Correlation between Low Temperature Adaptation and Oxidative Stress in Saccharomyces cerevisiae.

Estéfani García-Ríos,Lucía Ramos-Alonso,José M Guillamón

doi:10.3389/fmicb.2016.01199

Abstract

Many factors, such as must composition, juice clarification, fermentation temperature, or inoculated yeast strain, strongly affect the alcoholic fermentation and aromatic profile of wine. As fermentation temperature is effectively controlled by the wine industry, low-temperature fermentation (10–15°C) is becoming more prevalent in order to produce white and “rosé” wines with more pronounced aromatic profiles. Elucidating the response to cold in Saccharomyces cerevisiae is of paramount importance for the selection or genetic improvement of wine strains. Previous research has shown the strong implication of oxidative stress response in adaptation to low temperature during the fermentation process. Here we aimed first to quantify the correlation between recovery after shock with different oxidants and cold, and then to detect the key genes involved in cold adaptation that belong to sulfur assimilation, peroxiredoxins, glutathione-glutaredoxins, and thioredoxins pathways. To do so, we analyzed the growth of knockouts from the EUROSCARF collection S. cerevisiae BY4743 strain at low and optimal temperatures. The growth rate of these knockouts, compared with the control, enabled us to identify the genes involved, which were also deleted and validated as key genes in the background of two commercial wine strains with a divergent phenotype in their low-temperature growth. We identified three genes, AHP1, MUP1, and URM1, whose deletion strongly impaired low-temperature growth.

Highlights

Microorganisms constantly face environmental stimuli and stresses
Sulfur assimilation induction is understood in the oxidative stress context as cysteine is a component of molecules like glutathione, glutaredoxin and thioredoxin, which were all induced in response to oxidative stress (Sha et al, 2013), while methionine acts as a reactive oxygen species (ROS) scavenger (Campbell et al, 2016). After considering all these data, this work aimed to identify the correlation between low-temperature growth and recovery after oxidative stress shock, and the detection of the key genes related to the oxidative stress response, which play an important role in the adaptation of S. cerevisiae to low temperature
In order to assess the correlation between low temperature and oxidative stress, hierarchical clustering analyses were performed using Euclidean distances with the area under the OD vs. time curve (AUC) of each growth experiment

Summary

Introduction

Microorganisms constantly face environmental stimuli and stresses. The environmental stress response in yeast is a complicated strategy in which responses to many stresses partially overlap (Gasch et al, 2000; Causton et al, 2001; Mitchell et al, 2009). Drops in ambient temperature are common in almost every ecological niche. In the yeast Saccharomyces cerevisiae, reductions in ambient temperature have widespread effects on growth and survival, which depend on the severity of stress. This is relevant for industrial yeast exploitations as several fermentations, like brewing and some wine fermentations, take place at around 12–15◦C. Fermentation at lower temperatures correlates with a fresh character and fruity notes in wines, and reduces the risk of bacterial contamination and the

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