Are the Blueberries We Buy Good Quality? Comparative Study of Berries Purchased from Different Outlets.

Blueberries (Vaccinium corymbosum L.) are becoming increasingly popular for their nutritional and health benefits, and their economic value is therefore increasing. The loss of quality that can occur due to softening and fungal attack is an important consideration when marketing blueberries. Despite the added value of blueberries, no studies have been carried out on how the fruit arrives at the outlets just before purchase by the consumer in terms of firmness, physico-chemical parameters, phenolic compounds, and fungal growth. The aim of this work has been, therefore, to investigate possible differences in quality parameters between blueberries purchased from ten different outlets, regardless of the supplier. The results showed that all the samples were of acceptable quality, although they all had a low maturity index at the point of sale. None of the samples studied showed clear signs of fungal decay at the time of purchase, although we were able to grow and identify some pathogen specimens after cultivation. In terms of total phenolic and anthocyanin content, as well as antioxidant activity, all the samples showed low values, possibly due to their postharvest storage, but they were within the expected range for this fruit. On the other hand, differences in the measured parameters were observed between samples of the same cultivar while no differences were found between conventionally and organically grown blueberries. This suggests that preharvest (such as edaphoclimatic conditions, agricultural practices, and cultivars) and postharvest factors (such as treatments used, storage, and transport temperatures) could influence the berry quality when they reach the consumer.

Short-Term Gaseous Treatments Improve Rachis Browning in Red and White Table Grapes Stored at Low Temperature: Molecular Mechanisms Underlying Its Beneficial Effect.

Short-term gaseous treatments improve rachis quality during table grape postharvest, but little is known about the mechanisms involved. In this work, we observed that the application of a 3-day CO2 treatment at 0 °C improved rachis browning of Superior Seedless and Red Globe bunches, affecting the non-enzymatic antioxidant system by reducing the total phenolic content, the antioxidant activity and the expression of different stilbene synthase genes. Lipid peroxidation levels revealed lower oxidative stress in CO2-treated rachis of both cultivars linked to the activation of the enzymatic antioxidant system. Furthermore, whereas a positive correlation was denoted between rachis browning and the accumulation of key ABA regulatory genes in Red Globe bunches, this effect was restricted to ACS1, a key synthetic ethylene gene, in Superior Seedless clusters. This work also corroborated the important role of ethylene-responsive factors in the beneficial effect of the gaseous treatment, not only in the berries but also in the rachis. Finally, the application of the gaseous treatment avoided the induction of cell wall-degrading enzyme-related genes in both cultivars, which could favor the maintenance of rachis quality. This work provides new insight into specific responses modulated by the gaseous treatment focused on mitigating rachis browning independently of the cultivar.

Transcriptomic analysis of CO2-treated strawberries (Fragaria vesca) with enhanced resistance to softening and oxidative stress at consumption.

One of the greatest threats to wild strawberries (Fragaria vesca Mara des Bois) after harvest is the highly perishability at ambient temperature. Breeders have successfully met the quality demands of consumers, but the prevention of waste after harvest in fleshy fruits is still pending. Most of the waste is due to the accelerated progress of senescence-like process after harvest linked to a rapid loss of water and firmness at ambient temperature. The storage life of strawberries increases at low temperature, but their quality is limited by the loss of cell structure. The application of high CO2 concentrations increased firmness during cold storage. However, the key genes related to resistance to softening and cell wall disassembly following transference from cold storage at 20°C remain unclear. Therefore, we performed RNA-seq analysis, constructing a weighted gene co-expression network analysis (WGCNA) to identify which molecular determinants play a role in cell wall integrity, using strawberries with contrasting storage conditions, CO2-cold stored (CCS), air-cold stored (ACS), non-cold stored (NCS) kept at ambient temperature, and intact fruit at harvest (AH). The hub genes associated with the cell wall structural architecture of firmer CO2-treated strawberries revealed xyloglucans stabilization attributed mainly to a down-regulation of Csl E1, XTH 15, Exp-like B1 and the maintenance of expression levels of nucleotide sugars transferases such as GMP and FUT as well as improved lamella integrity linked to a down-regulation of RG-lyase, PL-like and PME. The preservation of cell wall elasticity together with the up-regulation of LEA, EXPA4, and MATE, required to maintain cell turgor, is the mechanisms controlled by high CO2. In stressed air-cold stored strawberries, in addition to an acute softening, there is a preferential transcript accumulation of genes involved in lignin and raffinose pathways. Non-cold stored strawberries kept at 20°C after harvest are characterized by an enrichment in genes mainly involved in oxidative stress and up-expression of genes involved in jasmonate biosynthesis. The present results on transcriptomic analysis of CO2-treated strawberries with enhanced resistance to softening and oxidative stress at consumption will help to improve breeding strategies of both wild and cultivated strawberries.

