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•S. cerevisiae BDX and H. vineae HV6 overproduced 2-phenylethyl alcohol (2-PE) and 2-phenylethyl acetate (2-PEA), respectively.•Phe improved 2-PE and 2-PEA concentrations in pure BDX ...and HV6 cultures, respectively.•14.9 fold increment of 2-PEA and 42.0 % reduction of 2-PE in mixed fermentation.•2-PEA and 2-PE were enhanced by 52.8 % and 44.4 % by Phe, respectively.•HV6 and BDX have synergistic effect on 2-PEA in mixed fermentation.
2-Phenylethyl acetate (2-PEA) is a desired aroma compound in wine due to its honey- and flowery-like characteristics. The effects of adding l-phenylalanine (Phe) during 2-PEA production were investigated in the co-fermentation of Hanseniaspora vineae (HV6) and Saccharomyces cerevisiae BDX. BDX and HV6 strains overproduced 2-phenylethyl alcohol (2-PE) and 2-PEA, respectively. The co-fermentation of BDX and HV6 achieved a 14.9 fold increase in 2-PEA odour activity value (OAV) but a 42.0 % reduction of 2-PE OAV compared to BDX fermentation; the 2-PEA concentration was significantly higher than the sum of BDX and HV6 pure fermentations. This suggests that BDX and HV6 have synergistic effects on 2-PEA formation in mixed culture. Adding 151.6 mg/L Phe enhanced the OAV of 2-PEA by 52.8 % compared to the control. The combination of Phe addition with the co-fermentation of S. cerevisiae and H. vineae is a potential way to increase 2-PEA production and improve wine aromatic quality.
Proanthocyanidins (PAs) and anthocyanins are two vital groups of flavonoid compounds for grape berries and red wines. Several transcription factors (TFs) have been identified to be involved in ...regulating PA and anthocyanin biosynthesis in grape berries. However, research on TFs with different regulatory mechanisms for these two biosynthesis branches in grapes remains limited. In this study, we identified an R2R3-MYB TF, VviMYB86, whose spatiotemporal gene expression pattern in grape berries coincided well with PA accumulation but contrasted with anthocyanin synthesis. Both
and
experiments verified that VviMYB86 positively regulated PA biosynthesis, primarily by upregulating the expression of the two leucoanthocyanidin reductase (LAR) genes in the Arabidopsis protoplast system, as well as in
-overexpressing grape callus cultured under 24 h of darkness. Moreover, VviMYB86 was observed to repress the anthocyanin biosynthesis branch in grapes by downregulating the transcript levels of
and
. Overall, VviMYB86 is indicated to have a broad effect on flavonoid synthesis in grape berries. The results of this study will help elucidate the regulatory mechanism governing the expression of the two LAR genes in grape berries and provide new insights into the regulation of PA and anthocyanin biosynthesis in grape berries.
Proanthocyanidins (PAs) are natural polymers of flavan-3-ols, commonly (+)-catechin and (-)-epicatechin. However, exactly how PA oligomerization proceeds is poorly understood. Here we show, both ...biochemically and genetically, that ascorbate (AsA) is an alternative "starter unit" to flavan-3-ol monomers for leucocyanidin-derived (+)-catechin subunit extension in the Arabidopsis thaliana anthocyanidin synthase (ans) mutant. These (catechin)
:ascorbate conjugates (AsA-C
) also accumulate throughout the phase of active PA biosynthesis in wild-type grape flowers, berry skins and seeds. In the presence of (-)-epicatechin, AsA-C
can further provide monomeric or oligomeric PA extension units for non-enzymatic polymerization in vitro, and their role in vivo is inferred from analysis of relative metabolite levels in both Arabidopsis and grape. Our findings advance the knowledge of (+)-catechin-type PA extension and indicate that PA oligomerization does not necessarily proceed by sequential addition of a single extension unit. AsA-C
defines a new type of PA intermediate which we term "sub-PAs".
► Four Chinese pummelo cultivars and one grapefruit cultivar were collected. ► The flavonoid composition in flavedos and juices of samples were analysed. ► Twenty-eight flavonoids were identified.
...The flavonoid composition of flavedos and juices from four Chinese pummelo cultivars (Citrus grandis ‘Shatianyu’, C. grandis ‘Guanximiyu’, C. grandis ‘Yuhuanyu’, and C. grandis ‘Cuixiangtianyu’) and one grapefruit cultivar (Citrus paradisi ‘Changshanhuyu’), was investigated using high-performance liquid chromatography diode array detection electrospray ionisation mass spectrometry (HPLC-DAD-ESI MS/MS). Twenty-eight flavonoids were identified. Naringin was the predominant flavanone in these pummelo varieties, whereas naringin and neohesperidin were the principal flavanones found in C. paradisi ‘Changshanhuyu’. The four pummelo cultivars had higher levels of flavones when compared with the grapefruit. Based on the flavonoid profiles in flavedos and juices, four pummelo cultivars and one grapefruit cultivar were well separated.
Proanthocyanidins (PAs) and anthocyanins are flavonoids that contribute to the quality and health benefits of grapes and wine. Salinity affects their biosynthesis, but the underlying mechanism is ...still unclear. We studied the effects of NaCl stress on PA and anthocyanin biosynthesis in grape suspension cells derived from berry skins of
L. Cabernet Sauvignon using metabolite profiling and transcriptome analysis. We treated the cells with low (75 mM NaCl) and high (150 mM NaCl) salinity for 4 and 7 days. High salinity inhibited cell growth and enhanced PA and anthocyanin accumulation more than low salinity. The salinity-induced PAs and anthocyanins lacked C5'-hydroxylation modification, suggesting the biological significance of delphinidin- and epigallocatechin-derivatives in coping with stress. The genes up-regulated by salinity stress indicated that the anthocyanin pathway was more sensitive to salt concentration than the PA pathway, and WGCNA analysis revealed the coordination between flavonoid biosynthesis and cell wall metabolism under salinity stress. We identified transcription factors potentially involved in regulating NaCl dose- and time-dependent PA and anthocyanin accumulation, showing the dynamic remodeling of flavonoid regulation network under different salinity levels and durations. Our study provides new insights into regulator candidates for tailoring flavonoid composition and molecular indicators of salt stress in grape cells.
