Mechanisms of Metabolic Adaptation in Wine Yeasts: Role of Gln3 Transcription Factor

Aroa Ferrer-Pinós,Emilia Matallana,Agustín Aranda,Víctor Garrigós

doi:10.3390/fermentation7030181

Aroa Ferrer-Pinós, Emilia Matallana + Show 2 more

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https://doi.org/10.3390/fermentation7030181

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Abstract

Wine strains of Saccharomyces cerevisiae have to adapt their metabolism to the changing conditions during their biotechnological use, from the aerobic growth in sucrose-rich molasses for biomass propagation to the anaerobic fermentation of monosaccharides of grape juice during winemaking. Yeast have molecular mechanisms that favor the use of preferred carbon and nitrogen sources to achieve such adaptation. By using specific inhibitors, it was determined that commercial strains offer a wide variety of glucose repression profiles. Transcription factor Gln3 has been involved in glucose and nitrogen repression. Deletion of GLN3 in two commercial wine strains produced different mutant phenotypes and only one of them displayed higher glucose repression and was unable to grow using a respiratory carbon source. Therefore, the role of this transcription factor contributes to the variety of phenotypic behaviors seen in wine strains. This variability is also reflected in the impact of GLN3 deletion in fermentation, although the mutants are always more tolerant to inhibition of the nutrient signaling complex TORC1 by rapamycin, both in laboratory medium and in grape juice fermentation. Therefore, most aspects of nitrogen catabolite repression controlled by TORC1 are conserved in winemaking conditions.

Highlights

Saccharomyces cerevisiae is the yeast with the most biotechnological interest due to its strong fermentative metabolism and the ability to adapt efficiently to harsh and changing environments [1]
Snf1 kinase is activated by phosphorylation, increasing the functions involved in gluconeogenesis and respiration, making possible the use of other carbon sources like galactose, glycerol, or the ethanol produced by fermentation, that is consumed by a glucose-repressed isoform of alcohol dehydrogenase, ADH2 [10]
We have found that deletion of GLN3 in a haploid wine yeast has an impact in fermentation quite similar to SNF1 deletion, so those pathways may be related and indicates the relevance of this transcription factor during fermentation of grape juice

Summary

Introduction

Saccharomyces cerevisiae is the yeast with the most biotechnological interest due to its strong fermentative metabolism and the ability to adapt efficiently to harsh and changing environments [1]. Short term Crabtree effect is caused by the inability of mitochondria to deal with a strong glycolytic flux This metabolic adaptation is a good approach to ferment sugars quickly, producing high ethanol that inhibits growth of less tolerant microorganisms present in grape juice [6]. Snf kinase is activated by phosphorylation, increasing the functions involved in gluconeogenesis and respiration, making possible the use of other carbon sources like galactose, glycerol, or the ethanol produced by fermentation, that is consumed by a glucose-repressed isoform of alcohol dehydrogenase, ADH2 [10]. The activation of genes involved in the metabolism of non-preferred nitrogen sources relies upon the GATA transcription factors Gln and Gat.

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