Postharvest High-CO2 Treatments on the Quality of Soft Fruit Berries: An Integrated Transcriptomic, Proteomic, and Metabolomic Approach.

Soft fruits are appreciated for their taste qualities and for being a source of health-promoting compounds. However, their postharvest is affected by their high respiratory rates and susceptibility to fungal decay. Our aim here is to provide a perspective on the application of short-term high-CO2 treatments at a low temperature to maintain the postharvest quality of soft fruits. This work also suggests using a multi-omics approach to better understand the role of the cell wall and phenolic compounds in maintaining quality. Finally, the contribution of high-throughput transcriptomic technologies to understand the mechanisms modulated by the short-term gaseous treatments is also highlighted.

The Effect of Ethanol Treatment on the Quality of a New Table Grape Cultivar It 681-30 Stored at Low Temperature and after a 7-Day Shelf-Life Period at 20 °C: A Molecular Approach.

Despite the fact that many studies have examined the effectiveness of different gaseous postharvest treatments applied at low temperature to maintain table grape quality, the use of ethanol vapor has hardly been investigated. Thus, this work has studied the effectiveness of ethanol vapor-generating sachets in the maintenance of It 681-30 table grape quality, a new cultivar, during storage at low temperature and after the shelf-life period at 20 °C. To this end, various quality assessments have been carried out and the effect of the ethanol treatment on the expression of different genes (phenylpropanoids, transcription factors, PRs, and aquaporins) was determined. The results indicated that the application of ethanol vapor reduced the total decay incidence, weight loss, and the rachis browning index in It 681-30 grapes stored at 0 °C and after the shelf-life period at 20 °C, as compared to non-treated samples. Moreover, the modulation of STS7 and the different PR genes analyzed seems to play a part in the molecular mechanisms activated to cope with fungal attacks during the postharvest of It 681-30 grapes, and particularly during the shelf-life period at 20 °C. Furthermore, the expression of aquaporin transcripts was activated in samples showing higher weight loss. Although further work is needed to elucidate the role of ethanol in table grape quality, the results obtained in this work provide new insight into the transcriptional regulation triggered by ethanol treatment.

Functional characterization of VviDHN2 and VviDHN4 dehydrin isoforms from Vitis vinifera (L.): An in silico and in vitro approach.

Dehydrins, a family of hydrophilic and intrinsically disordered proteins, are a subgroup of late embryogenesis abundant proteins that perform different protective roles in plants. Although the transition from a disordered to an ordered state has been associated with dehydrin function or interactions with specific partner molecules, the question of how the primary and secondary dehydrin protein structure is related to specific functions or target molecule preferences remains unresolved. This work addresses the in silico sequencing analysis and in vitro functional characterization of two dehydrin isoforms, VviDHN2 and VviDHN4, from Vitis vinifera. Conformational changes suggest potential interactions with a broad range of molecules and could point to more than one function. The in silico analysis showed differences in conserved segments, specific amino acid binding sequences, heterogeneity of structural properties and predicted sites accessible for various post-translational modifications between the sequence of both dehydrins. Moreover, in vitro functional analysis revealed that although they both showed slight antifungal activity, only VviDHN4 acts as a molecular shield that protects proteins from freezing and dehydration. VviDHN4 also demonstrated high potential as a chaperone and reactive oxygen species scavenger, in addition to presenting antifreeze activity, all of which confirms its multifunctional nature. Our findings highlight the significant role of Y-segments and the differential and specific amino acid composition of less conserved segments that are rich in polar/charged residues between S- and K-segments, coupled with post-translational modifications, in modulating and switching dehydrin biological function.

