Sulfur and Adenine Metabolisms Are Linked, and Both Modulate Sulfite Resistance in Wine Yeast

Abstract

Sulfite treatment is the most common way to prevent grape must spoilage in winemaking because the yeast Saccharomyces cerevisiae is particularly resistant to this chemical. In this paper we report that sulfite resistance depends on sulfur and adenine metabolism. The amount of adenine and methionine in a chemically defined growth medium modulates sulfite resistance of wine yeasts. Mutations in the adenine biosynthetic pathway or the presence of adenine in a synthetic minimal culture medium increase sulfite resistance. The presence of methionine has the opposite effect, inducing a higher sensitivity to SO(2). The concentration of methionine, adenine, and sulfite in a synthetic grape must influences the progress of fermentation and at the transcriptional level the expression of genes involved in sulfur (MET16), adenine (ADE4), and acetaldehyde (ALD6) metabolism. Sulfite alters the pattern of expression of all these genes. This fact indicates that the response to this stress is complex and involves several metabolic pathways.

A sulphite-inducible form of the sulphite efflux gene SSU1 in a Saccharomyces cerevisiae wine yeast

“…Indeed, although SSU1 is a target of two signal-dependent stress responses [low oxygen response (Yuasa et al, 2005) and nitrosative stress response (Sarver & DeRisi, 2005)], its expression level has never been found to be affected by sulphite. Previous studies have clearly demonstrated that this gene is not regulated by sulphite in the medium nor by sulphite accumulation in the cell (Yuasa et al, 2005), and that, although SSU1 is regulated by transcriptional control, sulphite itself is not a powerful inducer of SSU1 transcription (Aranda et al, 2006). Indeed, SSU1 was not part of a set of genes identified as being upregulated by sulphite exposure (Park & Hwang, 2008).…”

“…Given that 71B has been previously described as a sulphitesensitive strain, our findings that the sulphite detoxification system is upregulated were unexpected (Aranda et al, 2006;Yuasa et al, 2004). Thus, we used real-time quantitative PCR to further investigate the expression pattern of genes involved in sulphite metabolism during alcoholic fermentation in strain 71B and in the reference wine strain EC1118 (Novo et al, 2009;Rossignol et al, 2003).…”

“…Other studies focusing on wine yeasts have observed transcriptional control of the gene by a sulphur source (Aranda et al, 2006): methionine seems to repress SSU1, especially in the presence of sulphite. Moreover, since sulphite is an intermediate of the superpathway of sulfur amino acid biosynthesis, the expression of genes involved in this pathway (such as some MET genes) has been shown to be related with sulphite detoxification and acetaldehyde production (Aranda & del Olmo, 2004;Aranda et al, 2006).…”

Surviving in the presence of sulphur dioxide: strategies developed by wine yeasts

“…Other enzymes such as ATPase, alcohol dehydrogenase and NAD + -glutamate dehydrogenase are inhibited by sulphite but it is not known if the inhibition is reversible (Maier et al 1986). The expression of ALD6 (encoding an acetaldehyde dehydrogenase) has also been shown to be altered by the presence of sulphite (Aranda et al 2006). The latter authors showed in the same study that the expression of MET16 (encoding a 3′-phosphoadenylylsulfate (PAPS) reductase, an enzyme involved in the sulphate metabolism pathway) is also strongly reduced by SO 2 .…”

“…2, HSO 3 − is an intermediary in the SAAB and can be viewed as a potential sink for excess HSO 3 − which has entered the cell. Moreover, the concentration of these amino acids downregulates the SAAB pathway (Aranda et al 2006). The concentration of methionine in particular seems to play an important role in the activation of the SAAB pathway but also in the resistance to SO 2 .…”