Alessandra Ferrandino

Drought-induced changes in development and function of grapevine (Vitis spp.) organs and in their hydraulic and non-hydraulic interactions at the whole-plant level: a physiological and molecular update

This review deals with grapevine responses to water stress by examining perturbations to physiological and molecular processes at the root, shoot, leaf and berry levels. Long-distance signalling among organs is also considered. Isohydric or anisohydric Vitis genotypes are described in relation to their response to drought, which is linked to stomatal behaviour. Stomatal regulation of grapevine under abscisic acid and hydraulic control (the latter being linked to embolism formation and recovery in water pathways upstream the stomata) is reviewed and linked to impairments of photosynthetic assimilation. We define three stages of photosynthesis regulation in grapevines that are subjected to progressive water stress on the basis of the main causes of assimilation decline. Early and late contributions of aquaporins, which play a fundamental role in water stress control, are discussed. Metabolic mechanisms of dehydration tolerance are rewieved, and variation linked to differences in transcript abundance of genes involved in osmoregulation, photosynthesis, photorespiration, detoxification of free radicals and coping with photoinhibition. Results of these defence strategies accumulated in berries are reviewed, together with perturbations of their molecular pathways. Features observed in different organs show that grapevine fits well as a complex model plant for molecular and physiological studies on plant drought avoidance/tolerance.

A novel cation-dependent O-methyltransferase involved in anthocyanin methylation in grapevine

Anthocyanins are major pigments in colored grape (Vitis vinifera) berries, and most of them are monomethoxylated or dimethoxylated. We report here the functional characterization of an anthocyanin O-methyltransferase (AOMT) from grapevine. The expression pattern in two cultivars with different anthocyanin methylation profiles (Syrah and Nebbiolo) showed a peak at start ripening (véraison), when the concentrations of all methylated anthocyanins begin to increase. The purified recombinant AOMT protein was active on both anthocyanins and flavonols in vitro, with Km in the micromolar range, and was dependent on divalent cations for activity. AOMT showed a preference for 3′,5′ methylation when a 3′,4′,5′ hydroxylated anthocyanin substrate was tested. In order to assess its in planta activity, we performed transient expression of AOMT in tobacco (Nicotiana benthamiana) leaves expressing the Production of Anthocyanin Pigment1 (PAP1) transcription factor from Arabidopsis (Arabidopsis thaliana). PAP1 expression in leaves induced the accumulation of the nonmethylated anthocyanin delphinidin 3-rutinoside. The coexpression of PAP1 and AOMT resulted in an accumulation of malvidin 3-rutinoside. We also showed that AOMT localized exclusively in the cytoplasm of tobacco leaf cells. These results demonstrate the ability of this enzyme to methylate anthocyanins both in vitro and in vivo, indicating that AOMT plays a major role in anthocyanin biosynthesis in grape berries.

CAROTENOID CLEAVAGE DIOXYGENASE 7 modulates plant growth, reproduction, senescence, and determinate nodulation in the model legume Lotus japonicus

Strigolactones (SLs) are newly identified hormones that regulate multiple aspects of plant development, infection by parasitic weeds, and mutualistic symbiosis in the roots. In this study, the role of SLs was studied for the first time in the model plant Lotus japonicus using transgenic lines silenced for CAROTENOID CLEAVAGE DIOXYGENASE 7 (LjCCD7), the orthologue of Arabidopsis More Axillary Growth 3. Transgenic LjCCD7-silenced plants displayed reduced height due to shorter internodes, and more branched shoots and roots than the controls, and an increase in total plant biomass, while their root:shoot ratio remained unchanged. Moreover, these lines had longer primary roots, delayed senescence, and reduced flower/pod numbers from the third round of flower and pod setting onwards. Only a mild reduction in determinate nodule numbers and hardly any impact on the colonization by arbuscular mycorrhizal fungi were observed. The results show that the impairment of CCD7 activity in L. japonicus leads to a phenotype linked to SL functions, but with specific features possibly due to the peculiar developmental pattern of this plant species. It is believed that the data also link determinate nodulation, plant reproduction, and senescence to CCD7 function for the first time.