Table Grapes during Postharvest Storage: A Review of the Mechanisms Implicated in the Beneficial Effects of Treatments Applied for Quality Retention.

Table grape is a fruit with increasing interest due to its attributes and nutritional compounds. During recent years, new cultivars such as those without seeds and with new flavors have reached countries around the world. For this reason, postharvest treatments that retain fruit quality need to be improved. However, little is known to date about the biochemical and molecular mechanisms related with observed quality improvements. This review aims to examine existing literature on the different mechanisms. Special attention will be placed on molecular mechanisms which activate and regulate the different postharvest treatments applied in order to improve table grape quality.

Regulation of flavonoid biosynthesis pathway by a single or dual short-term CO2 treatment in black table grapes stored at low temperature.

The application of one or two short-term treatments with high levels of CO2 during 3 days at 0 °C maintained the quality of Autumn Royal table grapes (Vitis vinifera) during storage at 0 °C. We have analyzed how the application of a 3-day gaseous treatment, for one or two times at 0 °C, influences on common (VviPAL, VviCHS, VviCHI, VviF3'H, VviF3'5'H, VviF3H and VviLDOX) and branch-specific (VviFLS1, VviLAR1, VviLAR2, VviANR and VviUFGT) flavonoid gene expression in the skin of Autumn Royal table grapes. Likewise, the content of flavonols, flavan-3-ols and anthocyanins were identified with Q-TOF equipment and quantified by HPLC-quadrupole together with the total phenolic content and the antioxidant capacity by the ABTS and FRAP methods. Moreover, we have also used a solid-state voltammetry methodology to compare the effect of the application of one or two gaseous treatments in the skin of table grapes stored at 0 °C. Results revealed that the application of one or two gaseous treatments modulated the expression of flavonoid gene expression and the levels of catechin, in the case of one application, or quercetin-3-glucoside and five anthocyanins in fruit treated twice, maintaining their levels after 28 days of storage at 0 °C similar to those recorded in freshly harvested fruit. Satisfactorily, the electrochemical approach was useful to distinguish between treated and non-treated samples not only in the first stage of storage but also after 16 days.

Effect of high CO2 levels and low temperature on stilbene biosynthesis pathway gene expression and stilbenes production in white, red and black table grape cultivars during postharvest storage.

Phenolic compounds, such as phytoalexin resveratrol, can be induced in grapes in response to biotic and abiotic stresses and have been related in many healthy effects. Stilbene synthases (STSs) are the key enzyme responsible for resveratrol biosynthesis. They have been already isolated and characterized from several plant species, however, VviSTS is a multigene family and little is known about their modulation in response to the application of gaseous treatments that maintain table grapes quality during postharvest. In this work, we have analyzed the effect of a 3-day CO2 treatment on the modulation of 4 STSs (VviSTS6, VviSTS7, VviSTS16 and VviSTS46) and on the accumulation of different stilbene compounds (resveratrol, resveratrol-glucoside, trans-piceatannol, z-miyabenol and pallidol) during the postharvest storage at 0 °C of white (Superior Seedless, Dominga), red (Red Globe) and black (Autumn Royal) table grapes. Results indicated that the accumulation of the stilbene compounds by the application of CO2 and low temperature storage were cultivar dependent. In white Dominga fruit, accumulation of stilbene compounds increased in CO2-treated samples what seems to be modulated by VviSTS6, VviSTS7 and VviSTS46. However, in Red Globe the accumulation of compounds was mainly due to the cold storage in air and seems to be also mediated by the induction of the same VviSTSs. By contrast, in Superior Seedless and Autumn Royal table grapes the modulation of VviSTSs genes and the stilbene accumulation was independent of the atmosphere storage. Further studies would be needed to elucidate the possible role of transcription factors involved on VviSTSs modulation.

Effect of high levels of CO2 on the electrochemical behavior and the enzymatic and non-enzymatic antioxidant systems in black and white table grapes stored at 0 °C.

