24-Epibrassinolide delays senescence in harvested kiwifruit through effects on mitochondrial membrane and antioxidant activity

The transcription factors AdNAC3 and AdMYB19 regulate kiwifruit ripening through brassinosteroid and ethylene signaling networks

The pivotal role of ethylene (ETH) in fruit ripening has been extensively studied; however, the function of brassinosteroids (BRs) in regulating fruit ripening remains poorly understood. Specifically, the mechanism by which BRs interact with ETH to affect kiwifruit (Actinidia deliciosa) ripening is unclear. Our research showed that 2 genes encoding transcription factors, AdNAC3 and AdMYB19, and the fruit softening gene AdEXP3 (encoding a cell wall expansion protein, expansin 3) were upregulated by ETH and downregulated by BRs. Furthermore, AdNAC3 and AdMYB19 positively regulated the activity of the AdEXP3 promoter, and AdNAC3 positively regulated the promoter activity of AdMYB19. The physical interaction between AdNAC3 and the B-box-type zinc finger protein AdBBX32 affected fruit ripening. Transient overexpression and silencing experiments revealed that ETH upregulated and BRs downregulated the expression of AdNAC3 and AdMYB19, thereby regulating the expression level of AdEXP3 and participating in pectin degradation. Stable transformation of AdNAC3 in tomato fruits accelerated fruit color change and promoted fruit ripening. These results indicate that AdNAC3 and AdMYB19 are involved in the hormone interaction between BRs and ETH in regulating kiwifruit ripening, providing insights into the molecular mechanisms underlying the crosstalk between BRs and ETH.

Improvement of antioxidant capacity, aroma quality, and antifungal ability of cherry by phenyllactic acid treatment during low temperature storage

Introduction

Sweet cherries (Prunus avium L.) are highly valued for their taste and nutrients but are prone to decay due to their delicate skin and high respiration rate. Traditional chemical preservatives have drawbacks like residues and resistance, prompting the search for natural alternatives. Phenylactic acid (PLA) has shown promise due to its antibacterial and antioxidant properties, making it a potential natural preservative to extend cherry shelf life.

Methods

'Stella' sweet cherries were treated with varying concentrations of PLA (0, 2, 4, 8, 16 mmol·L-1) and stored at 4°C. Key quality indicators, including firmness, total acidity, total soluble solids, weight loss, decay index, and antioxidant activity, were assessed over time. Additionally, HPLC, GC-MS, GC-IMS, colony counts, in vivo inhibition analyses were conducted to evaluate phenolic content, aroma compounds and antifungal ability.

Results and Discussion

PLA at 8 mmol·L-1 effectively maintained cherry quality by reducing weight loss and decay of cherries, delaying the decline of firmness, while enhancing antioxidant capacity, flavor stability, and antifungal ability. Higher concentrations (16 mmol·L-1) provided stronger antimicrobial effects but caused slight surface wrinkling. Thus, 8 mmol·L-1 was optimal, balancing preservation and appearance, making it a promising natural preservative for extending cherry shelf life.

Recent Advances in Postharvest Application of Exogenous Phytohormones for Quality Preservation of Fruits and Vegetables

The increasing global population has heightened the demand for food, leading to escalated food production and, consequently, the generation of significant food waste. Factors such as rapid ripening, susceptibility to physiological disorders, and vulnerability to microbial attacks have been implicated as contributing to the accelerated senescence associated with food waste generation. Fruits and vegetables, characterized by their high perishability, account for approximately half of all food waste produced, rendering them a major area of concern. Various postharvest technologies have thus been employed, including the application of phytohormone treatments, to safeguard and extend the storability of highly perishable food products. This review, therefore, explores the physicochemical properties and biological aspects of phytohormones that render them suitable for food preservation. Furthermore, this review examines the effects of externally applied phytohormones on the postharvest physiology and quality attributes of fresh produce. Finally, the review investigates the mechanisms by which exogenous phytohormones preserve food quality and discusses the associated limitations and safety considerations related to the use of these compounds in food applications.

