EjWRKY6 Is Involved in the ABA-Induced Carotenoid Biosynthesis in Loquat Fruit during Ripening.

The yellow-fleshed loquat is abundant in carotenoids, which determine the fruit's color, provide vitamin A, and offer anti-inflammatory and anti-cancer health benefits. In this research, the impact of abscisic acid (ABA), a plant hormone, on carotenoid metabolism and flesh pigmentation in ripening loquat fruits was determined. Results revealed that ABA treatment enhanced the overall content of carotenoids in loquat fruit, including major components like ß-cryptoxanthin, lutein, and ß-carotene, linked to the upregulation of most genes in the carotenoid biosynthesis pathway. Furthermore, a transcription factor, EjWRKY6, whose expression was induced by ABA, was identified and was thought to play a role in ABA-induced carotenoid acceleration. Transient overexpression of EjWRKY6 in Nicotiana benthamiana and stable genetic transformation in Nicotiana tabacum with EjWRKY6 indicated that both carotenoid production and genes related to carotenoid biosynthesis could be upregulated in transgenic plants. A dual-luciferase assay proposed a probable transcriptional control between EjWRKY6 and promoters of genes associated with carotenoid production. To sum up, pre-harvest ABA application could lead to carotenoid biosynthesis in loquat fruit through the EjWRKY6-induced carotenoid biosynthesis pathway.

Melatonin extends shelf life in postharvest okra via delaying fruit softening and reducing weight loss.

BACKGROUND: Melatonin, a hormone present in animals and some plants, has garnered attention for its potential in preserving harvested produce. Softening due to changes in cell wall composition and wilting caused by weight loss are the major reasons for the loss of commercial value in postharvest okra. This study aimed to evaluate the impact of melatonin on the softening and weight loss of postharvest okra. RESULTS: The results revealed that the application of melatonin had a significant influence on the maintenance of fruit firmness by inhibiting the breakdown and dissolution of cell wall polysaccharides by suppressing the expression of specific genes responsible for cell wall degradation in okra. Conversely, melatonin treatment positively influenced the expression of genes involved in the synthesis of cell wall components. Furthermore, the treatment exhibited notable benefits in reducing weight loss in okra, which was accomplished by promoting the closure of stomata - the tiny pores on the surface of the fruit. CONCLUSION: Melatonin could serve as a novel approach to reduce water loss, delay fruit softening and extend the shelf life of okra. © 2024 Society of Chemical Industry.

Catalytic infrared radiation dry-peeling Technology for non-Frozen and Frozen Grapes: Effects on temperature, peeling performance, and quality attributes.

This study introduces catalytic infrared radiation (CIR) heating technology as an eco-friendly alternative to conventional grape lye peeling (LP). The effects of heating time and distance on non-frozen and frozen grapes were assessed for temperature, peeling performance, and quality attributes. The findings indicate that CIR heating achieves complete dry-peeling of grapes. Extended heating times and reduced distances improve peeling performance, with more favorable results observed in frozen grapes compared to non-frozen ones. Grapes peeled using CIR demonstrated enhanced hardness, color, sugar-acid ratio, bioactive compounds, and antioxidant capacity, compared to those peeled using LP. Importantly, the frozen samples preserved their quality after CIR dry-peeling treatment. Based on peeling performance and quality attributes, the optimum heating times are established at 160 s for non-frozen grapes and 50 s for frozen grapes, at a heating distance of 5 cm. Therefore, CIR dry-peeling is recommended as an eco-friendly and quality-enhancing sustainable grape processing technology.

Melatonin delayed senescence by modulating the contents of plant signalling molecules in postharvest okras.

Okra has been widely cultivated worldwide. Consumers appreciate its nutritional value and delicious taste. However, okra is very perishable after harvest because of rapid senescence and high susceptibility to mechanical injuries, which limits its storage life and reduces consumer acceptance. This study examined the influence of melatonin treatment on senescence process and endogenous plant signalling molecules in postharvest okras. The results indicated that melatonin treatment delayed senescence by increasing the endogenous melatonin content through upregulation of its biosynthetic genes. In addition, the treatment increased the contents of indole-3-acetic acid (IAA) and gibberellin (GA) due to the positive modulation of their metabolic and signalling genes. Furthermore, treated okras exhibited higher levels of γ-aminobutyric acid (GABA) but lower abscisic acid (ABA) content, contributing to the delayed senescence process compared to control. Overall, the findings suggested that melatonin postponed senescence in okras fruit by positively regulating endogenous signalling molecules such as melatonin, IAA, GABA, GA, and ABA.