BACKGROUND: In this study, we analyzed the effect of the application of high levels of CO2 (20 kPa CO2 + 20 kPa O2 + 60 kPa N2 ) for 3 days at low temperature on a white table-grape cultivar (Superior Seedless) in comparison with a black one (cv. Autumn Royal) in terms of quality parameters. We also used a solid-state voltammetry methodology to analyze the effect of the 3-day gaseous treatment in berry tissues from both cultivars in the first stage of storage. We determined the role of the non-enzymatic (total phenols, total anthocyanins, and antioxidant activity) and the enzymatic antioxidant (catalase (GCAT), ascorbate peroxidase (VcAPX) gene expression) systems in the behaviors of both cultivars. RESULTS: Our results indicate that the application of a 3-day gaseous treatment was effective in maintaining the quality of black and white table grapes for up to 28 days of storage at 0 °C. The electrochemical methodology applied was useful for differentiating between skin and pulp samples, and between black and white table grape cultivars. Some molecular mechanisms were modulated in the skin of both cultivars to overcome oxidative stress, which was not manifested with the same intensity in grapes treated with CO2 for 3 days. However, some differences were observed in relation to the non-enzymatic system. CONCLUSION: The 3-day gaseous treatment was useful to maintain black and white table grape quality at 0 °C. The voltammetry analysis indicated that CO2 -treated samples from the skin and pulp showed more similarity to freshly harvested ones. © 2019 Society of Chemical Industry.

Deciphering the Role of CBF/DREB Transcription Factors and Dehydrins in Maintaining the Quality of Table Grapes cv. Autumn Royal Treated with High CO2 Levels and Stored at 0°C.

C-repeat/dehydration-responsive element binding factors (CBF/DREB) are transcription factors which play a role in improving plant cold stress resistance and recognize the DRE/CRT element in the promoter of a set of cold regulated genes. Dehydrins (DHNs) are proteins that accumulate in plants in response to cold stress, which present, in some cases, CBF/DREB recognition sequences in their promoters and are activated by members of this transcription factor family. The application of a 3-day gaseous treatment with 20 kPa CO2 at 0°C to table grapes cv. Autumn Royal maintained the quality of the bunches during postharvest storage at 0°C, reducing weight loss and rachis browning. In order to determine the role of CBF/DREB genes in the beneficial effect of the gaseous treatment by regulating DHNs, we have analyzed the gene expression pattern of three VviDREBA1s (VviDREBA1-1, VviDREBA1-6, and VviDREBA1-7) as well as three VviDHNs (VviDHN1a, VviDHN2, and VviDHN4), in both alternative splicing forms. Results showed that the differences in VviDREBA1s expression were tissue and atmosphere composition dependent, although the application of high levels of CO2 caused a greater increase of VviDREBA1-1 in the skin, VviDREBA1-6 in the pulp and VviDREBA1-7 in the skin and pulp. Likewise, the application of high levels of CO2 regulated the retention of introns in the transcripts of the dehydrins studied in the different tissues analyzed. The DHNs promoter analysis showed that VviDHN2 presented the cis-acting DRE and CRT elements, whereas VviDHN1a presented only the DRE motif. Our electrophoretic mobility shift assays (EMSA) showed that VviDREBA1-1 was the only transcription factor that had in vitro binding capacity to the CRT element of the VviDHN2 promoter region, indicating that the transcriptional regulation of VviDHN1a and VviDHN4 would be carried out by activating other independent routes of these transcription factors. Our results suggest that the application of high CO2 levels to maintain table grape quality during storage at 0°C, leads to an activation of CBF/DREBs transcription factors. Among these factors, VviDREBA1-1 seems to participate in the transcriptional activation of VviDHN2 via CRT binding, with the unspliced form of this DHN being activated by high CO2 levels in all the tissues analyzed.

Expression Profiles and DNA-Binding Affinity of Five ERF Genes in Bunches of Vitis vinifera cv. Cardinal Treated with High Levels of CO2 at Low Temperature.

