Physiological responses of a halophytic shrub to salt stress by Na2SO4 and NaCl: oxidative damage and the role of polyphenols in antioxidant protection

Salt stress conditions lead to increased production of reactive oxygen species (ROS) in plant cells. Halophytes have the ability to reduce these toxic ROS by means of a powerful antioxidant system that includes enzymatic and non-enzymatic components. In this research, we used the halophytic shrub Prosopis strombulifera to investigate whether the ability of this species to grow under increasing salt concentrations and mixtures was related to the synthesis of polyphenolic compounds and to the maintenance of leaf pigment contents for an adequate photosynthetic activity. Seedlings of P. strombulifera were grown hydroponically in Hoagland's solution, gradually adding Na2SO4 and NaCl separately or in mixtures until reaching final osmotic potentials of −1, −1.9 and −2.6 MPa. Control plants were allowed to develop in Hoagland's solution without salt. Oxidative damage in tissues was determined by H2O2 and malondialdehyde content. Leaf pigment analysis was performed by high-performance liquid chromatography with ultraviolet, and total phenols, total flavonoids, total flavan-3-ols, condensed tannins, tartaric acid esters and flavonols were spectrophotometrically assayed. Treatment with Na2SO4 increased H2O2 production and lipid peroxidation in tissues and induced a sharp increase in flavonoid compounds (mainly flavan-3-ols) and consequently in the antioxidant activity. Also, Na2SO4 treatment induced an increased carotenoid/chlorophyll ratio, which may represent a strategy to protect photosystems against photooxidation. NaCl treatment, however, did not affect H2O2 content, lipid peroxidation, pigments or polyphenols synthesis. The significant accumulation of flavonoids in tissues under Na2SO4 treatment and their powerful antioxidant activity indicates a role for these compounds in counteracting the oxidative damage induced by severe salt stress, particularly, ionic stress. We demonstrate that ionic interactions between different salts in salinized soils modify the biochemical and morpho-physiological responses of P. strombulifera plants to salinity.Fil: Reginato, Mariana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquímicas y Naturales. Cátedra de Fisiología Vegetal; ArgentinaFil: Castagna, Antonella. Università degli Studi di Pisa; ItaliaFil: Furlan, Ana Laura. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Castro, Stella Maris. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Ranieri, Annamaria. Università degli Studi di Pisa; ItaliaFil: Luna, Maria Virginia. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquímicas y Naturales. Cátedra de Fisiología Vegetal; Argentin

Short-Term CO2 Treatment of Harvested Grapes (Vitis vinifera L., cv. Trebbiano) before Partial Dehydration Affects Berry Secondary Metabolism and the Aromatic Profile of the Resulting Wine

High CO2 concentrations applied to harvested horticultural products can modify primary and secondary metabolism. This work reports the metabolic responses to short-term CO2 treatments of white-skinned grapes (cv Trebbiano) undergoing postharvest partial dehydration. The influence of CO2 treatments on the aroma profile of the derived sweet wine was also assessed. Harvested grapes were treated with gaseous CO2 (30%) or air (control) for 24 h and then dehydrated (about 45% of weight loss) before vinification. Lipophilic and phenolic compounds of grape skin and the wine aroma profile were analyzed. In CO2-treated berries, the lipophilic and phenolic compounds decreased at a reduced and faster rate, respectively, during dehydration. Aroma profile of wine from CO2-treated grapes showed a slight but significantly higher content of glycosylated C13 and terpene compounds, and a decrease/absence of free acids, vanillin derivates and other phenol volatiles. The higher content of volatile alcohols in wine from treated berries suggests that the alcoholic fermentation was triggered. CO2 application before the withering process of Trebbiano grapes affects the aroma profile of the resulting wine by altering the free:glycosylated volatiles ratio. This study provides information on the possible use of CO2 as metabolic elicitor to modulate the aroma profile of the resulting wines obtained after grape dehydratio