Ultrasound synergistic slightly acidic electrolyzed water treatment of grapes: Impacts on microbial loads, wettability, and postharvest storage quality.

Microbial contamination is the principal factor in the deterioration of postharvest storage quality in grapes. To mitigate this issue, we explored a synergistic treatment which combines ultrasound (US) and slightly acidic electrolyzed water (SAEW), and rigorously compared with conventional water cleaning (CW), exclusive US treatment, and standalone SAEW treatment. The US + SAEW treatment proved to be markedly superior in reducing total bacterial, mold & yeast counts on grapes. Specifically, it achieved reductions of 2.23 log CFU/g and 2.76 log CFU/g, respectively, exceeding the efficiencies of SAEW (0.78, 0.75), US (0.58, 0.65), and CW (0.24, 0.46). The efficacy of this synergistic treatment is attributed to the ultrasound removal of the wax layer on grape skins, which transitions the skin from hydrophobic to hydrophilic. This alteration increases the contact area between the grape surface and SAEW, thereby enhancing the antimicrobial efficacy of SAEW. From a physicochemical quality standpoint, the US + SAEW treatment exhibited multiple advantages. It not only minimized weight loss, color deviations, polyphenol oxidase activity and malondialdehyde synthesis in comparison to CW-treated samples but also preserved firmness, sugar-acid ratio and the activities of key enzymes including phenylalanine ammonia-lyase, superoxide dismutase and catalase, and thus maintaining high levels of total phenolics, total ascorbic acid, total anthocyanins, and antioxidants. Consequently, US + SAEW treatment put off the times of decay onset in grapes by 12 days, outperforming both SAEW (8) and US (4) in comparison to CW. These results highlight the potential of US + SAEW as an effective strategy for maintaining grape quality during their postharvest storage period.

Abscisic acid biosynthesis, metabolism and signaling in ripening fruit.

Fruits are highly recommended nowadays in human diets because they are rich in vitamins, minerals, fibers and other necessary nutrients. The final stage of fruit production, known as ripening, plays a crucial role in determining the fruit's quality and commercial value. This is a complex physiological process, which involves many phytohormones and regulatory factors. Among the phytohormones involved in fruit ripening, abscisic acid (ABA) holds significant importance. ABA levels generally increase during the ripening process in most fruits, and applying ABA externally can enhance fruit flavor, hasten softening, and promote color development through complex signal regulation. Therefore, gaining a deeper understanding of ABA's mechanisms in fruit ripening is valuable for regulating various fruit characteristics, making them more suitable for consumption or storage. This, in turn, can generate greater economic benefits and reduce postharvest losses. This article provides an overview of the relationship between ABA and fruit ripening. It summarizes the effects of ABA on ripening related traits, covering the biochemical aspects and the underlying molecular mechanisms. Additionally, the article discusses the interactions of ABA with other phytohormones during fruit ripening, especially ethylene, and provides perspectives for future exploration in this field.

Ultrasonic synergistic slightly acidic electrolyzed water processing to improve postharvest storage quality of Chinese bayberry.

In the postharvest storage of Chinese bayberry, microbial loads and exogenous contaminants pose significant challenges, leading to rapid decay and deterioration in quality. This study introduced a synergistic approach, combining ultrasonics and slightly acidic electrolyzed water (US + SAEW), to enhance the postharvest storage quality of Chinese bayberry. This approach was benchmarked against conventional water washing (CW), standalone ultrasonic (US), and slightly acidic electrolyzed water (SAEW) processing. Notably, compared to CW, the US + SAEW method enhanced iprodione and procymidone removal rates by 69.62 % and 72.45 % respectively, improved dirt removal efficiency by 122.87 %, repelled drosophila melanogaster larvae by 58.33 %, and curtailed total bacterial, mold & yeast growth by 78.18 % and 83.09 %. Furthermore, it postponed the appearance of sample decay by 6 days, compared to 4 days for both US and SAEW alone. From a physicochemical perspective, compared to CW-treated samples, US + SAEW processing mitigated weight loss and color deviations, retained hardness, amplified the sugar-acid ratio, augmented activities of phenylalanine ammonia-lyase, superoxide dismutase, and catalase enzymes, suppressed polyphenol oxidase activity and malondialdehyde synthesis, and preserved total phenolic, anthocyanin, and antioxidant levels. These findings underscore the potential of US + SAEW as a strategic tool to preserve the quality of Chinese bayberry during postharvest storage.

