Protein analysis of moro blood orange pulp during storage at low temperatures

The potential of different ripeness of blood oranges (Citrus sinensis L. Osbeck) for sale in advance after low-temperature storage: Anthocyanin enhancements, volatile compounds, and taste attributes

To explore the optimal early harvest time similar to the ripe fruit qualities, the effects of storage temperatures on maturity indexes, weight losses, colour parameters, anthocyanin profiles, volatile and taste components of blood oranges at six different maturity levels were investigated. Total anthocyanin contents of cold-treated fruits increased to or exceed that of ripe fruits (0.24 ± 0.12 mg/100 g), and fruits harvested from 260 d and 280 d after anthesis shared similar individual anthocyanin profiles to ripe fruits during storage at 8 °C for 30 d and 20 d (III-30 d and IV-20 d groups), respectively. Moreover, comparative analyses of e-nose and e-tongue demonstrated the distances of volatile components and scores of taste attributes including sourness, saltiness, bitterness, sweetness, and umami in III-30 d and IV-20 d groups were close to that of ripe fruits, indicating that the fruits could be sold about 20 to 30 d ahead of the season.

An up-to-date review: differential biosynthesis mechanisms and enrichment methods for health-promoting anthocyanins of citrus fruits during processing and storage

Anthocyanins, naturally found in citrus, play key roles in improving the qualities of citrus fruits and products. Dietary consumption of fruit-derived anthocyanins is concerned increasingly owing to health-promoting properties. However, anthocyanins are vulnerable to many physical and chemical factors during processing and storage, affecting fruit qualities and consumer acceptance. Thus, the aim of this review is to focus on main advances in chemical structures, differential biosynthesis mechanisms, enrichment methods, and bioactivities of anthocyanins in pigmented and unpigmented citrus fruits. In this review, anthocyanin species and concentrations display tissue specificity in citrus, and the chemical structures and contents of main anthocyanins are summarized. For differential biosynthesis mechanisms, the reasons why most citrus fruits lose the ability of anthocyanin biosynthesis compared with pigmented fruits, and the molecular differences of biosynthesis mechanisms in pigmented citrus fruits are both discussed in detail. Furthermore, anthocyanins' enrichment methods (low-temperature stimulus, light irradiation, xenobiotics inductions, and ripeness influence) during processing and storage have been summarized, which achieve quality improvement by promoting structural gene expression, reducing anthocyanin-degrading enzyme activities, or altering DNA methylation status. Meantime, the health benefits of extract from pigmented citrus and their waste are mentioned, which provides a new approach for citrus waste recycling. HIGHLIGHTSChemical structures of individual anthocyanins in citrus are reviewed.Differential anthocyanin biosynthesis in citrus depends on mutations of Ruby genes.Anthocyanins are enriched in response to exogenous stimulus during storage.Health benefits of extract in blood oranges and their waste are summarized.

Improvement of Antioxidant Properties in Fruit from Two Blood and Blond Orange Cultivars by Postharvest Storage at Low Temperature

Numerous studies have revealed the remarkable health-promoting activities of citrus fruits, all of them related to the accumulation of bioactive compounds, including vitamins and phytonutrients. Anthocyanins are characteristic flavonoids present in blood orange, which require low-temperature for their production. Storage at low-temperature of blood oranges has been proven to be a feasible postharvest strategy to increase anthocyanins in those countries with warm climates. To our knowledge, no studies comparing the effect of postharvest storage effect on phenylpropanoid accumulation in cultivars with and without anthocyanins production have been published. We have investigated the effect of postharvest cold storage in flavonoid accumulation in juice from Citrus sinensis L. Osbeck in two different oranges: Pera, a blond cultivar, and Moro, a blood one. Our findings indicate a different response to low-temperature of fruit from both cultivars at biochemical and molecular levels. Little changes were observed in Pera before and after storage, while a higher production of phenylpropanoids (3.3-fold higher) and flavonoids (1.4-fold higher), including a rise in anthocyanins from 1.3 ± 0.7 mg/L to 60.0 ± 9.4 mg/L was observed in Moro concurrent with an upregulation of the biosynthetic genes across the biosynthetic pathway. We show that postharvest storage enhances not only anthocyanins but also other flavonoids accumulation in blood oranges (but not in blond ones), further stimulating the interest in blood orange types in antioxidant-rich diets.