Salicylic Acid Spray Delays Sand Pear Fruit Senescence during Room Temperature Shelf Life by Regulating Antioxidant Capacity and Senescence-Related Genes

'Whangkeumbae' (Pyrus pyrifolia) is a variety of sand pear fruit well-known for its smooth surface and good taste. However, the fruit quality is adversely affected by postharvest ethylene production. Therefore, improving postharvest shelf life by regulating fruit senescence is critical to promoting the 'Whangkeumbae' fruit industry. Here, we investigated the effect of salicylic acid (SA) spray on fruit senescence in sand pears during room temperature shelf life. Exogenous SA reduced polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content during room temperature shelf life. Additionally, SA effectively maintained the fruit skin coloration and increased the activity of antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). SA treatment inhibited PpPPO1 expression and upregulated PpSOD1, PpAPX6, and PpGST2 expression. Furthermore, SA application downregulated the expression of PpACO2, PpEIN3a, PpNCED1, and PpAOC2, while upregulating PpNPR-1, PpTAR2, and PpCOMT1 during room temperature shelf life. SA treatment also influenced cell wall metabolism and modification genes by inhibiting PpPG1, PpPME2, and PpCEL3 and inducing PpPGIP1 expression. Additionally, SA treatment affected sugar and acid metabolism genes and increased the expression of PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH, but suppressed the expression of PpcyNADP-ME. The Pearson correlation analysis indicated that PPO activity and MDA content were positively correlated with the expression of PpPPO1, PpACO2, PpEIN3a, PpNCED1, PpAOC2, PpPG1, PpPME2, PpCEL3, and PpcyNDA-MDH. Conversely, these factors were negatively associated with the activities of SOD, POD, CAT, and APX, as well as the expression levels of PpSOD1, PpPOD1, PpCAT1, PpAPX6, PpGST2, PpNPR-1, PpTAR2, PpCOMT1, PpPGIP1, PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH. Our results reveal that exogenous SA could delay fruit senescence in sand pear fruit by regulating various biochemical and molecular mechanisms and can be used to effectively extend fruit shelf life during room temperature storage. However, further research is necessary to determine whether the fruits sprayed with SA are suitable for direct human consumption.

Efficacy of 24-epibrassinolide-chitosan composite coating on the quality of 'Williams' bananas during ripening

BACKGROUND

Banana fruit undergo rapid metabolic changes following the induction of ripening. They result in excessive softening, chlorophyll degradation, browning, and senescence during postharvest life. As part of a continuous effort to extend fruit shelf life and maintain the best possible quality, this study examined the effect of a 24-epibrassinolide (EBR) and chitosan (CT) composite coating on 'Williams' bananas ripening in ambient conditions. Fruit were soaked in 20 μM EBR, 10 g L-1 CT (w/v), and 20 μM EBR + 10 g L-1 CT solutions for 15 min and were kept at 23 ± 1 °C and 85-90% (RH) for 9 days.

RESULTS

The combined treatment (20 μM EBR + 10 g L-1 CT) clearly delayed fruit ripening; bananas treated with this showed less peel yellowing, weight loss, and total soluble solids, and greater firmness, titratable acidity, membrane stability index, and ascorbic acid content than the untreated control. After the treatment, the fruit also presented higher radical scavenging capacity, and higher total phenol and flavonoid content. The activity of polyphenoloxidase and hydrolytic enzymes was lower, and that of peroxidase was higher in both the peel and pulp of all the treated fruit than in the control.

CONCLUSION

The combined treatment (20 μM EBR + 10 g L-1 CT) is suggested as an effective composite edible coat to retain the quality of 'Williams' bananas during ripening. © 2023 Society of Chemical Industry.

Effect of Chitosan-24-Epibrassinolide Composite Coating on the Quality Attributes of Late-Harvested Pomegranate Fruit under Simulated Commercial Storage Conditions

This study evaluated the efficacy of chitosan (CH) functionalized with 24-epibrassinolide (EBR) coating in terms of preserving the postharvest quality of late-harvested pomegranate (cv. Wonderful) fruit. Late-harvested pomegranate fruit were immersed for 3 min in different surface treatment solutions—CH 1.5% (w/v), CH + 2 µM EBR, CH + 5 µM EBR, CH + 10 µM EBR and CH + 15 µM EBR—and distilled water was used as a control treatment. The fruit were air-dried and subjected to long storage duration at 5 °C with 85 ± 5 RH for 12 weeks. At 4-week sampling intervals, a batch of fruits was placed at 21 ± 2 °C and 65–70% RH for a further 3 d period to simulate retail conditions before measurements were taken. Fruit physiological responses, physico-chemical properties, phytochemical contents, antioxidant capacity and physiological disorders were monitored during storage. The results showed that the CH-EBR composite edible coatings significantly (p < 0.05) delayed degradative processes due to senescence. The CH-EBR treatments delayed colour, texture and total soluble solids (TSS) degradation and reduced weight loss, respiration, electrolyte leakage and spoilage compared to the control and CH treatment. The treatment effect was more noticeable on fruit treated with CH + 10 µM EBR, which exhibited lower weight loss (18.19%), respiration rate (7.72 mL CO₂ kg⁻¹ h⁻¹), electrolyte leakage (27.54%) and decay (12.5%), and maintained higher texture (10.8 N) and TSS (17.67 °Brix) compared to the untreated fruit with respective values of 24.32%, 18.06 mL CO₂ kg⁻¹ h⁻¹, 43.15%, 37.5%, 8.32 N and 17.03 °Brix. This was largely attributed to the significantly higher antioxidant content, including the ascorbic acid content, total phenol content, total anthocyanin content and DPPH (radical scavenging activity), of the coated fruit compared to the control fruit. Therefore, CH + 10 µM EBR treatment is recommended as a postharvest management strategy to improve the quality preservation of late-harvested pomegranate fruit during storage.