Ethylene response factors (ERFs) play an important role in plants by regulating defense response through interaction with various stress pathways. After harvest, table grapes (Vitis vinifera L.) are subject to a range of problems associated with postharvest storage at 0°C, such as fungal attack, water loss and rachis browning. The application of a 3-day high CO2 treatment maintained fruit quality and activated the induction of transcription factors belonging to different families such as ERF. In this paper, we have isolated five VviERFs from table grapes cv. Cardinal, whose deduced amino acid sequence contained the conserved apetalous (AP2)/ERF domain. The phylogeny and putative conserved motifs in VviERFs were analyzed and compared with those previously reported in Vitis. VviERFs-c gene expression was studied by quantitative real-time RT-PCR in the different tissues of bunches stored at low temperature and treated with high levels of CO2. The results showed that in most of the tissues analyzed, VviERFs-c gene expression was induced by the storage under normal atmosphere although the application of high levels of CO2 caused a greater increase in the VviERFs-c transcript accumulation. The promoter regions of two PRs (pathogenesis related proteins), Vcchit1b and Vcgns1, were obtained and the in silico analysis revealed the presence of a cis-acting ethylene response element (GCC box). In addition, expression of these two PR genes was analyzed in the pulp and rachis of CO2-treated and non-treated table grapes stored at 0°C and results showed significant correlations with VviERF2-c and VviERF6L7-c gene expression in rachis, and between VviERF11-c and Vcchit1b in pulp. Finally by using electro mobility shift assays, we denoted differences in binding of VviERFs to the GCC sequences present in the promoters of both PRs, with VviERF6L7-c being the only member which did not bind to any tested probe. Overall, our results suggest that the beneficial effect of high CO2 treatment maintaining table grape quality seems to be mediated by the regulation of ERFs and in particular VviERF2-c might play an important role by modulating the expression of PR genes.

Low Temperature and Short-Term High-CO2 Treatment in Postharvest Storage of Table Grapes at Two Maturity Stages: Effects on Transcriptome Profiling.

Table grapes (Vitis vinifera cv. Cardinal) are highly perishable and their quality deteriorates during postharvest storage at low temperature mainly because of sensitivity to fungal decay and senescence of rachis. The application of a 3-day CO2 treatment (20 kPa CO2 + 20 kPa O2 + 60 kPa N2) at 0°C reduced total decay and retained fruit quality in early and late-harvested table grapes during postharvest storage. In order to study the transcriptional responsiveness of table grapes to low temperature and high CO2 levels in the first stage of storage and how the maturity stage affect these changes, we have performed a comparative large-scale transcriptional analysis using the custom-made GrapeGen GeneChip®. In the first stage of storage, low temperature led to a significantly intense change in grape skin transcriptome irrespective of fruit maturity, although there were different changes within each stage. In the case of CO2 treated samples, in comparison to fruit at time zero, only slight differences were observed. Functional enrichment analysis revealed that major modifications in the transcriptome profile of early- and late-harvested grapes stored at 0°C are linked to biotic and abiotic stress-responsive terms. However, in both cases there is a specific reprogramming of the transcriptome during the first stage of storage at 0°C in order to withstand the cold stress. Thus, genes involved in gluconeogenesis, photosynthesis, mRNA translation and lipid transport were up-regulated in the case of early-harvested grapes, and genes related to protein folding stability and intracellular membrane trafficking in late-harvested grapes. The beneficial effect of high CO2 treatment maintaining table grape quality seems to be an active process requiring the induction of several transcription factors and kinases in early-harvested grapes, and the activation of processes associated to the maintenance of energy in late-harvested grapes.

Differential regulation of dehydrin expression and trehalose levels in Cardinal table grape skin by low temperature and high CO2.

Dehydrins and trehalose are multifunctional protective biomolecules that play a role in counteracting cellular damage during dehydrative stresses. In this paper, we studied dehydrin isoform patterns, dehydrin gene expression and trehalose levels in the skin of Cardinal (Vitis vinifera L.) table grapes, along with their regulation by different cold postharvest storage conditions. Immunoanalysis with K-segment antibody recognizes four constitutive dehydrins (from 17 to 44 kDa) that are tightly regulated by low temperature and high CO2. Phosphatase treatment showed that DHN44 and DHN22 isoforms are phosphorylated polypeptides, while MALDI-TOF MS and MS/MS analysis suggested that 44 kDa polypeptide may be a dehydrin homodimer. At the transcriptional level, dehydrins are also regulated by low temperature and high CO2, showing a fairly good correlation with their mRNA levels. Trehalose was quantified by high performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), revealing a progressive increase of this metabolite throughout storage at 0 °C and the sudden transitory increases in short-term high CO2-treated fruit. We propose that the constitutive presence and up-regulation of dehydrins and trehalose during low temperature postharvest storage could be positively correlated with the relative chilling tolerance of table grapes and the adaptive responses activated by high CO2 levels to preserve cell water status and to counteract the disruption of physiological processes during cold storage.