Condensed tannins (CT) in wine are derived from the seeds and skins of grapes, and their composition and content contribute to the bitterness/astringency characteristics and ageing potential of the ...wine. Global warming has accelerated the ripening process of grape berries, making them out of sync with seed ripening. To understand the influence of berry ripening on the seed CT composition and content, we analyzed the changes in the soluble and insoluble CT in the seeds of 'Cabernet Sauvignon' grapes from two vineyards over two years. The results showed that the seed-soluble CT presented a slight downward trend in fluctuation during grape berry development, while the insoluble CT increased continuously before the véraison and remained at a high level afterwards. Relatively speaking, a lower sugar increment in developing grape berries favored the conversion of seed CT towards a higher degree of polymerization. The terminal unit of soluble CT was dominated by epigallocatechin gallate, the content of which decreased as the seeds matured. It is suggested that the seeds should be fully matured to reduce this bitter component in tannins. This study provides a reference for us to control the grape ripening process and produce high-quality grapes for wine making.
Phenolic compounds in the non-aged “Cabernet Sauvignon” wines from five wine-growing regions in China were investigated using HPLC-MS. The wines from the regions that have similar “terroir” ...characteristics showed a shorter clustering distance, indicating that similar phenol profiling was present between wines from the Helan mountain of Ningxia and Qilian of Gansu, the drier areas in Northwest China, and between wines from Changli of Hebei and Yantai of Shandong, the wetter areas in Eastern China. Phenol profiling in wines from Deqin of Yunnan (YNDQ), a plateau valley zone in Southwest China, was significantly different with other regions. The YNDQ wines contained extremely high contents of cyanidin derivatives and quercetin derivatives, but had extremely low content of epicatechin. It is suggested that “terroir” characteristics affected the carbon flow to specific branch pathways in the flavonoid metabolism of grape berries, eventually leading to differences in the phenol profiling in the regional wines.
Proanthocyanidins (PAs) derived from grape berries determine the astringency and bitterness of red wines. The two leucoanthocyanidin reductases (VviLAR1 and VviLAR2) are crucial for PA accumulation ...in grapevine. Our previous studies show that the promoter of
contains multiple proposed bHLH transcription factor binding sites, but the corresponding bHLH family regulators remain unknown. Here we identified and functionally characterized VvibHLH93 as a new bHLH transcription factor in PA pathway. Yeast one-hybrid and electrophoretic mobility shift assays showed that VvibHLH93 bound the E/G-box in
promoter. And
gene was mainly expressed in grape flowers, tendrils, stems and berries at PA active stages. Overexpression of
suppressed PA accumulation in grape callus, which was linked to the repression of the transcript levels of two
s. The gene expression analysis in transgenic grape callus and the dual-luciferase assay in tobacco leaves together revealed that VvibHLH93 targeted a broad set of structural genes and transcription factors in flavonoid pathway. This research enriches the regulatory mechanism of the two
genes, and provides new insights into regulating PA content in grape berries.
Liquid chromatography/ultraviolet (LC/UV) and mass spectrometry/mass spectrometry (MS/MS) libraries containing 39 phenolic compounds were established by coupling a LC and an ion trap MS with an ...electrospray ionization (ESI) source, operated in negative ion mode. As a result, the deprotonated M-H- molecule was observed for all the analyzed compounds. Using MS/MS hydroxybenzoic acid and hydroxycinnamic acids showed a loss of CO2 and production of a M-H-44- fragment and as expected, the UV spectra of these two compounds were affected by their chemical structures. For flavonol and flavonol glycosides, the spectra of their glycosides and aglycones produced deprotonated M-H- and A-H- species, respectively, and their UV spectra each presented two major absorption peaks. The UV spectra and MS/MS data of flavan-3-ols and stilbenes were also investigated. Using the optimized LC/MS/MS analytical conditions, the phenolic extracts from six representative wine samples were analyzed and 31 phenolic compounds were detected, 26 of which were identified by searching the LC/UV and MS/MS libraries. Finally, the presence of phenolic compounds was confirmed in different wine samples using the LC/UV and LC/MS/MS libraries.
Volatile components of nine litchi cultivars (10 samples) with high commercial value from Southern China were investigated by means of gas chromatography−mass spectrometry combined with headspace ...solid phase microextraction. A total of 96 volatiles were detected, of which 43 were identified. Seventeen common volatiles in all the samples included linalool, cis-rose oxide, α-terpineol, β-citronellol, geraniol, p-cymene, ethanol, 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, 1-hexanol, (E)-2-hexen-1-ol, 2-ethyl-1-hexanol, 1-octen-3-ol, 1-octanol, ethyl acetate, p,α-dimethylstyrene and 3-tert-butyl-4-hydroxyanisole. Although the volatile composition and concentration varied between these cultivars, the components with the highest OAVs in most cultivars were still cis-rose oxide, trans-rose oxide, 1-octen-3-ol, and geraniol. Two Huaizhi samples from two producing areas exhibited similar volatile profiles, and significantly different from other cultivars according to cluster analysis performed on amounts of major volatile components.
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