Influence of Wine-Grape Skin Hardness on the Kinetics of Anthocyanin Extraction

The main aim of this work was to study in a model, hydroalcoholic solution containing 12% of ethanol and with a pH of 3.20, the kinetics of anthocyanin extraction from Vitis vinifera L. cv. Nebbiolo berries of different skin hardness. This mechanical property was evaluated as the breaking skin force measured by Texture Analysis, a rapid and low-cost analytical technique. Using a TAxT2i Texture Analyzer, a puncture test was carried out on two groups of berries separated according to their density by flotation in order to obtain more homogenous samples and minimize the effect of different stages of ripening of the berries. Among the berries containing 242 ± 8 g/L of reducing sugars in the pulp juice, two groups of berries with different skin hardness were selected: soft (0.26 ± 0.04 N) and hard (0.47 ± 0.05 N). In our experimental conditions, at the end of maceration, the extracts from the higher skin hardness group showed the higher contents of total anthocyanin: +25 mg/L (+9.4%). The anthocyanin profile of extracts, obtained at different extraction times, showed no significant differences among the distribution of different anthocyanins. Only in the early phases of dissolution, did the extracts reveal a dissimilar anthocyanin profile and in the extracts of hard skins higher percentages of cyanidin and peonidin derivatives were present. Additionally, the evolution of skin mechanical properties from veraison to overripe and the influences of biotype on these parameters at harvest are reported in this work.

Profiling of Hydroxycinnamoyl Tartrates and Acylated Anthocyanins in the Skin of 34 Vitis vinifera Genotypes

The diversity of berry skin flavonoids in grape genotypes has been previously widely investigated with regard to major compounds (nonacylated anthocyanins and flavonols), but much less with regard to acylated anthocyanins and hydroxycinnamoyl tartrates (HCTs). In this study, the composition of the phenolic fraction of the berry skin (free and acylated anthocyanins, flavonols, and HCTs) was assessed on 34 grapevine genotypes grown in a collection vineyard in northwestern Italy. The phenolic fraction was profiled on berries collected in the same vineyard, at the same ripening level across two successive vintages. The anthocyanin, HCT, and flavonol profiles were specific of each genotype, and the first two were relatively little affected by the vintage. A wide diversity in the polyphenolic fraction was shown among cultivars. Besides expected discriminatory effects of free anthocyanins and flavonol profiles, principal component analyses allowed a good discrimination of cultivars on the basis of coumaroylated anthocyanins and of the HCT profile. Anthocyanins were mostly acylated by aromatic acids, and acylation was independent from the anthocyanin substrate. HCTs were present mostly as coumaroyl and caffeoyl derivatives, and no correlation was observed between the same acylation patterns of tartrate and of anthocyanins. The results of this study are discussed in the light of new hypotheses on still unknown biosynthetic steps of phenolic substances and of the potential use of these substances in discrimination and identification of different grape cultivars in wines.

Soil water-holding capacity mediates hydraulic and hormonal signals of near-isohydric and near-anisohydric Vitis cultivars in potted grapevines

Grapevine (Vitis vinifera L.) expresses different responses to water stress, depending not only on genotype, but also on the influence of vineyard growing conditions or seasonality. Our aim was to analyse the effects on drought response of two grapevine cultivars growing on two soils, one water draining (WD) containing sand 80% volume and the other water retaining (WR), with no sand. Under these two different water-holding capacities Syrah, displaying a near-anisohydric response to water stress, and Cabernet Sauvignon (on the contrary, near-isohydric) were submitted to water stress in a pot trial. Xylem embolism contributed to plant adaptation to soil water deprivation: in both cultivars during late phases of water stress, however, in Syrah, already at moderate early stress levels. By contrast, Syrah showed a less effective stomatal control of drought than Cabernet Sauvignon. The abscisic acid (ABA) influenced tightly the stomatal conductance of Cabernet Sauvignon on both pot soils. In the near-anisohydric variety Syrah an ABA-related stomatal closure was induced in WR soil to maintain high levels of water potential, showing that a soil-related hormonal root-to-shoot signal causing stomatal closure superimposes on the putatively variety-induced anisohydric response to water stress.

Grapevine adaptations to water stress: new perspectives about soil/plant interactions

Grapevine adaptations to water-stress are described, by focusing on soil/root interactions and root-to-shoot signaling to control both plant water relations and fruit ripening process. Root response to drought, tolerance of available rootstock germoplasm, mechanisms of embolism formation and repair in root, aquaporin control of plant water relations, and abscisic acid biosynthesis and delivery are highlighted, by reviewing recent insights coming from either (eco)physiological literature or viticultural assays addressing vineyard-soil relationships.