Brassinosteroids in Plants: Crosstalk with Small-Molecule Compounds

Brassinosteroids (BRs) are known as the sixth type of plant hormone participating in various physiological and biochemical activities and play an irreplaceable role in plants. Small-molecule compounds (SMCs) such as nitric oxide (NO), ethylene, hydrogen peroxide (H₂O₂), and hydrogen sulfide (H₂S) are involved in plant growth and development as signaling messengers. Recently, the involvement of SMCs in BR-mediated growth and stress responses is gradually being discovered in plants, including seed germination, adventitious rooting, stem elongation, fruit ripening, and stress responses. The crosstalk between BRs and SMCs promotes plant development and alleviates stress damage by modulating the antioxidant system, photosynthetic capacity, and carbohydrate metabolism, as well as osmotic adjustment. In the present review, we try to explain the function of BRs and SMCs and their crosstalk in the growth, development, and stress resistance of plants.

The effect of exogenous 24-epibrassinolide pretreatment on the quality, antioxidant capacity, and postharvest life of wucai (Brassica campestris L.)

The quality of green leafy vegetables is easily lost during the postharvest period. The effect of exogenous 24-epibrassinolide (EBR) pretreatment on the quality of wucai was evaluated in the present study. Wucai plants were sprayed twice with 0.1 μM EBR before harvesting. Two storage temperatures were tested: 25°C and 4°C. At 4°C, EBR pretreatment significantly delayed the degradation of the pigment and plant water loss. Furthermore, we measured the activity of key enzymes of the ascorbic acid (AsA)-glutathione (GSH) cycle, the content of the main metabolites, and the expression of the AsA metabolism-related genes in leaves. The results indicated that all three plants showed stronger antioxidant capacity after EBR pretreatment. At 4°C and 25°C, the storage time of wucai was 20 days and 7 days after EBR treatment, while the samples could be stored for 14 days and 4 days without EBR treatment application, respectively. At 4°C, the nutritional properties of wucai pretreated with EBR, such as total free amino acids, total soluble sugar, and cellulose contents, were higher than those of the control, while the content of nitrite and lignin was lower than that of the control. Hence, EBR pretreatment was able to enhance the antioxidant capacity of wucai, maintain normal leaf color and shape during storage, and delay the decline of nutritional properties; therefore, EBR pretreatment has potential commercial value for prolonging the market life of wucai.

Citral Delays Postharvest Senescence of Kiwifruit by Enhancing Antioxidant Capacity under Cold Storage

Citral is an aliphatic aldehyde extracted from citrus essential oil. The aim of the study was to examine how citral treatment affects the weight loss, firmness, respiration, and ripening index, as well as the antioxidant capacity of kiwifruit (Actinidia chinensis cv. ‘Jinkui’). The citral treatment was seen to reduce the weight loss, softening, and fruit respiration compared to control fruits. Citral treatment also had an inhibitory effect on ripening index, O2•− production rate, and malondialdehyde (MDA) accumulation. The degradations of ascorbic acid (AsA) content, total flavonoids content (TFC), and total phenolics content (TPC) were also suppressed by citral. In contrast, citral treatment induces the activation of antioxidant enzyme system such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Collectively, the results indicated that citral treatment delays postharvest senescence and prolongs storage life by enhancing antioxidant capacity in harvested kiwifruits. These findings suggest that citral has the potential to be used as a promising natural preservative for the extension of postharvest quality in harvested kiwifruit.