspecies hybridizations.

Meiotic effects ofMSH4copy number variation support an adaptive role for post-polyploidy gene loss

“…This advantageous return of MSH4 to singleton would illustrate the "Less-is-more Hypothesis" 2 in its polyploid variant: the "Selected Single Copy Hypothesis" 10,53 which postulates that some maladaptive effects of polyploidy might be buffered by decreasing the dosage of the genes involved. This also echoes recent findings in yeast interspecific hybrids, which regained fertility thanks to duplicate gene loss 58,59 .…”

Diversity and Postzygotic Evolution of the Mitochondrial Genome in Hybrids of Saccharomyces Species Isolated by Double Sterility Barrier

“…Neither postzygotic reproductive isolation nor mitonuclear incompatibilities are specific to Saccharomyces; both phenomena are known in other groups of fungi as well (e.g., Olson and Stenlid, 2001;Le Gac et al, 2007;De Vienne et al, 2009;Turner et al, 2011;Giordano et al, 2018;Verma et al, 2018) and the MAT loci were also implicated in the isolation of other species (e.g., Ortiz-Merino et al, 2017;Watanabe et al, 2017;Braun-Galleani et al, 2018;Bizzarri et al, 2019). However, the current knowledge on the role and the effect of mitonuclear interactions if fungal hybrids is still limited and mainly focused on virulence (e.g., Olson and Stenlid, 2001;Verma et al, 2018;Giordano et al, 2018).…”

MAT heterozygosity and the second sterility barrier in the reproductive isolation of Saccharomyces species

“…Figure 6 depicts the correlation between the sexual behaviour and the MAT genotype in the alloploid hybrids, their sterile and fertile spores (gametes). Recently MAT genes have been implicated in the evolution and sterility of certain natural Zygosaccharomyces strains whose genome structures indicated hybrid origin (Watanabe et al 2017;Ortiz-Merino et al 2017;Braun-Galleani et al 2018;Bizzarri et al 2019). These strains have complex and diverse repertoires of MAT and MAT-like (MTL) idiomorphs inherited from the partners of the ancient hybridisation events and modified later by intragenomic chimerisation events.…”

“…The role of MAT in the sterility barrier may not be confined to Saccharomyces . MAT and MTL ( MAT -like) loci were implicated in the sterility of alloploid Zygosaccharomyces strains isolated from natural substrates (Watanabe et al 2017 ; Ortiz-Merino et al 2017 ; Braun-Galleani et al 2018 ; Bizzarri et al 2019 ).…”