Plant phenolics have been for many years a theme of major scientific and applied interest. Grape berry phenolics contribute to organoleptic properties, color and protection against environmental ...challenges. Climate change has already caused significant warming in most grape-growing areas of the world, and the climatic conditions determine, to a large degree, the grape varieties that can be cultivated as well as wine quality. In particular, heat, drought and light/UV intensity severely affect phenolic metabolism and, thus, grape composition and development. In the variety Chardonnay, water stress increases the content of flavonols and decreases the expression of genes involved in biosynthesis of stilbene precursors. Also, polyphenolic profile is greatly dependent on genotype and environmental interactions. This review deals with the diversity and biosynthesis of phenolic compounds in the grape berry, from a general overview to a more detailed level, where the influence of environmental challenges on key phenolic metabolism pathways is approached. The full understanding of how and when specific phenolic compounds accumulate in the berry, and how the varietal grape berry metabolism responds to the environment is of utmost importance to adjust agricultural practices and thus, modify wine profile.
Water availability is arguably the most important environmental factor limiting crop growth and productivity. Erratic precipitation patterns and increased temperatures resulting from climate change ...will likely make drought events more frequent in many regions, increasing the demand on freshwater resources and creating major challenges for agriculture. Addressing these challenges through increased irrigation is not always a sustainable solution so there is a growing need to identify and/or breed drought-tolerant crop varieties in order to maintain sustainability in the context of climate change. Grapevine (Vitis vinifera), a major fruit crop of economic importance, has emerged as a model perennial fruit crop for the study of drought tolerance. This review synthesizes the most recent results on grapevine drought responses, the impact of water deficit on fruit yield and composition, and the identification of drought-tolerant varieties. Given the existing gaps in our knowledge of the mechanisms underlying grapevine drought responses, we aim to answer the following question: how can we move towards a more integrative definition of grapevine drought tolerance?
The contributions of the cuticle and stem scar to blueberry water loss were evaluated in four cultivars. Among the cultivars, 55–69% of the water loss occurred through the cuticle, indicating the key ...role of the cuticle and cuticular waxes in restricting water loss. Cuticular wax content at harvest ranged from 38.12 to 67.00 μg cm−2 across the four cultivars and increased during four-week postharvest storage by an average of 49.5%. Oleanolic and ursolic acid were the most abundant wax compounds. The amount and proportion of oleanolic acid were negatively related to water loss. Wax esters were at low levels in all cultivars, but their content and proportion were directly related to water loss. The stem scar size was directly related to water loss, but only within a given cultivar and not across cultivars. This study provided new knowledge on the role of the cuticular waxes and stem scar in determining water loss in blueberries.
•The cuticle contributes more than the stem scar to blueberry water loss.•Cuticular wax content increases during postharvest cold storage in blueberries.•Oleanolic acid or ursolic acid are the most abundant wax compounds in blueberries.•The wax profile affects blueberry water loss.•Stem scar size affects water loss within a given cultivar but not among cultivars.
Lignin, the second most abundant biopolymer, is a promising renewable energy source and chemical feedstock. A key element of lignin biosynthesis is unknown: how do lignin precursors (monolignols) get ...from inside the cell out to the cell wall where they are polymerized? Modeling indicates that monolignols can passively diffuse through lipid bilayers, but this has not been tested experimentally. We demonstrate significant monolignol diffusion occurs when laccases, which consume monolignols, are present on one side of the membrane. We hypothesize that lignin polymerization could deplete monomers in the wall, creating a concentration gradient driving monolignol diffusion. We developed a two-photon microscopy approach to visualize lignifying Arabidopsis thaliana root cells. Laccase mutants with reduced ability to form lignin polymer in the wall accumulated monolignols inside cells. In contrast, active transport inhibitors did not decrease lignin in the wall and scant intracellular phenolics were observed. Synthetic liposomes were engineered to encapsulate laccases, and monolignols crossed these pure lipid bilayers to form polymer within. A sink-driven diffusion mechanism explains why it has been difficult to identify genes encoding monolignol transporters and why the export of varied phenylpropanoids occurs without specificity. It also highlights an important role for cell wall oxidative enzymes in monolignol export.
•SPME-GC/MS method was validated for determining 73 volatiles in blueberries.•Sensitivity, reproducibility, linearity, and accuracy of the method were evaluated.•Duke, Draper, Bluecrop, Calypso, ...Elliott, and Last Call volatiles were quantified.•Linalool and 2-(E)-hexenal concentrations distinguished the six blueberry cultivars.•(+)-Linalool and (−)-limonene predominate for the six blueberry cultivars.
