Evolutionary journey and characterisation of a novel pan‐gene associated with beer strains of Saccharomyces cerevisiae

Abstract

The sequencing of over a thousand Saccharomyces cerevisiae genomes revealed a complex pangenome. Over one third of the discovered genes are not present in the S. cerevisiae core genome but instead are often restricted to a subset of yeast isolates and thus may be important for adaptation to specific environmental niches. We refer to these genes as “pan‐genes,” being part of the pangenome but not the core genome. Here, we describe the evolutionary journey and characterisation of a novel pan‐gene, originally named hypothetical (HYPO) open‐reading frame. Phylogenetic analysis reveals that HYPO has been predominantly retained in S. cerevisiae strains associated with brewing but has been repeatedly lost in most other fungal species during evolution. There is also evidence that HYPO was horizontally transferred at least once, from S. cerevisiae to Saccharomyces paradoxus. The phylogenetic analysis of HYPO exemplifies the complexity and intricacy of evolutionary trajectories of genes within the S. cerevisiae pangenome. To examine possible functions for Hypo, we overexpressed a HYPO‐GFP fusion protein in both S. cerevisiae and Saccharomyces pastorianus. The protein localised to the plasma membrane where it accumulated initially in distinct foci. Time‐lapse fluorescent imaging revealed that when cells are grown in wort, Hypo‐gfp fluorescence spreads throughout the membrane during cell growth. The overexpression of Hypo‐gfp in S. cerevisiae or S. pastorianus strains did not significantly alter cell growth in medium‐containing glucose, maltose, maltotriose, or wort at different concentrations.

Wild Yeast for the Future: Exploring the Use of Wild Strains for Wine and Beer Fermentation

“…For example, wine strains have a superior performance in general stress conditions (high sugar and alcohol content) compared to beer strains ( Gallone et al, 2016 ). In contrast, beer strains cover desirable and specific traits for brewing, such as maltotriose utilization, and a lack of production of undesirable off-flavors, such as 4-vinyl guaiacol ( Gallone et al, 2016 ; Krogerus et al, 2017a ; Nikulin et al, 2018 ; Vakirlis et al, 2019 ). Consequently, industrial beer strains show more notable domestication signatures than wine strains, probably because of the continuous recycling of yeast after each fermentation batch throughout the year ( Steensels et al, 2019 ).…”