The dominant allele Aft induces a shift from flavonol to anthocyanin production in response to UV-B radiation in tomato fruit

The introgression of the A ft allele into domesticated tomato induced a shift from flavonol to anthocyanin production in response to UV-B radiation, while the hp - 1 allele negatively influenced the response of flavonoid biosynthesis to UV-B. Introgression of the dominant allele Anthocyanin fruit (Aft) from Solanum chilense induces anthocyanin accumulation in the peel of tomato (Solanum lycopersicum L.) fruit. UV-B radiation can influence plant secondary metabolism regulating the expression of several genes, among which those involved in flavonoid biosynthesis. Here, we investigated whether post-harvest UV-B treatment could up-regulate flavonoid production in tomato fruits and whether the Aft allele could affect flavonoid biosynthesis under UV-B radiation. Mature green fruits of an anthocyanin-rich tomato mutant line (SA206) and of its wild-type reference, cv. Roma, were daily subjected to post-harvest UV-B treatment until full ripening. Up-regulation of CHS and CHI transcription by UV-B treatment induced flavonoid accumulation in the peel of cv. Roma. Conversely, UV-B decreased the total flavonoid content and CHS transcript levels in the SA206 peel. SA206 being a double mutant containing also hp-1 allele, we investigated also the behavior of hp-1 fruit. The decreased peel flavonoid accumulation and gene transcription in response to UV-B suggest that hp-1 allele is involved in the marked down-regulation of the flavonoid biosynthesis observed in SA206 fruit. Interestingly, in SA206, UV-B radiation promoted the synthesis of delphinidin, petunidin, and malvidin by increasing F3'5'H and DFR transcription, but it decreased rutin production, suggesting a switch from flavonols to anthocyanins. Finally, although UV-B radiation does not reach the inner fruit tissues, it down-regulated flavonoid biosynthesis in the flesh of both genotypes. This study provides, for the first time, evidence that the presence of the functional Aft allele, under UV-B radiation, redirects flavonoid synthesis towards anthocyanin production and suggests that the hp-1 allele negatively influences the response of flavonoid biosynthesis to UV-B

Carotenoids, Phenolic Profile, Mineral Content and Antioxidant Properties in Flesh and Peel of Prunus persica Fruits during Two Maturation Stages

Carotenoids and phenolic profile, antioxidant activity as well as concentrations of selected macronutrients (K, N, Mg, Ca and Na) and micronutrients (Zn, Cu and Mn) in flesh and peel of peach fruit were recorded at two harvest dates. Predominant mineral was potassium, followed by calcium, magnesium and sodium. The concentration of most micronutrients was greater in the peel than in the flesh especially in early season. The concentration of most elements in flesh and peel decreased during fruit maturation. Total carotenoids content varied with respect to the cultivar. β-cryptoxanthin and β-carotene were the major carotenoids in both tissues and flesh contain the lowest amounts. Neochlorogenic acid, chlorogenic acid, catechin, epicatechin, gallic acid, rutin, quercetin-3-O-galactoside, cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside, were detected in both peel and flesh, with chlorogenic acid and catechin being the predominant components. Peel extracts showed markedly higher antioxidant activities, when estimated by ABTS or DPPH assays, than the flesh counterparts, consistent with the observed higher phenolic content. Overall, total phenolics levels increased at full ripening stage in both peel and flesh. The results found herein provide important data on carotenoids, phenolic and macro- and micronutrient changes during fruit growth, and emphases peach fruit as a potential functional food

Aroma profile of Fuji apples treated with gelatin edible coating during their storage

