Vine nitrogen status and volatile thiols and their precursors from plot to transcriptome level.

Area of Science:

• Viticulture and Oenology
• Plant Physiology
• Biochemistry

Background:

• Volatile thiols, particularly 3-sulfanylhexan-1-ol (3SH) and 4-methyl-4-sulfanylpentan-2-one (4MSP), significantly influence Sauvignon blanc wine's aroma profile.
• These thiols originate from non-volatile precursors during yeast fermentation.
• Understanding factors affecting thiol precursor levels is crucial for wine quality.

Purpose of the Study:

• To investigate the impact of vine nitrogen (N) status on 3SH and 4MSP concentrations in Sauvignon blanc wine.
• To analyze the effect of N supply on the levels of glutathionylated (Glut-3SH) and cysteinylated (Cys-3SH) precursors in grape berries and must.
• To evaluate the influence of N on the expression of key genes (VviGST3, VviGST4, VviGGT) involved in thiol precursor biosynthesis.

Main Methods:

• Field experiment manipulating vine nitrogen supply (N100 treatment vs. control).
• Quantification of volatile thiols (3SH, 4MSP) in wine.
• Measurement of thiol precursors (Glut-3SH, Cys-3SH) in grape berries and must using analytical chemistry techniques.
• RNA-sequencing (RNA-seq) for gene expression analysis in grape berries.

Main Results:

• Increased vine N supply significantly elevated 3SH content in the final wine.
• N supply led to higher Glut-3SH levels in grape berries and must, but did not affect Cys-3SH concentrations.
• No significant changes were observed in 4MSP levels or the expression of key genes VviGST3, VviGST4, and VviGGT.
• RNA-seq identified novel candidate genes potentially involved in 3SH precursor biosynthesis.

Conclusions:

• Elevated vine nitrogen status positively impacts 3SH concentration in Sauvignon blanc wine.
• This effect is mediated by increased Glut-3SH levels in grapes and must.
• RNA-seq analysis provided insights into candidate genes, including GSTs and transporters, involved in the N-stimulated biosynthesis of 3SH precursors.