## 3 Discussion  
Aromatic development in white grapes is the result of the activity of a wide range of metabolic pathways balanced by the interplay between developmental and environmental cues [1]. Several parameters play crucial roles in determining the final grape composition in terms of sugars, acidity, and the accumulation of secondary metabolites and, consequently, in wine quality. These include genetic factors, vineyard management, soil physico-chemical composition, and climatic factors. Secondary metabolites have a great impact on wine aroma, which in turn is recognized as one of the main factors in wine's quality [1; 5]. The evident impacts of climate change on grape berry aroma and composition are complex and vary depending on the specific components of the aromatic profiles [6; 7]. Maintaining suitable compositional characteristics for later transformation into wines with well-defined and recognizable sensory attributes is an urgent need for wine makers and markets, requiring the implementation of effective mitigation strategies. The adoption of naturally derived molecules to enhance the overall aroma complexity of grapes or to keep it at acceptable levels even in the presence of the negative effects of adverse climatic conditions represents an important tool for viticulturists [6; 7; 8]. The use of DYE applications on grapes has been recently proven to be an effective strategy to ensure the maintenance of secondary metabolite content. For example, in Merlot grapes, [PERSON] et al. (2021) [95] have shown that DYE treatments increased overall flavonoids and anthocyanin contents and their extractability [95]. Consistently, [PERSON] et al. (2020) [14] have reported that DYE treatments stimulated the biosynthesis of anthocyanins in the berries of Sangiovese potted plants, leading the authors to conclude that DYE may be an effective mitigation strategy to counteract the detrimental effects of high temperatures on anthocyanin biosynthesis [14]. Similarly, additional studies performed on white grapes demonstrated that the DYE application on grapes may also be effective in improving or better maintaining the aromatic precursors in Glera [96]. In Sauvignon Blanc (SB), these effects included a stimulation of GSH and of the thiol aroma precursors of 3-mercaptoethanol (3 MH) typical of Sauvignon Blanc grapes, such as cysteine- and glutathione-bound cys-3 MH and GSH-3 MH, respectively [10]. Even though [PERSON] et al. (2020) [14] have shown that in red grapes, DYE exerts its action through the upregulation of the key genes involved in the anthocyanin biosynthetic pathway (e.g., PAL (phenylalanine ammonia lyase), CHS and CHI (chalcone synthase and isomerase), and F3H (flavanone 3-hydroxylase)), the mechanisms of action of DYE are still only partially clarified [14]. In this manuscript, we have aimed at reaching a more comprehensive view of the physiological and molecular mode of action of DYE in white grapes. To this end, we have treated SB's vineyards for two consecutive years (2020 and 2021) with specific inactive dry yeast extracts. Following the application, we have characterized as comprehensively as possible the evolution of ripening, the contents of the main berry metabolites, and the transcriptional profiles. Our data confirmed previous findings suggesting that DYE did not interfere with the overall technological ripening in that, at H, acidity and total sugars showed no significant differences between treated and control samples [15]. Therefore, DYE treatments did not significantly interfere with the overall ripening process of SB grapes in the years considered. Thus, DYE action seems to depend on more specific effects on selected metabolic pathways. In fact, cys-3 MH and GSH-3 MH (the precursors strongly influencing the aromatic profile of SB's wine), terpen (nerol and geranic acid), and benzenoids (methyl salicate) increased in the berries of DYE-treated SB grapevines, in agreement with the findings of [PERSON] et al. (2016) [15].