Micro-nano oxygenated irrigation improves the yield and quality of greenhouse cucumbers under-film drip irrigation.

To study the influence mechanism of micro-nano oxygenated irrigation (MNOI) on greenhouse fruit cucumber in arid and semi-arid cold regions, the yield and quality of greenhouse fruit cucumber were evaluated and verified based on 2 years of observation data. Taking fruit cucumber in Ningxia solar greenhouse as the research object, three dissolved oxygen (DO) levels of MNOI (DO; 6, 7.5, and 9 mg L-1, O1, O2, and O3, respectively) and non-oxygenated irrigation (CK, 4 mg L-1) were set up as the control treatment. Through comparative design, the influence mechanism of different levels of aerobic irrigation on the yield and quality of greenhouse fruit cucumber was studied. The main indicators of fruit cucumber yield and quality increased with dissolved oxygen in irrigation water from 4 to 9 mg L-1. In spring-summer (autumn-winter), compared with CK, the leaf area index (LAI) and net photosynthetic rate (A) increased by 28.83% (28.77%) and 44.90% (35.00%), respectively, and Vitamin C, soluble protein, soluble sugar, soluble solids and total acid content increased by 100.00% (51.88%), 37.78% (61.11%), 34.17% (54.17%), 37.07% (78.72%) and 26.92% (30.67%) respectively, while nitrate content decreased by 44.88% (51.15%), and dry matter accumulation (DMA), soil respiration rate (SRR), microbial carbon (MC), and microbial nitrogen (MN) increased by 49.81% (127.25%), 55.22% (110.34%), 117.50% (90.91%) and 70.37% (74.42%) respectively, and yield, irrigation water use efficiency (IWUE) and soil oxygen content (SO) increased by 22.47% (28.04%), 22.39% (28.05%) and 33.21% (35.33%) respectively. A model of DO in irrigation water and SO was established and the applicability of the model was verified with an average relative error of 2% (less than 5%). MNOI increased SO and soil enzyme activity, enriched soil microorganisms, improved soil microenvironment, promoted water nutrient uptake and growth of root system, increased chlorophyll, photosynthesis and DMA, which improved fruit cucumber yield and quality, and the better DO concentration in irrigation water is 9 mg L-1. The research results provide theoretical support for regulating soil water, fertilizer and air environment, and at the same time, provide feasible ways to improve the quality and efficiency of crops in arid and semi-arid cold regions.

Involvement of a MYB Transcription Factor in Anthocyanin Biosynthesis during Chinese Bayberry (Morella rubra) Fruit Ripening.

Anthocyanin is a class of water-soluble flavonoids found in Chinese bayberry (Morella rubra) that is not only responsible for the variety of colors visible in nature but also has numerous health-promoting benefits in humans. Through comparative transcriptomics, we isolated and identified a transcription factor (TF) of the R2R3-MYB type, MrMYB9, in order to explore the anthocyanin biosynthesis pathway in red and white Chinese bayberries. MrMYB9 transcript was positively correlated with anthocyanin level and anthocyanin biosynthetic gene expression during Chinese bayberry fruit maturation (R-values in the range 0.54-0.84, p < 0.05). Sequence analysis revealed that MrMYB9 shared a similar R2R3 domain with MYB activators of anthocyanin biosynthesis in other plants. MrMYB9 substantially transactivated promoters of anthocyanin biosynthesis-related EBGs (MrCHI, MrF3'H, and MrANS) and LBGs (MrUFGT) upon co-expression of the AtEGL3 gene. Our findings indicated that MrMYB9 may positively modulate anthocyanin accumulation in Chinese bayberry.

