Varietal Dependence of GLVs Accumulation and LOX-HPL Pathway Gene Expression in Four Vitis vinifera Wine Grapes

Abstract

Variety is one of the major factors influencing grape and wine aromatic characteristics. Green leaf volatiles (GLVs), derived from lipoxygenase-hydroperoxides lyase (LOX-HPL) pathway, are important components for the aromatic quality of grapes and wines. However, the varietal difference regarding GLVs accumulation and related gene expression are poorly studied. This work exhibited that the accumulation of various GLVs and the expression of LOX-HPL pathway genes in four Vitis vinifera wine grape cultivars: Syrah, Muscat Tchervine, Gewürztraminer and Chardonnay. The results showed a variety dependence of GLVs profile. Muscat Tchervine harvested grapes contained less C6 aldehydes and the most abundant esters, which corresponded to very low VvLOXA and VvHPL1 expression abundance as well as high VvAAT transcript in this variety. High expression level of both VvLOXA and VvHPL1 paralleled with higher level of C6 aldehydes together with higher alcohols in Syrah grape. Gewürztraminer and Chardonnay grapes had high aldehydes and alcohols as well as low esters, which were resulted from their higher expression level of VvLOXA or VvHPL1 and lower VvAAT. From these above corresponding relations, it is concluded that VvLOXA, VvHPL1 and VvAAT in the LOX-HPL pathway are targets for altering GLVs composition in the grape varieties.

Differential Expression of VvLOXA Diversifies C6 Volatile Profiles in Some Vitis vinifera Table Grape Cultivars

“…Meanwhile, the 2013 ripenedgrape cultivars possessed a higher concentration of the total C6 alcohols than those harvested in 2014. ( E )-2-hexen-1-ol appeared to be the dominant C6 alcohol in these grapes, which was different to some wine-making grapes [ 18 , 26 ]. Additionally, these table grape cultivars at the harvest contained a higher content of ( E )-2-hexen-1-ol than ( Z )-3-hexen-1-ol.…”

“…C6 volatile compounds are accumulated in grape berries along with the berry development stages, and their level in ripened grape berries determines the overall aroma [ 18 , 24 , 26 ]. In the present study, a total of 11 C6 volatiles were detected in these table grapes at harvest.…”

“…The berry maturation process of these two cultivars resulted in a decrease in its expression. A previous study has reported that VvADH1 expression was enhanced before veraison and then inhibited when wine-making grapes approached ripeness [ 26 ].…”

“…The extraction of the total RNA and the transcript analysis of the key LOX-HPL pathway genes followed a published method [ 26 , 27 ]. Briefly, a mortar was heated at 200 °C for 4 h before the extraction of the total RNA in the grapes to avoid any contamination.…”

“…Biologically, the biosynthesis of C6 volatile compounds in fruits results from oxylipin metabolism under the activity of lipoxygenase (LOX), hydroperoxide lyase (HPL), alcohol dehydrogenase (ADH), and alcohol acetyltransferase (AAT) in the LOX/HPL pathway [ 23 ]. The composition and distribution of C6 volatile compounds in grape berries is determined by grape germplasm, cultivar, climate, soil, vintage, and cultivation management [ 14 , 17 , 24 , 25 , 26 , 27 ]. For instance, it has been reported that alteration of the microclimate, such as light exposure duration and water conditions, could inhibit or stimulate the expression of the LOX/HPL-pathway-related genes, which further results in alteration of the activity of C6 volatiles’ synthesis-related enzymes.…”