Abstract
Industrial yeasts, economically important microorganisms, are widely used in diverse biotechnological processes including brewing, winemaking and distilling. In contrast to a well-established genome of brewer's and wine yeast strains, the comprehensive evaluation of genomic features of distillery strains is lacking. In the present study, twenty two distillery yeast strains were subjected to electrophoretic karyotyping and array-based comparative genomic hybridization (array-CGH). The strains analyzed were assigned to the Saccharomyces sensu stricto complex and grouped into four species categories: S. bayanus, S. paradoxus, S. cerevisiae and S. kudriavzevii. The genomic diversity was mainly revealed within subtelomeric regions and the losses and/or gains of fragments of chromosomes I, III, VI and IX were the most frequently observed. Statistically significant differences in the gene copy number were documented in six functional gene categories: 1) telomere maintenance via recombination, DNA helicase activity or DNA binding, 2) maltose metabolism process, glucose transmembrane transporter activity; 3) asparagine catabolism, cellular response to nitrogen starvation, localized in cell wall-bounded periplasmic space, 4) siderophore transport, 5) response to copper ion, cadmium ion binding and 6) L-iditol 2- dehydrogenase activity. The losses of YRF1 genes (Y' element ATP-dependent helicase) were accompanied by decreased level of Y' sequences and an increase in DNA double and single strand breaks, and oxidative DNA damage in the S. paradoxus group compared to the S. bayanus group. We postulate that naturally occurring diversity in the YRF1 gene copy number may promote genetic stability in the S. bayanus group of distillery yeast strains.
Highlights
The budding Saccharomyces cerevisiae is the most scientifically and industrially exploited species among the Saccharomyces sensu stricto complex as it is widely used as a model organism and in the fermentation processes such as the production of food and alcoholic beverages [1, 2]
On the basis of Pulsed-field gel electrophoresis (PFGE) separation, one can conclude that all yeasts examined belonging to the Saccharomyces sensu stricto complex [17]
Since array-CGH-based analysis revealed that the majority of genomic differences can be found in www.impactjournals.com/oncotarget subtelomeric regions of the genome of distillery strains and Y’ element ATP-dependent helicase activity may be affected in the opposite direction in the S. bayanus and S. paradoxus strain groups (Figures 3, 4 and 5), we evaluated the presence of Y’ telomeric sequences in all examined strains (Figure 6)
Summary
The budding Saccharomyces cerevisiae is the most scientifically and industrially exploited species among the Saccharomyces sensu stricto complex as it is widely used as a model organism and in the fermentation processes such as the production of food and alcoholic beverages [1, 2]. The best example of how fermentative conditions can shape the yeast genome is the acquiring SSU1-R allele-based resistance to sulfite by wine yeasts [13] This adaptation is a result of a reciprocal translocation between chromosomes VIII and XVI due to unequal crossing-over mediated by microhomology between very short sequences on the 5’ upstream regions of the SSU1 and ECM34 genes that provokes the induction of the SSU1 transporter and increases the ability of yeast cells to expulse sulfite from the cytoplasm [13]. This genetic change can be found in 50% of the wine strains, whereas it has not been observed among wild strains suggesting that the use for millennia of sulfite as a preservative in wine production could have favored its selection [14]
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