Chilling injury mechanism of hardy kiwifruit (Actinidia arguta) was revealed by proteome of label-free techniques

Refrigeration is an important method to extend shelf life of hardy kiwifruit. However, the inappropriate storage temperature can lead to chilling injury in the fruit. We found that firmness, total soluble solids, and total polyphenolic content of the fruit exposed to 0℃ environment were apparently lower, and titratable acidity content, browning rate, weight loss rate, electrolyte leakage, proline content, and malondialdehyde content were higher obviously than 4℃. A total of 244 differentially expressed proteins were found result from differential temperatures, among which 113 were up-regulated and 131 were down-regulated. Subcellular localization results presented that the differentially expressed proteins which were affected by low temperature were located in cytoplasmic, chloroplast, nuclear, mitochondrial, plasma membrane, and extracellular. Kyoto Encyclopedia of Genes and Genomes analysis showed that the differentially expressed proteins were mainly participated in synthesis of citrate cycle, oxidative phosphorylation, fatty acid biosynthesis, and starch and sucrose metabolism. Protein-protein interaction results revealed that central proteins interaction points respectively are 30S ribosomal proteins, 30S ribosomal protein S7, chloroplastic, cell division cycle 5-like protein, 50S ribosomal protein, ribosomal protein, ribosomal protein L6 protein, and SRP54 subunit protein. The quality deviations of all identified peptides were mainly distributed within 10 ppm, and MS2 has an ideal andromeda score, with more than 87.82% peptide scores above 60 points, and the median peptide score of 99.28 points. Therefore, the results of this study provide important information for new gene revelation and gene interaction relationship in hardy kiwifruit of chilling injury. PRACTICAL APPLICATIONS: Inhibition of cold damage in hardy kiwifruit under low temperature is very important work for the development of its storage industry. However, many qualities of fruit will deteriorate after long-term cold storage and those biological activities of the fruits are regulated by proteins. It is, therefore, of great significance to reveal the key proteins caused cold damage in hardy kiwifruit. Moreover, the study results could provide a scientific information for the quality improvement and genetic modification of hardy kiwifruit.

Effects of Anthocyanins on Vascular Health

Cardiovascular disorders are leading mortality causes worldwide, often with a latent evolution. Vascular health depends on endothelial function, arterial stiffness, and the presence of atherosclerotic plaques. Preventive medicine deserves special attention, focusing on modifiable cardiovascular risk factors, including diet. A diet rich in fruits and vegetables has well-known health benefits, especially due to its polyphenolic components. Anthocyanins, water-soluble flavonoid species, responsible for the red-blue color in plants and commonly found in berries, exert favorable effects on the endothelial function, oxidative stress, inhibit COX-1, and COX-2 enzymes, exert antiatherogenic, antihypertensive, antiglycation, antithrombotic, and anti-inflammatory activity, ameliorate dyslipidemia and arterial stiffness. The present review aims to give a current overview of the mechanisms involved in the vascular protective effect of anthocyanins from the human diet, considering epidemiological data, in vitro and in vivo preclinical research, clinical observational, retrospective, intervention and randomized studies, dietary and biomarker studies, and discussing preventive benefits of anthocyanins and future research directions.

Fungal Infection Induces Anthocyanin Biosynthesis and Changes in DNA Methylation Configuration of Blood Orange [Citrus sinensis L. (Osbeck)]

The biosynthesis of sweet orange anthocyanins is triggered by several environmental factors such as low temperature. Much less is known about the effect of biotic stress on anthocyanin production in sweet orange, although in other species anthocyanins are often indicated as “defense molecules”. In this work, citrus fruits were inoculated with Penicillium digitatum, the causal agent of green mold, and the amount of anthocyanins and the expression of genes related to their biosynthesis was monitored by RT-real time PCR after 3 and 5 days from inoculation (DPI). Moreover, the status of cytosine methylation of DFR and RUBY promoter regions was investigated by McrBC digestion followed in real-time. Our results highlight that fungal infection induces anthocyanin production by activating the expression of several genes in the biosynthetic pathway. The induction of gene expression is accompanied by maintenance of high levels of methylation at the DFR and RUBY promoters in the inoculated fruits, thus suggesting that DNA methylation is not a repressive mark of anthocyanin related gene expression in sweet orange subjected to biotic stress. Finally, by measuring the expression levels of the Citrus DNA demethylase genes, we found that none of them is up-regulated in response to fungal infection, this result being in accordance with the observed maintenance of high-level DFR and Ruby promoter regions methylation.

Rootstock effect on fruit quality, anthocyanins, sugars, hydroxycinnamic acids and flavanones content during the harvest of blood oranges 'Moro' and 'Tarocco Rosso' grown in Spain

The physico-chemical quality parameters (external and internal color, firmness, acidity, total soluble solids, anthocyanins, sugars, hydroxycinnamic acids and flavanones) of 'Moro' and 'Tarocco Rosso' blood oranges grafted onto eight different rootstocks at three harvest time were studied. The rootstocks were 'Carrizo', 'C-35', 'Cleopatra' mandarin, 'Citrus volkameriana', 'Citrus macrophylla', 'Swingle' citrumelo, 'Forner-Alcaide 5' and 'Forner-Alcaide 13'. All studied parameters were highly rootstock/scion-dependent and showed changes throughout harvest. The content of the main anthocyanins revealed their relation with internal fruit color in both cultivars. The rootstocks that led to fruit with the lowest anthocyanins displayed the least sucrose content. The differences detected in the amount of hydroxycinnamic acids (chlorogenic, ferulic and sinapic) and flavanones (hesperidin, narirutin and didymin) related to anthocyanins content, explained phenylpropanoid pathway.