Exogenous gibberellin delays maturation in persimmon fruit through transcriptional activators and repressors.

As the harvest season of most fruit is concentrated, fruit maturation manipulation is essential for the fresh fruit industry to prolong sales time. Gibberellin (GA), an important phytohormone necessary for plant growth and development, has also shown a substantial regulatory effect on fruit maturation; however, its regulatory mechanisms remain inconclusive. In this research, preharvest GA3 treatment effectively delayed fruit maturation in several persimmon (Diospyros kaki) cultivars. Among the proteins encoded by differentially expressed genes, 2 transcriptional activators (NAC TRANSCRIPTION FACTOR DkNAC24 and ETHYLENE RESPONSIVE FACTOR DkERF38) and a repressor (MYB-LIKE TRANSCRIPTION FACTOR DkMYB22) were direct regulators of GERANYLGERANYL DIPHOSPHATE SYNTHASE DkGGPS1, LYSINE HISTIDINE TRANSPORTER DkLHT1, and FRUCTOSE-BISPHOSPHATE ALDOLASE DkFBA1, respectively, resulting in the inhibition of carotenoid synthesis, outward transport of an ethylene precursor, and consumption of fructose and glucose. Thus, the present study not only provides a practical method to prolong the persimmon fruit maturation period in various cultivars but also provides insights into the regulatory mechanisms of GA on multiple aspects of fruit quality formation at the transcriptional regulation level.

Hydrogen-rich water treatment increased several phytohormones and prolonged the shelf life in postharvest okras.

Hydrogen-rich water (HRW) treatment has been reported to delay the softening and senescence of postharvest okras, but its regulatory mechanism remains unclear. In this paper, we investigated the effects of HRW treatment on the metabolism of several phytohormones in postharvest okras, which act as regulatory molecules in fruit ripening and senescence processes. The results showed that HRW treatment delayed okra senescence and maintained fruit quality during storage. The treatment upregulated all of the melatonin biosynthetic genes such as AeTDC, AeSNAT, AeCOMT and AeT5H, contributing to the higher melatonin content in the treated okras. Meanwhile, increased transcripts of anabolic genes but lower expression of catabolic genes involved in indoleacetic acid (IAA) and gibberellin (GA) metabolism were observed in okras when treated with HRW, which was related to the enhanced levels of IAA and GA. However, the treated okras experienced lower abscisic acid (ABA) content as compared to the non-treated fruit due to the down-regulation of its biosynthetic genes and up-regulation of the degradative gene AeCYP707A. Additionally, there was no difference in γ-aminobutyric acid between the non-treated and HRW-treated okras. Collectively, our results indicated that HRW treatment increased levels of melatonin, GA and IAA, but decreased ABA content, which ultimately delayed fruit senescence and prolonged shelf life in postharvest okras.

A New Regulatory Network Controls Chilling Injury in Peach Fruit by γ-Aminobutyric Acid.

The control of chilling injury in peach fruit by a new regulator network, that exogenous γ-aminobutyric acid (GABA) regulates the metabolisms of polyamines (PAs), the GABA shunt, and proline, is still unclear. This study found that GABA induced an increase in the expression of PpADC and PpODC and a decrease in the expression of PpPAO expression, resulting in the accumulation of PAs. There was also an increase in the expression of PpGAD, which improved GABA content, and an increase in the expression of PpP5CS and PpOAT, which improved proline content. The correlation analysis showed that an increase in PpADC/PpP5CS expression was closely associated with the accumulation of putrescine and that the synergistic increase in the expression of PpODC and PpGAD/PpP5CS/PpOAT was closely related to the accumulation of spermine, proline, and GABA induced by GABA. Importantly, arginine and PpADC played a key role in putrescine accumulation, whereas ornithine and PpODC/PpOAT played a crucial role in the synergistic accumulation of spermine, proline, and GABA induced by GABA. This study provides new information on GABA-induced cold tolerance in peach fruit.

γ-Aminobutyric acid treatment induced chilling tolerance in postharvest kiwifruit (Actinidia chinensis cv. Hongyang) via regulating ascorbic acid metabolism.

