Natural allelic variations ofSaccharomyces cerevisiaeimpact stuck fermentation due to the combined effect of ethanol and temperature; a QTL-mapping study

Abstract

1 fermentation due to the combined effect of ethanol and temperature; a QTL-2 mapping study. Abstract 6 5Background: Fermentation completion is a major prerequisite in many industrial processes 6 6 involving the bakery yeast Saccharomyces cerevisiae. Stuck fermentations can be due to the 6 7 combination of many environmental stresses. Among them high temperature and ethanol content 6 8 are particularly deleterious especially in bioethanol and red wine production. Although the genetic 6 9 causes of temperature and/or ethanol tolerance were widely investigated in laboratory conditions, 7 0 few studies investigated natural genetic variations related to stuck fermentations in high gravity 7 1 matrixes. 2Results: In this study, three QTLs linked to stuck fermentation in winemaking conditions were 7 3 identified by using a selective genotyping strategy carried out on a backcrossed population. The 7 4 precision of mapping allows the identification of two causative genes VHS1 and OYE2 characterized 7 5 by stop-codon insertion. The phenotypic effect of these allelic variations was validated by Reciprocal 7 6Hemyzygous Assay in high gravity fermentations (>240 g/L of sugar) carried out at high 7 7temperatures (>28°C). Phenotypes impacted were related to the late stage of alcoholic fermentation 7 8 during the stationary growth phase of yeast. 7 9 Conclusions: The genes identified are related to molecular functions such as Programed Cell 8 0 Death, ROS metabolism and respire-fermentative switch and were never related to fermentation 8 1 efficiency. Our findings open new avenues for better understanding yeast resistance mechanisms 8 2 involved in high gravity fermentations. 8 3 8 4 8 5 3

Quantitative Trait Nucleotides Impacting the Technological Performances of Industrial Saccharomyces cerevisiae Strains

“…In a recent study, two genes, OYE2 and VHS1 , impacting the fermentation rate at high temperature were identified in a winemaking context (Marullo et al, 2019). In both cases, an SNP was generating a codon-stop insertion impairing the completion of the fermentation above 30°C.…”

“…Although easy to identify, these loss-of-function alleles are scarcely relevant since they negatively impact the phenotype of interest. This is, for instance, the case of the OYE2 Ser77sf , ASP1 D142H , and ABZ1 S288c alleles that drastically reduce fermentation performances in an enological context (Marullo et al, 2007a; Ambroset et al, 2011; Marullo et al, 2019). As a consequence, the opposite alleles that were defined as favorable have a very low impact since they are present in most of the other genetic backgrounds.…”

“…As a consequence, the opposite alleles that were defined as favorable have a very low impact since they are present in most of the other genetic backgrounds. To overcome this problem, different approaches were used for identifying minor QTLs (Brem et al, 2005; Sinha et al, 2008; Yang et al, 2013; Holt et al, 2018; Marullo et al, 2019). The segregation of the most impacting loci is eliminated from the segregants by its deletion in the hybrid, by selecting only a part of the segregants for linkage analysis or by generating new segregants with a targeted backcross.…”