Effects of high CO2 levels on fermentation, peroxidation, and cellular water stress in Fragaria vesca stored at low temperature in conditions of unlimited O2.

To better understand the tolerance of strawberries (Fragaria vesca L.) to high CO2 in storage atmospheres, fermentation and cellular damage were investigated. Fruits were stored for 3 and 6 days at 0 °C in the presence of different CO2 levels (0, 20, or 40%) with 20% O2. Changes in pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) gene expression and in fermentative metabolites, as well as in bound water and malondialdehyde (MDA) concentrations, were analyzed. In strawberries stored without added CO2, up-regulation of PDC and ADH was not associated with an increase in fermentative metabolites. By contrast, moderate ethanol fermentation in fruits exposed to 20% CO2 seems to be essential to maintain fruit metabolism, reducing both lipid peroxidation and cellular water stress. However, if the CO2 concentration increases (40%), the excess acetaldehyde and ethanol produced were closely correlated with a decrease in bound water and production of MDA.

The crucial role of Φ- and K-segments in the in vitro functionality of Vitis vinifera dehydrin DHN1a.

Dehydrins (DHNs), group II LEA (Late Embryogenesis Abundant) proteins, are among the most commonly observed proteins which accumulate in plants in response to cold and any other environmental factors, causing the dehydration of cells. In previous studies, we isolated a YSK2-type VvcDHN1a gene from table grapes (Vitis vinifera cv. Cardinal) which presented two spliced variants (the spliced, DHN1a_s and the unspliced, DHN1a_u). Their expression was induced by low temperature storage and CO2, although with different accumulation patterns. DHN1a_u codifies for a truncated YS protein lacking Ф- and K-segments, which might affect its functionality. In this work, we expressed both DHN1a_s and DHN1a_u recombinant proteins in Escherichia coli. We carried out a number of in vitro assays to analyze the implications that Ф- and K-segments have in the protective role of VvcDHN1 against different abiotic stresses and their antifungal activity against the fungal pathogen Botrytis cinerea. Our results showed that unlike DHN1a_u, DHN1a_s has a potent cryoprotective effect on lactate dehydrogenase activity, protects malate dehydrogenase against dehydration and partially inhibits B. cinerea growth. Moreover, the DHN1a promoter presented cis-regulatory elements related to cold and drought, as well as biotic stress-related elements. We also observed that both spliced variants interact weakly with DNA, suggesting that K-segments are not involved in DNA binding. Overall, this work highlights the crucial role of Ф- and K-segments in DHNs function in plant response to abiotic stress showing for the first time, the potential role of the V. vinifera DHN1a_s in the protection against freezing and dehydration as well as inhibiting B. cinerea growth.

Two cold-induced family 19 glycosyl hydrolases from cherimoya (Annona cherimola) fruit: an antifungal chitinase and a cold-adapted chitinase.

