Biosynthesis of sesquiterpenes in grape berry exocarp of Vitis vinifera L.: Evidence for a transport of farnesyl diphosphate precursors from plastids to the cytosol

Abstract

The participation of the mevalonic acid (MVA) and 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol-4-phosphate (DOXP/MEP) pathways in sesquiterpene biosynthesis of grape berries was investigated. There is an increasing interest in this class of terpenoids, since the oxygenated sesquiterpene rotundone was identified as the peppery aroma impact compound in Australian Shiraz wines. To investigate precursor supply pathway utilization, in vivo feeding experiments were performed with the deuterium labeled, pathway specific, precursors [5,5-2H2]-1-deoxy-D-xylulose and [5,5-2H2]-mevalonic acid lactone. Head Space-Solid Phase Micro Extraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) analysis of the generated volatile metabolites demonstrated that de novo sesquiterpene biosynthesis is mainly located in the grape berry exocarp (skin), with no detectable activity in the mesocarp (flesh) of the Lemberger variety. Interestingly, precursors from both the (primarily) cytosolic MVA and plastidial DOXP/MEP pathways were incorporated into grape sesquiterpenes in the varieties Lemberger, Gewürztraminer and Syrah. Our labeling data provide evidence for a homogenous, cytosolic pool of precursors for sesquiterpene biosynthesis, indicating that a transport of precursors occurs mostly from plastids to the cytosol. The labeling patterns of the sesquiterpene germacrene D were in agreement with a cyclization mechanism analogous to that of a previously cloned enantioselective (R)-germacrene D synthase from Solidago canadensis. This observation was subsequently confirmed by enantioselective GC-MS analysis demonstrating the exclusive presence of (R)-germacrene D, and not the (S)-enantiomer, in grape berries.

Fortification and Elevated Alcohol Concentration Affect the Concentration of Rotundone and Volatiles in Vitis vinifera cv. Shiraz Wine

“…No obvious rotundone increase was observed in the Ts-day5 treatment, likely due to the less rotundone extraction time after wine alcohol reaches a relatively high level. Rotundone, similar to other sesquiterpenes, exists in the exocap of the grape berry (skin), rather than the mesocarp (flesh) [5,14,20]. Therefore, longer contact time between grape exocap and the fermented juice is critical for rotundone extraction.…”

“…Rotundone is responsible for the attractive "pepper" character in grape berries and wine, and is especially important for cool-climate Shiraz (Syrah) [6][7][8]. It is possible to manipulate the concentration of this compound in wine by increasing rotundone production in grape berries [8][9][10][11][12][13][14][15][16][17][18][19]. Approximately 10% of the rotundone in grape skins is extracted into the grape berries during fermentation, regardless of starting concentration, so any manipulation that increases the amount of rotundone in grapes will be reflected by an increase in wine.…”

Modeling of Dolichol Mass Spectra Isotopic Envelopes as a Tool to Monitor Isoprenoid Biosynthesis

“…Various intermediates (e.g. IPP, DMAPP, GPP, FPP, and oligoprenyl diphosphates; Hemmerlin et al, 2012;May et al, 2013) were shown to be translocated between these compartments. Moreover, a complex bidirectional transfer of precursors was postulated earlier (Skorupinska-Tudek et al, 2008) as well as in the current model (Fig.…”

Polyprenols Are Synthesized by a Plastidial cis-Prenyltransferase and Influence Photosynthetic Performance

“…This "division of labor" allows for the compartment-specific synthesis of brassinosteroids, sesquiterpenes, sterols, and ubiquinone from the cytosolic MVA pathway, while the MEP pathway provides the precursors for the synthesis of abscisic acid, carotenoids, chlorophyll, gibberellins, plastoquinone, and various mono-and diterpenes in the plastid (Lange et al, 2000;Vranová et al, 2013). In spite of this strict compartmentalization of the two pathways, the exchange of isoprenoid precursors between the plastids and cytosol is well recognized in some plant species and leads to the synthesis of "mosaic compounds" that are composed of isoprenoid intermediates derived from both the MVA and MEP pathways (Hemmerlin et al, 2003;Laule et al, 2003;Dudareva et al, 2005;Bartram et al, 2006;Skorupinska-Tudek et al, 2008;May et al, 2013;Opitz et al, 2014).…”