This study aimed to detect possible changes in the volatile organic compounds (VOCs) of Fuji apples induced by gelatin-based edible coating (EC), during 21 days of storage at room temperature. VOCs were analyzed by solid-phase micro extraction-gas chromatography-mass spectrometry. Data were analyzed by one-way ANOVA and principal component analysis. Control apples showed a greater presence of total aldehydes and acids at 7 and 14 days, respectively, while coated apples were characterized by higher proportions of alcohols (from 1.3- to 2-fold) at 7 day till the end of the storage. The higher ethanol proportions detected in coated apples (154-fold higher after 7 days) indicate a likely partial anaerobiosis, confirmed by the lower CO2 emission (reaching -68% after 21 days). Esters responsible of the varietal aroma of Fuji were identified also in coated fruits, suggesting that gelatin did not modify the typical aroma extensively. Acetate esters, normally increasing with maturity, were less concentrated in coated apples (-78% 2-methylbutyl acetate and -73% hexyl acetate, after 1 and 7 days respectively), suggesting a likely slowdown of the ripening due to the EC. Further investigation is needed to improve this storage technology considering that aroma is an important determinant of food quality

Physiological effects of short acute UVB treatments in Chenopodium quinoa Will

Increased ultraviolet B (UVB) radiation due to global change can affect plant growth and metabolism. Here, we evaluated the capacity of quinoa to resist under short acute UVB irradiation. Quinoa was daily exposed for 30 or 60 min to 1.69 W m−2 UVB. The results showed that 30 min exposure in 9 d-course did not cause severe alterations on photosynthetic pigments and flavonoids, but a significant increase of antioxidant capacity was observed. Otherwise, 60 min UVB in 5 d-course reduced almost all these parameters except for an increase in the de-epoxidation of xanthophyll cycle pigments and led to the death of the plants. Further studies of gas exchange and fluorescence measurements showed that 30 min UVB dramatically decrease stomatal conductance, probably associated to reactive oxygen species (ROS) production. Inhibition of photosynthetic electron transport was also observed, which could be a response to reduce ROS. Otherwise, irreversible damage to the photosynthetic apparatus was found with 60 min UVB probably due to severe ROS overproduction that decompensates the redox balance inducing UVB non-specific signaling. Moreover, 60 min UVB compromised Rubisco carboxylase activity and photosynthetic electron transport. Overall, these data suggest that quinoa modulates different response mechanisms depending on the UVB irradiation dosage

Corrigendum: UV-B Pre-treatment Alters Phenolics Response to Monilinia fructicola Infection in a Structure-Dependent Way in Peach Skin

[This corrects the article DOI: 10.3389/fpls.2018.01598.]

Postharvest UV-B exposure drives changes in primary metabolism, phenolic concentration, and volatilome profile in berries of different grape (Vitis vinifera L.) varieties

BACKGROUND The ultraviolet-B (UV-B) radiation can alter grape metabolism during berry development, but little is known on the effect of postharvest UV-B exposure. In this study, we evaluated the effect of postharvest UV-B exposure on berry primary and secondary metabolites in four grapevine varieties (Aleatico, Moscato bianco, Sangiovese, and Vermentino) in order to evaluate the possibility to increase the grape quality and its nutraceutical properties. RESULTS The treatment did not significantly affect the berry primary metabolism in terms of organic acids, carbohydrates, and amino acids profile, regardless of the variety. UV-B exposure reduced the total anthocyanin content, particularly the tri-substituted and di-substituted forms in Aleatico and Sangiovese, respectively. An overall negative effect of UV-B irradiation on the flavonols profile of Aleatico, Moscato bianco, and Vermentino berries was found, whereas it enhanced the quercetin, myricetin and kaempferol concentration in Sangiovese. The free fraction of berry volatile organic compounds increased in UV-B-treated Aleatico and Moscato bianco berries, especially C-13-norisoprenoids and volatile phenols, as well as key monoterpenes, such as the linalool derivatives. However, higher concentrations of glycosylated monoterpenes and C-13-norisoprenoids were measured in Sangiovese and Vermentino berries treated with UV-B. CONCLUSION This study provides new insights on the effect of postharvest UV-B radiation on berry secondary metabolism, highlighting a different modulation between varieties and suggesting the potential use of this technique to increase some nutraceutical and quality characteristics of grape berry