The effect of γ-Aminobutyric acid (GABA) treatment on ascorbic acid (AsA) metabolism and chilling injury in postharvest kiwifruit was studied. The results revealed that kiwifruit treated with GABA displayed higher chilling tolerance and better quality maintenance as compared to the controls. Higher AsA was observed in GABA-treated fruit which was beneficial to cell membrane protection and damage alleviation against chilling mediated oxidative stress. Gene expression analysis found the increased expression of AsA anabolic and regenerative genes and down-regulation of its catabolic genes together could contribute to the elevation of AsA levels in kiwifruit after GABA treatment. In addition, the transcripts of several candidate transcription factors such as bHLHs and HZ1 involved in AsA biosynthesis were also enhanced by GABA treatment. Collectively, our results indicated that GABA induced chilling tolerance in postharvest kiwifruit due to the higher AsA content by positively regulating ascorbate metabolic genes and candidate transcription factors.

Hydrogen-rich water delays fruit softening and prolongs shelf life of postharvest okras.

The effect of hydrogen-rich water (HRW) treatment on softening, cell wall components and cell wall metabolic genes in okras after harvest was studied. The results showed that HRW treatment could maintain fruit firmness and delay softening, thereby prolonging shelf life in okras during storage. The treated okras displayed significantly lower levels water- and chelate-soluble pectins while higher contents of Na2CO3-soluble pectin, hemicellulose and cellulose. The cell wall biosynthesis was maintained by HRW treatment via up-regulating genes involved in biosynthesis of pectin, hemicellulose and cellulose at the beginning of storage. On the contrary, the treatment could inhibit the cell wall disassembly due to the down-regulation of numerous cell wall degradative genes including AePME, AeGAL and AeCX at the end of storage. Taken together, our results suggested that HRW treatment delayed softening and extended shelf life in postharvest okras through modifying cell wall biosynthesis and disassembly at different times of storage.

Comparative Evaluation of Quality Attributes of the Dried Cherry Blossom Subjected to Different Drying Techniques.

Choosing an appropriate drying method is crucial for producing dried cherry blossoms with desirable quality. This study is designed to assess the effects of seven different drying methods-hot-air drying (HAD), infrared hot-air drying (IHAD), catalytic infrared drying (CID), relative humidity drying (RHD), pulsed vacuum drying (PVD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD)-on drying time and various attributes of cherry blossoms, such as appearance, bioactive compounds, antioxidant activity, α-glucosidase activity, and sensory properties. Our findings revealed that MVD recorded the shortest drying time, followed by PVD, CID, IHAD, RHD, HAD, and VFD. In qualities, VFD-dried petals exhibited superior appearance, bioactive compounds, antioxidant activity, and α-glucosidase inhibitory capability; MVD-dried petals were a close second. Furthermore, the quality of tea infusions prepared from the dried petals was found to be significantly correlated with the quality of the dried petals themselves. Regarding sensory attributes, VFD-dried petals produced tea infusions most similar in flavor and taste to those made with fresh petals and received the highest sensory evaluation scores, followed by MVD, PVD, RHD, CID, IHAD, and HAD. These results could offer a scientific foundation for the mass production of high-quality dried cherry blossoms in the future.

γ-Aminobutyric acid treatment induced chilling tolerance in postharvest peach fruit by upregulating ascorbic acid and glutathione contents at the molecular level.

Peach fruit was treated with 5 mM γ-aminobutyric acid (GABA) to further investigate the mechanism by which GABA induced chilling tolerance. Here, we found that GABA not only inhibited the occurrence of chilling injury in peach fruit during cold storage but also maintained fruit quality. Most of the ascorbic acid (AsA) and glutathione (GSH) biosynthetic genes were up-regulated by GABA treatment, and their levels were increased accordingly, thus reducing chilling damage in treated peaches. Meanwhile, the increased transcript of genes in the AsA-GSH cycle by GABA treatment was also related to the induced tolerance against chilling. GABA treatment also increased the expression levels of several candidate ERF transcription factors involved in AsA and GSH biosynthesis. In conclusion, our study found that GABA reduced chilling injury in peach fruit during cold storage due to the higher AsA and GSH contents by positively regulating their modifying genes and candidate transcription factors.

Membrane lipid metabolism influences chilling injury during cold storage of peach fruit.