Blueberry aroma is one of the most important quality traits that influences consumer purchasing decisions. This study aimed to optimize and validate a solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) method for the quantification of 73 volatile compounds in northern highbush blueberries. A SPME extraction of blueberries with water and specific proportions of sodium chloride, citric acid, and ascorbic acid, for 60 min at 50 °C using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was optimal. The method was validated for sensitivity, reproducibility, linearity, and accuracy, and used to quantify volatile compounds through matrix-matched calibration curves in six blueberry cultivars (‘Duke’, ‘Draper’, ‘Bluecrop’, ‘Calypso’, ‘Elliott’, and ‘Last Call’). Terpenes represented the most abundant volatile fraction, followed by aldehydes and alcohols. Linalool and 2-(E)-hexenal were key compounds that differentiated blueberry cultivars via Principal Component Analysis (PCA). Enantiomeric analyses revealed an excess of (−)-limonene, (−)-α-pinene, and (+)-linalool for all cultivars with potential impacts on the blueberry aroma.
Flavonoids impart color and mouthfeel to grapes and wine and are very sensitive to environmental conditions. Growth chamber experiments were performed to investigate the effect of temperature regimes ...and the differences between day/night temperatures on anthocyanins and flavonols in Merlot grapes. Among the regimes tested, the ones with diurnal 20°C determined the highest levels of anthocyanins and flavonols. Higher diurnal temperatures decreased those levels but increased the proportion of methoxylated and acylated species. When regimes with the same day temperature but different night temperatures were compared, differences between day/night temperatures did not affect anthocyanins, unless a difference of 25°C between day and night temperatures was imposed. When regimes with the same night temperature but different day temperatures were compared, the regime with higher day temperature had a lower anthocyanin level. No relationships were observed between the effects of temperature regimes on anthocyanin level and the expression of key anthocyanin genes. However, the effects on anthocyanin acylation level were consistent with the effects on the acyltransferase expression, and the effects on flavonol level were consistent with the effects on the expression of key flavonol genes. This study indicates that, in Merlot grapes, anthocyanins and flavonols are mostly sensitive to day temperatures.
Abstract
Drought events are a major challenge for many horticultural crops, including grapes, which are often cultivated in dry and warm climates. It is not understood how the cuticle contributes to ...the grape berry response to water deficit (WD); furthermore, the cuticular waxes and the related biosynthetic pathways are poorly characterized in this fruit. In this study, we identified candidate wax-related genes from the grapevine genome by phylogenetic and transcriptomic analyses. Developmental and stress response expression patterns of these candidates were characterized across pre-existing RNA sequencing data sets and confirmed a high responsiveness of the pathway to environmental stresses. We then characterized the developmental and WD-induced changes in berry cuticular wax composition, and quantified differences in berry transpiration. Cuticular aliphatic wax content was modulated during development and an increase was observed under WD, with wax esters being strongly up-regulated. These compositional changes were related to up-regulated candidate genes of the aliphatic wax biosynthetic pathway, including CER10, CER2, CER3, CER1, CER4, and WSD1. The effect of WD on berry transpiration was not significant. This study indicates that changes in cuticular wax amount and composition are part of the metabolic response of the grape berry to WD, but these changes do not reduce berry transpiration.
Water deficit caused an increase in grape berry aliphatic cuticular wax load and changes in wax composition, yet these modifications did not reduce the berry cuticle transpiration rate.
Fruit coloration of red-skinned grapevines is mainly due to anthocyanin pigments. We analysed a panel of nine cultivars that included extreme phenotypes for berry colour, ranging from green (absence ...of anthocyanins) to red, purple, violet and blue. Expression of six genes of the anthocyanin pathway coding for flavanone-hydroxylase (F3H), flavonoid 3'-hydroxylase (F3'H), flavonoid 3',5'-hydroxylase (F3'5'H), UDP-glucose:flavonoid-3-O-glucosyltransferase (UFGT), glutathione-S-transferase (GST), O-methyltransferase (OMT) and four transcription factors (MybA, MybB, MybC, MybD) was analysed by quantitative RT-PCR at four developmental stages from before the onset of ripening until full maturity and compared to anthocyanin metabolites.
Total anthocyanin content at full maturity correlated well with the cumulative expression of F3H, UFGT and GST throughout ripening. Transcripts of the last two genes were absent in the green-skinned cultivar 'Sauvignonasse', also known as 'Tocai friulano', and were at least 10-fold less abundant in pale red cultivars, such as 'Pinot gris' and 'Gewürztraminer', compared to fully coloured cultivars. Predominance of tri-hydroxylated anthocyanins (delphinidin, petunidin and malvidin) in cultivars bearing dark berries with violet and blue hue was associated with higher ratios of F3'5'H/F3'H transcription, compared to red-skinned cultivars. Higher levels of OMT transcripts were observed in berries of cultivars that accumulated methoxylated forms of anthocyanins more abundantly than non-methoxylated forms.
