# Spatial Variability of Grape Berry Maturation Program at the Molecular Level
## 3 Results and Discussion
### Spatial Variability in the Expression of Key Genes Involved in Berry Maturation
The transcriptomic analysis revealed other interesting players in key ripening metabolisms, which showed differential expression among different vigor classes. _VviMYB15_ (_Vitvi05g01733_) and _VviMYBA1_ (_Vitvi02g01019_) belong to the R2R3 MYB family of transcription factors and control different branches of the phenylpropanoid pathway during berry ripening: _VviMYB15_ regulates the biosynthesis of silbenes by controlling the expression of silbenes (STSs) [52], whereas _VviMYBA1_ targets anthocyanin-related biosynthetic genes and, therefore, controls the accumulation of these pigments [53]. Our results showed higher expression peaks for the _VviMYB15_, _VviSTS1_ (_Vitvi10g01595_), _VviSTS6_ (_Vitvi10g01599_), and _VviMYBA1_ genes in LVC at 11 DAV, which was consistent with _VviNAC60_ and _VviNAC33_ expression patterns (Figure 3). Their spatial expression variability maps at 11 DAV emphasize similarities in their intra-vineyard variation patterns, which match the variation in the vine vigor across the vineyard (Figures 1b and 4). Notably, the spatial variability map generated for _VviMYBA1_ expression was consistent with the changes in anthocyanin content in the grapes at harvest (Figure 1c), suggesting the causal relation between metabolite content and expression extent of the regulative gene. The structural gene _phytone synthase_ (_VviPSY2_, _Vitvi12g00084_) regulates a crucial step in the biosynthesis of carotenoids and has been reported to peak around veraison [54]. Consistently, our results showed _VviPSY2_ peaking at 0 DAV, higher in LVC compared to HVC. However, the highest expression variability between the blocks was observed at \(-30\) DAV when the interpolated _VviPSY2_ map was similar to the vigor class one (Figures 1b and 4). Moreover, the _VviPSY2_ gene expression map presented great similarity to the spatialization of \(\beta\)-damascenone content in berries at harvest (Figure 1c). This compound is the product of carotenoid degradation by carotenoid cleavage dioxygenase (_VviCCD4b_, _Vitvi02g01288_) [55], whose expression level was much the same across the vineyard (not shown), hinting that high \(\beta\)-damascenone in LVC is the result of greater starting concentration of carotenoids, rather than their enhanced degradation. Regardless, expression of the _VviPSY2_ gene shows potential as a predictor of intra-vineyard phenotypic variability in ripe berries, already present at very early stages of fruit development. Lipoxygenases are structural genes responsible for the metabolism of the polyunsaturated fatty acids (PUFAs), which is triggered by tissue disruption [56]. _VviLOXA_ (_Vitvi06g00158_) was identified as a switch gene and suggested to participate in berry cell enlargement, occurring during the maturation phase [57]. Our results showed divergent _VviLOXA_ expression curves across the vineyard blocks. Sharper and higher expression peaks featured HVC at 11 DAV, when the spatial expression variability map of this gene resembled the most to the vigor map, suggesting the enhancement of berry cell expansion in HVC during ripening (Figures 1b and 4). compounds are among the main products of the PUFAs degradation and were, in fact, found to be more concentrated in HVC and spatially distributed in a similar fashion to _VviLOXA_ (Figure 1c). Figure 3: Expression trends of key genes involved in berry maturation. Line graphs were created using data from each block and were plotted by days after veraison (DAV). LVC: low vigor class. MVC: medium vigor class. HVC: high vigor class.