Peach fruit is prone to chilling injury (CI) during long-term low temperature (LT) storage, and develops protective mechanisms against LT stress. This study revealed that 4 °C storage induced the occurrence of CI in peach fruit by promoting the expression of membrane lipid metabolism genes and phosphatidic acid (PA) accumulation, and stimulated a protective mechanism for peach fruit against LT by increasing diacylglycerol (DAG), triacylglycerol (TAG) and several phosphatidylcholine (PC) components in the later storage stage. In contrast, 0 °C delayed the occurrence of CI in peach fruit by delaying the degradation of phospholipids, upregulation of fatty acid desaturase (FAD) and the process of fatty acid unsaturation, and maintaining higher levels of PC and PE. Results from this study provide new information on the mechanism of CI in peach fruit, and lay the foundation for the transcriptional regulation mechanism of CI and cold tolerance in peach fruit mediated by membrane lipid metabolism.

NAC-mediated membrane lipid remodeling negatively regulates fruit cold tolerance.

Low temperatures are known to destroy cell membranes' structural integrity by affecting the remodeling of their phospholipids. Fruits stored at low temperature are prone to chilling injury, characterized by discoloration, absence of ripening, surface pitting, growth inhibition, flavor loss, decay, and wilting. Phosphatidic acid, a vital second-messenger lipid in plants, is known to accumulate in response to different kinds of stress stimuli. However, the regulatory mechanism of its production from the degradation of phospholipids remains poorly understood. We identified two cold-responsive NAC (NAM/ATAF1/CUC2) transcription factors from bananas, namely, MaNAC25 and MaNAC28, which negatively regulated cold tolerance in banana fruits by upregulating the expression of phospholipid degradation genes in banana fruits. Furthermore, MaNAC25 and MaNAC28 formed a positive feedback loop to induce phospholipid degradation and produce phosphatidic acid. In contrast, ethylene directly inhibited the degradation of phospholipids in banana and transgenic tomato fruits. In addition, ethylene reduced the activity of MaNAC25 and MaNAC28, thereby inhibiting phospholipid degradation. To conclude, NAC-mediated membrane lipid remodeling negatively regulates the cold tolerance of banana and transgenic tomato fruits.

Simultaneous Detection of Seven Alternaria Toxins in Mixed Fruit Puree by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with a Modified QuEChERS.

The presence of Alternaria toxins (ATs) in fruit purees may cause potential harm to the life and health of consumers. As time passes, ATs have become the key detection objects in this kind of food. Based on this, a novel and rapid method was established in this paper for the simultaneous detection of seven ATS (tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene, tentoxin, altenusin, and altertoxin I) in mixed fruit purees using ultra-high performance liquid chromatography-tandem mass spectrometry. The sample was prepared using the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method to complete the extraction and clean-up steps in one procedure. In this QuEChERS method, sample was extracted with water and acetonitrile (1.5% formic acid), then salted out with NaCl, separated on an ACQUITY UPLC BEH C18 with gradient elution by using acetonitrile and 0.1% formic acid aqueous as eluent, and detected by UPLC-MS/MS under positive (ESI+) and negative (ESI-) electrospray ionization and MRM models. Results showed that the seven ATs exhibited a good linearity in the concentration range of 0.5-200 ng/mL with R2 > 0.9925, and the limits of detection (LODs) of the instrument were in the range of 0.18-0.53 µg/kg. The average recoveries ranged from 79.5% to 106.7%, with the relative standard deviations (RSDs) no more than 9.78% at spiked levels of 5, 10, and 20 µg/kg for seven ATs. The established method was applied to the determination and analysis of the seven ATs in 80 mixed fruit puree samples. The results showed that ATs were detected in 31 of the 80 samples, and the content of ATs ranged from 1.32 µg/kg to 54.89 µg/kg. Moreover, the content of TeA was the highest in the detected samples (23.32-54.89 µg/kg), while the detection rate of Ten (24/31 samples) was higher than the other ATs. Furthermore, the other five ATs had similar and lower levels of contamination. The method established in this paper is accurate, rapid, simple, sensitive, repeatable, and stable, and can be used for the practical determination of seven ATs in fruit puree or other similar samples. Moreover, this method could provide theory foundation for the establishment of limit standard of ATs and provide a reference for the development of similar detection standard methods in the future.