Colour variation of the grape berry conforms to a peculiar pattern of genotype-specific expression of the whole set of anthocyanin genes in a direct transcript-metabolite-phenotype relationship. Cumulative mRNA levels of the structural genes and their relative abundance throughout ripening explained per se the final phenotype for anthocyanin content, anthocyanin composition, colour intensity and colour hue of grapes at berry maturity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Anthocyanin biosynthesis is strongly up-regulated in ripening fruit of grapevines (Vitis vinifera L.) grown under drought conditions. We investigated the effects of long-term water deficit on the ...expression of genes coding for flavonoid and anthocyanin biosynthetic enzymes and related transcription factors, genes sensitive to endogenous sugars, abscisic acid (ABA) and environmental (light) stimuli connected to drought stress, and genes developmentally regulated in ripening berries. Total anthocyanin content has increased at harvest in water-stressed (WS) fruits by 37-57% in two consecutive years. At least 84% of the total variation in anthocyanin content was explained by the linear relationship between the integral of mRNA accumulation of the specific anthocyanin biosynthetic gene UDP-glucose : flavonoid 3-O-glucosyltransferase (UFGT) and metabolite content during time series from véraison through ripening. Chalcone synthase (CHS2, CHS3) and flavanone 3-hydroxylase (F3H) genes of the flavonoid pathway showed high correlation as well. Genes coding for flavonoid 3',5'-hydroxylase (F3'5'H) and O-methyltransferase (OMT) were also up-regulated in berries from dehydrated plants in which anthocyanin composition enriched in more hydroxylated and more methoxylated derivatives such as malvidin and peonidin, the grape anthocyanins to which human gastric bilitranslocase displays the highest affinity. The induction in WS plants of structural and regulatory genes of the flavonoid pathway and of genes that trigger brassinosteroid hormonal onset of maturation suggested that the interrelationships between developmental and environmental signalling pathways were magnified by water deficit which actively promoted fruit maturation and, in this context, anthocyanin biosynthesis.
Soft-ripened cheeses (SRCs) are at a higher risk for the growth of the foodborne pathogen Listeria monocytogenes due to favorable moisture content and pH compared to other cheeses.
growth is not ...consistent across SRCs, however, and may be affected by physicochemical and/or microbiome characteristics of the cheeses. Therefore, the purpose of this study was to investigate how the physicochemical and microbiome profiles of SRCs may affect
growth. Forty-three SRCs produced from raw (
= 12) or pasteurized (
= 31) milk were inoculated with
(10
CFU/g), and the pathogen growth was monitored over 12 days at 8°C. In parallel, the pH, water activity (a
), microbial plate counts, and organic acid content of cheeses were measured, and the taxonomic profiles of the cheese microbiomes were measured using 16S rRNA gene targeted amplicon sequencing and shotgun metagenomic sequencing.
growth differed significantly between cheeses (analysis of variance ANOVA;
< 0.001), with increases ranging from 0 to 5.4 log CFU (mean of 2.5 ± 1.2 log CFU), and was negatively correlated with a
. Raw milk cheeses showed significantly lower
growth than pasteurized-milk cheeses (
test;
= 0.008), possibly due to an increase in microbial competition.
growth in cheeses was positively correlated with the relative abundance of Streptococcus thermophilus (Spearman correlation;
< 0.0001) and negatively correlated with the relative abundances of Brevibacterium aurantiacum (Spearman correlation;
= 0.0002) and two
spp. (Spearman correlation;
< 0.01). These results suggest that the cheese microbiome may influence the food safety in SRCs.
Previous studies have identified differences in L. monocytogenes growth between SRCs, but no clear mechanism has yet been elucidated. To the best of our knowledge, this is the first study to collect a wide range of SRCs from retail sources and attempt to identify key factors associated with pathogen growth. A key finding in this research was the positive correlation between the relative abundance of S. thermophilus and the growth of L. monocytogenes. The inclusion of S. thermophilus as a starter culture is more common in industrialized SRC production, suggesting that industrial production of SRC may increase the risk of L. monocytogenes growth. Overall, the results of this study further our understanding of the impact of a
and the cheese microbiome on the growth of L. monocytogenes in SRCs, hopefully leading toward the development of SRC starter/ripening cultures that can prevent L. monocytogenes growth.
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