Phenolic Substances, Flavor Compounds, and Textural Properties of Three Native Romanian Wine Grape Varieties

In this work, the chemical compositions and texture characteristics of three native Romanian wine grape varieties (Fetească regală, Fetească alba, and Fetească neagră) were studied. We assessed the distinct characteristics directly linked to their phenolic compositions, volatile profiles, and mechanical properties and compared these characteristics with those of Pinot noir grapes. The effect of the growing zone was also evaluated. Various spectrophotometric indices directly related to the phenolic compositions of berry skins and seeds were determined. The detailed phenolic compositions (anthocyanins, hydroxycinnamoyl tartaric acids, and stilbenes) of the skins were determined using high-performance liquid chromatography methods. Free and bound volatile compounds in the berries were quantified by gas chromatography/mass spectrometry. The textural properties of the skins and seeds were measured by instrumental texture analysis. The results showed high diversity among the varieties and zones that affected the enological potential. Among the white varieties, Fetească albă grapes could be less susceptible to browning as a consequence of their lower trans-caffeoyltartaric acid concentration, whereas Fetească regală grapes from Cluj had the highest concentrations of total free and bound volatile compounds, particularly terpenes and norisoprenoids. Among the red varieties, Fetească neagră was identified as a promising variety to be exploited in the future for its particular phenolic characteristics, particularly those grapes grown in Mica. Nevertheless, Fetească neagră grapes grown in Cluj had the highest total glycosidically bound terpene concentrations. Finally, differences in the mechanical and/or acoustic properties of the skins and seeds could strongly influence the kinetics and completeness of phenolic compound extractions.

Screening and evolution of volatile compounds during ripening of ‘Nebbiolo,’ ‘Dolcetto’ and ‘Barbera’ (Vitis vinifera L.) neutral grapes by SBSE–GC/MS

Abstract The evolution of pre-fermentative volatiles and of the global aroma potential in three Italian neutral varieties (‘Nebbiolo,’ ‘Barbera’ and ‘Dolcetto’) was assessed from véraison to harvest by SBSE–GC/MS. C6 and C9 compounds, benzene derivatives, bound monoterpenes and sesquiterpenes showed differences among varieties in quantity and profiles during berry ripening. Quantitatively, the most of total monoterpenes, C-13 norisoprenoids and sesquiterpenes were detected after acid hydrolysis. Among pre-fermentative norisoprenoids, exclusively β-ionone was detected with different kinetics among varieties. Monoterpene accumulation started around véraison with the exception of (E)-geranylacetone, whose content was already high at véraison. (E)-Geranylacetone, deriving from the degradation of carotenoids, could become a target molecule to study indirectly the accumulation of carotenoids. Data allowed to measure the global aroma potential and the pre-fermentative volatiles of grapes: result interpretation suggested a number of implications on biosynthetic processes that have been addressed.

Improved fluorescence-based evaluation of flavonoid in red and white winegrape cultivars

Background and Aims Modern viticulture requires robust, fast, non-destructive methods to assess berry composition. We tested a chlorophyll fluorescence screening method to estimate berry phenolic substances. Methods and Results We focused on anthocyanin and flavonol in red and white cultivars. The ANTH_RG index was dependent on the cultivar anthocyanin profile. In Nebbiolo, in which dihydroxylated anthocyanins prevail, ANTH_RG was 2.4 times higher than in Barbera, in which trihydroxylated anthocyanins prevail. Considering the profiles of the two cultivars at similar anthocyanin concentration and their relative in vitro absorbance, a bathochromic shift of 10 nm emerged, which can explain the different screening effect exerted by anthocyanin on chlorophyll fluorescence. As to flavanols, we propose the calibration of a new spectroscopic index, the FLAV_UV, in coloured and white berries, finding good correlation with flavonol concentration determined analytically (R2 higher than 0.7). Conclusions Spectroscopic indices can estimate the concentration of anthocyanin and flavonol in grape berries. Significance of the Study A calibration curve for Nebbiolo, which has a distinctive anthocyanin profile, and the calibration of a new index, the FLAV_UV, able to estimate flavonol concentration in both red and white cultivars, are described for the first time. These indices can effectively be applied for non-destructive assessment of grape flavonoid.