Category Archives: recombination

A lot can happen after a few drinks: Saccharomyces hybridization

We may have to reevaluate whether Saccharomyces cerevisiae alone is the species used to brew beer.  A paper from Gonzalez et al describes results from PCRRFLP comparison of 24 brewing strains identifies evidence for S. cerevisiae x S. kudriavzevii hybrids.  Although this hybridization is not unprecedented, most seem to be related to cultivated brewing or fermentation strains.  It seems that the hybrids are better able to cope with the stress associated with fermentation process.

Sacch tree

It seems these would also be a great test system for more whole genome sequencing or at least more polymorphism comparisons to try and determine the proportion of the genome that comes from different parents and estimate timing and frequency of hybridization.  It seems possible that the hybridizations are occurring multiple times in nature so are the same regions from each parental genome kept in the hybrid offspring that are selected for fitness under fermentation stress?

Gonzalez, S.S., Barrio, E., Querol, A. (2008). Molecular Characterization of New Natural Hybrids of Saccharomyces cerevisiae and S. kudriavzevii in Brewing . Applied and Environmental Microbiology, 74(8), 2314-2320. DOI: 10.1128/AEM.01867-07

Sex in fungi: MAT locus cloned from a Zygomycete

On the cover of this week’s Nature is a picture of Phycomyces blakesleeanus Nature Coverhighlighting the discovery of the MAT locus in this Zygomycete fungus from Alex Idnurm and Joe Heitman and colleagues. While it was previously known that Zygomycetes (the Orange lineage represented by R. oryzae in the tree below) mate, the specific locus has until now, never been discovered. The authors in this study identified the MAT locus through a sequence search looking for HMG-box genes knowing that these are found the Mating Type locus in Basidiomycetes and Ascomycetes. They confirmed the identity through a through set of experiments that included PCR, sequencing and crosses of (+) and (-) strains of P. blakesleeanus, and Southern blots.

Continue reading Sex in fungi: MAT locus cloned from a Zygomycete

Yeast keeps to itself

Cliff Zeyl and Sally Otto present a nice review on research from the Kruglyak lab regarding evidence that Saccharomyces is primarily a selfer in nature as it outbreeds very infrequently (once in 50,000 generations). The implications of this work has relevance on the importance of sexual reproduction and recombination in natural populations.