3-Sulfanylhexanol Precursor Biogenesis in Grapevine Cells: The Stimulating Effect of Botrytis cinerea

Abstract

Volatile thiols, compounds that contribute strongly to the varietal aroma, are present in much higher concentrations in sweet wines than in dry wines. This positive effect, due to the presence of Botrytis cinerea on the berries, in fact results from a strong enrichment of cysteine S-conjugate precursors in botrytized berries. In the present study, a convenient model was investigated to reproduce and therefore study this phenomenon. A Vitis vinifera cell culture was used as a simple model, and we focused on S-3-(hexan-1-ol)-l-cysteine (P-3SH), the cysteinylated precursor of 3-sulfanylhexanol. We demonstrated that grapevine cells were able to produce P-3SH and that the presence of B. cinerea considerably increased the precursor level (up to 1000-fold). This positive result was determined to be due to metabolites secreted by the fungus. These molecules were temperature sensitive, unstable over time, and their production was activated in the presence of grapevine cells. Moreover, part of the pathway leading to P-3SH was deciphered: it was directly derived from the cleavage of S-3-(hexan-1-ol)-l-glutathione, which itself was generated after a conjugation of glutathione on (E)-2-hexenal.

A comprehensive review on Sauvignon blanc aroma with a focus on certain positive volatile thiols

“…When tested in a cell culture medium, the combination of the plant cells, B. cinerea and Glut-3MH resulted in a 250-fold higher increase in Cys-3MH concentration when compared to the plant cells and Glut-3MH with no fungus infection (Thibon et al, 2011). A decrease in concentration was observed in the continued presence of the fungus.…”

“…This reaction could be induced by the grape berry enzymes (endogenous) or the grape microflora enzymes (exogenous). Work done by Thibon et al (2011) has in fact shown increased Cys-3MH concentrations in overripe fruit infected with the B. cinerea fungus. Coetzee (2011) investigated the effect of oxidation of Sauvignon blanc juice prior to fermentation in the presence of moderate concentrations of SO 2 .…”

“…The pathway involved was confirmed when (E)-2-hexenal and glutathione were added to an induction medium containing grapevine cells and infected with B. cinerea leading to a considerable increase in Cys-3MH concentration compared to the control (Thibon et al, 2011). When tested in a cell culture medium, the combination of the plant cells, B. cinerea and Glut-3MH resulted in a 250-fold higher increase in Cys-3MH concentration when compared to the plant cells and Glut-3MH with no fungus infection (Thibon et al, 2011).…”

“…Wines obtained from botrytised grapes have been found to contain significant amounts of especially 3MH as well as other volatile thiols such as 3-mercaptopentan-1-ol (3MP) and 3-mercaptoheptan-1-ol (3MHp) (Bailly, Jerkovic, Merchand-Brynaert, & Collin, 2006;Bailly, Jerkovic, Meurée, Timmermans, & Collin, 2009;Sarrazin et al, 2007;Thibon, Cluzeet, Mérillon, Darriet, & Dubourdieu, 2011;Tominaga, Niclass, Frérot, & Dubourdieu, 2006). Although the volatile thiols have been identified as a character impacting compound in Sauvignon blanc wines, these compounds are not unique to this cultivar and have been found to contribute significantly to the aroma profiles of wines made from other varieties such as Riesling, Colombard, Semillon, Cabernet Sauvignon and Merlot (Murat et al, 2001;Tominaga, Baltenweck-Guyot, Peyrot des Gachons, & Dubourdieu, 2000).…”

Botrytized wines – current perspectives

“…The botrytization process increased the P-3SH level in grapes ~100-fold in 1 week, compared to healthy grapes. 15 The production pathway of this molecule was elucidated by Thibon et al 16 In model experiments using cell cultures, it was demonstrated that grapevine cells were able to produce P-3SH and that the presence of B. cinerea considerably increased the precursor level (up to 1,000-fold).…”