Effect of temperature treatment on fruit quality and immunoregulation of Satsuma (Citrus unshiu Marc.) during storage

Satsuma (Citrus unshiu Marc.) is rich in high levels of nutrients and popular for its unique flavor, but the consumption of satsuma is limited by some adverse reactions in human body. Previous studies have mainly focused on the effects of storage temperature on the postharvest quality of satsumas, and little attention has paid to the effect of postharvest satsumas on human body immunoregulation. The purpose of this study was to explore the differences in fruit quality, and the effect of satsuma fruits stored at different temperatures on human health. Satsumas stored at low temperature (5.8°C, LT) and room temperature (23 ± 2°C, RT) for 60 days were sampled every 10 days to measure the fruit quality. Sixty volunteers were recruited for the oral stimulation experiment of satsumas, and then the effect of satsumas on human health was examined through the immunoregulation of RAW 264.7 macrophages. The results showed that compared with RT treatment, LT treatment could delay the degradation of satsuma fruit quality. Both the results of the volunteer experiment and cell experiment indicated that postharvest temperature treatments could reduce the adverse effects of satsuma fruits on human body. These findings indicated that 10-day storage at room temperature plus subsequent storage at low temperature was the optimal treatment to maintain fruit quality and functional components of postharvest satsumas. This study provides useful information on satsuma consumption and research work from the perspective of immunoregulation evaluation.

Anthocyanin Biosynthesis and DNA Methylation Dynamics in Sweet Orange Fruit [Citrus sinensis L. (Osbeck)] under Cold Stress

The blood red color of pigmented orange fruit varieties [Citrus sinensis L. (Osbeck)] is due to the presence of anthocyanin pigments that largely contribute to determine the high organoleptic qualities and the nutritional properties of the fruits. The content of pigments in sweet orange depends primarily on genetic factors and on environmental conditions. In particular, it has been extensively shown that cold temperature induces an increase of anthocyanin content that is achieved by the induction of the related gene expression. The purpose of our work is to understand the mechanism underlying the color variegation occurring inside the blood oranges during the cold induction of anthocyanin biosynthesis, despite the fact that the entire fruit is genotypically programmed to produce pigments. Therefore, the amount of anthocyanin and the expression of both structural and regulatory genes have been monitored in either high-pigmented (HP) or not/low pigmented (NP) segments of the same fruit during the storage at 4 °C for a total experimental period of 25 days. Our results clearly indicate that the anthocyanin content is directly correlated with the levels of gene transcription, with higher pigmented areas showing higher enhancement of gene expression. Furthermore, we analyzed the reshaping of the DNA methylation status at the promoter regions of genes related to anthocyanin biosynthetic pathway, such as DFR and Ruby. Our results unequivocally demonstrate that in the promoter regions of both DFR and Ruby, the amount of cytosine methylation strongly decreases along the cold storage in the HP areas, whereas it increases in the NP areas of the same fruit, probably causing a partial block of the gene transcription. Finally, by measuring the changes in the expression levels of the Citrus DNA demethylases, we found that DML1 might play a crucial role in determining the observed demethylation of DFR and Ruby promoters, with its expression induced by cold in the HP areas of the fruits. This is the first report in which different levels of gene expression implicated in anthocyanin production in blood orange fruit is correlated with an epigenetic control mechanism such as promoter methylation.

iTRAQ-based quantitative proteomics analysis of cantaloupe (Cucumis melo var. saccharinus) after cold storage

Background

Cantaloupe is susceptible to cold stress when it is stored at low temperatures, resulting in the loss of edible and commercial quality. To ascertain the molecular mechanisms of low temperatures resistance in cantaloupe, a cold-sensitive cultivar, Golden Empress-308 (GE) and a cold-tolerant cultivar, Jia Shi-310 (JS), were selected in parallel for iTRAQ quantitative proteomic analysis.

Results

The two kinds of commercial cultivars were exposed to a temperature of 0.5 °C for 0, 12 and 24 days. We found that the cold-sensitive cultivar (GE) suffered more severe damage as the length of the cold treatment increased. Proteomic analysis of both cultivars indicated that the number of differentially expressed proteins (DEPs) changed remarkably during the chilly treatment. JS expressed cold-responsive proteins more rapidly and mobilized more groups of proteins than GE. Furthermore, metabolic analysis revealed that more amino acids were up-regulated in JS during the early phases of low temperatures stress. The DEPs we found were mainly related to carbohydrate and energy metabolism, structural proteins, reactive oxygen species scavenging, amino acids metabolism and signal transduction. The consequences of phenotype assays, metabolic analysis and q-PCR validation confirm the findings of the iTRAQ analysis.

Conclusion

We found that the prompt response and mobilization of proteins in JS allowed it to maintain a higher level of cold tolerance than GE, and that the slower cold responses in GE may be a vital reason for the severe chilling injury commonly found in this cultivar. The candidate proteins we identified will form the basis of future studies and may improve our understanding of the mechanisms of cold tolerance in cantaloupe.