Two cold-induced chitinases were isolated and purified from the mesocarp cherimoyas (Annona cherimola Mill.) and they were characterised as acidic endochitinases with a Mr of 24.79 and 47.77kDa (AChi24 and AChi48, respectively), both family 19 glycosyl hydrolases. These purified chitinases differed significantly in their biochemical and biophysical properties. While both enzymes had similar optimal acidic pH values, AChi24 was enzymatically active and stable at alkaline pH values, as well as displaying an optimal temperature of 45°C and moderate thermostability. Kinetic studies revealed a great catalytic efficiency of AChi24 for oligomeric and polymeric substrates. Conversely, AChi48 hydrolysis showed positive co-operativity that was associated to a mixture of different functional oligomeric states through weak transient protein interactions. The rise in the AChi48 kcat at increasing enzyme concentrations provided evidence of its oligomerisation. AChi48 chitinase was active and stable in a broad acidic pH range, and while it was relatively labile as temperatures increased, with an optimal temperature of 35°C, it retained about 50% of its maximal activity from 5 to 50°C. Thermodynamic characterisation reflected the high kcat of AChi48 and the remarkably lower ΔH(‡), ΔS(‡) and ΔG(‡) values at 5°C compared to AChi24, indicating that the hydrolytic activity of AChi48 was less thermodependent. In vitro functional studies revealed that AChi24 had a strong antifungal defence potential against Botrytis cinerea, whereas they displayed no cryoprotective or antifreeze activity. Hence, based on biochemical, thermodynamic and functional data, this study demonstrates that two acidic endochitinases are induced at low temperatures in a subtropical fruit, and that one of them acts in an oligomeric cold-adapted manner.

Characterisation and functionality of fructo-oligosaccharides affecting water status of strawberry fruit (Fragraria vesca cv. Mara de Bois) during postharvest storage.

Water status and analyses of free sugars, sugar-alcohols and fructo-oligosaccharides (FOS) were carried out in Fragaria x vesca treated with different high CO(2) concentrations applied to minimise damage caused by storage at 0°C. The thermodynamic parameters such as the amount of unfrozen water (U(w)), T(g), T(g)('), and peak position of the O-H stretching vibration were determined in various saccharides including FOS (1-kestose, nystose and kestopentaose) by infrared spectroscopy studies and differential scanning calorimetry. Beneficial high CO(2) treatment (20%) avoided the reduction of unfreezable water fraction and increased endogenous FOS levels, in contrast to that observed in air-stored and in those exposed to higher CO(2) levels (40%). The direct FOS-water interaction, possibly within the hydrogen-bond network of cellular structures, could explain the maintenance of water status, cell integrity and the low water leakage levels in 20% CO(2)-treated fruit at values similar to those found in freshly harvested fruit.

Increasing catechin and procyanindin accumulation in high-CO2-treated Fragaria vesca strawberries.

This paper deals with the impact of low temperature and high CO2 levels on flavonols, proanthocyanidins, and anthocyanins, synthesized via branched pathways from common precursors, in strawberries (Fragaria vesca L.). Flavonoids were identified with Q-TOF equipment and quantified by HPLC-quadrupole. Proanthocyanins B1 and B3 accumulated in CO2-treated strawberries, whereas in untreated (air) fruit, flavonoid production was redirected toward anthocyanin accumulation with a sharp decrease in catechin and procyanidin B3 levels. Moreover, in CO2-treated fruit, mainly in those with 20% CO2, anthocyanin accumulation did not decline. Due to its antifungal activity, catechin induction in CO2-treated strawberries could explain the capacity of high CO2 treatments to reduce fungal decay. Ascorbic acid content increased in 40% CO2-treated fruits, whereas in those treated with 20% CO2 an increase in flavonol content was observed. Despite these differences, similar antioxidant capacities were found in untreated and CO2-treated Mara de Bois strawberries.

Unraveling the roles of CBF1, CBF4 and dehydrin 1 genes in the response of table grapes to high CO2 levels and low temperature.

CBFs (C-repeat binding factors) are transcription factors that are rapidly induced by low temperature and that recognize the CRT/DRE element in the promoter of a set of cold regulated genes, the CBF regulon. Dehydrins are proteins that accumulate in plants under stress conditions, such as low temperature, and some form part of the CBF regulon. To investigate their role in the response of table grape clusters to 0°C long storage as well as to 3-day high CO2 postharvest treatment, we isolated two partial CBF genes (VvcCBF1 and VvcCBF4) and a full-length dehydrin (VvcDHN1a) from Vitis vinifera cv. Cardinal. Hydrophobic cluster analysis (HCA) identified differences in the secondary and tertiary structure between Vitis CBF4s and CBF1s. Overall, our results showed that, in table grapes, the expression of CBF genes is induced mainly in response to CO2 treatment, suggesting that the response of DHN1a in this fruit could be attributed to a cold-inducible CBF-independent pathway.