Effect of benzothiadiazole treatment on improving the mitochondrial energy metabolism involved in induced resistance of apple fruit during postharvest storage

β-Aminobutyric acid activates SA-signalling systemic acquired resistance in peach fruit by suppressing the circadian clock associated protein1

Circadian clock regulates plant development and physiology by anticipating daily environmental changes. Here we studied the core clock protein involved in β-aminobutyric acid (BABA)-inducible systemic acquired resistance (SAR) resistance to Rhizopus stolonifer in peach fruit. BABA elicitation barely primed the accumulation of jasmonate or ethylene, whose regulation was associated with morning-loop gene expression. Notably, BABA-induced resistance depended on the upregulation of salicylic acid (SA) signalling, accompanied by increased transcription of specific evening-loop genes. Through Y2H screening, pull-down and co-IP analyses, CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), a morning-expressed clock protein repressed by BABA, was identified as an interacting partner of NPR1 in regulating SA-dependent SAR. A CUT&Tag analysis indicated that the association of CCA1 with its target genes, which are enriched in EE or CBS motifs, was involved in SA pathway. Furthermore, EMSA, DLR, Y3H and Co-ip assays suggested that CCA1 did not directly affect the expression of SA-inducible genes but instead hindered the interaction between NPR1 and TGA1. Overexpression of PpCCA1 attenuated the transcription of SA-responsive PR genes, while mutation of PpCCA1 elevated these expressions. Collectively, PpCCA1 functions as a negative regulator of NPR1-dependent SA signalling through antagonistic crosstalk with the NPR1-TGA1 system, but BABA activates SAR by suppressing PpCCA1 in peach fruit.

Inducing resistance of postharvest fruits and vegetables through acibenzolar-S-methyl application: A review of implications and mechanisms

Significant losses of vegetables and fruits occur at multiple stages, including harvest, sorting, storage, and transportation, primarily due to mechanical damage, pathogen invasion, and the natural process of senescence. To mitigate postharvest decay and maintain superior quality of produce, conventional techniques such as low temperature storage and synthetic fungicide treatment are widely employed. Acibenzolar-S-methyl (ASM), an effective plant resistance inducers, has demonstrated its efficacy in protecting against a diverse range of fungal and bacterial pathogens. The present review primarily concludes that exogenous application of ASM effectively maintains postharvest quality, delays senescence, and controls decay of postharvest fruits and vegetables through the following mechanisms: (1) modulation of signal transduction pathways including Ca2+ signal, H2O2, and mitogen-activated protein kinase cascades; (2) regulation of reactive oxygen species metabolism; (3) accumulation of pathogenesis-related proteins; (4) activation of the phenylpropanoid pathway; (5) regulation of energy metabolism; and (6) mediation of fatty acid metabolism. Taken together, ASM is a potent activator that enhances resistance against a wide range of postharvest pathogens and effectively preserves the storage quality of horticultural products.

Ursolic Acid Induces Multifaceted Defense Responses Against Postharvest Blue Mold Rot in Apple Fruit

The disease resistance and defense mechanisms induced by ursolic acid (UA) in apple fruit were studied in this paper. UA was directly mixed with potato dextrose agar and broth media to assay its antifungal activity in vitro. The results showed that UA exerted inherent antifungal activity and directly inhibited the in vitro growth and spore germination of Penicillium expansum. Its half-maximal inhibitory concentration for hyphal growth was 175.6 mg L-1. Apple fruit were immersed in UA solution, followed by inoculation with P. expansum, to measure their disease response. The results demonstrated that UA induced significant disease resistance in apple fruit and that its mechanisms are multifaceted and associated with defensive and antioxidative enzymes and the phenylpropanoid pathway. Chitinase, β-1,3-glucanase, peroxidase, and polyphenol oxidase were activated and maintained at relatively high levels. The activities of enzymes and their metabolites in the phenylpropanoid pathway, including phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate coenzyme A ligase were significantly increased; accordingly, total phenolics, flavonoid, and lignin contents were significantly increased. The activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase were enhanced upon UA treatment, while catalase activity was suppressed, which regulates hydrogen peroxide accumulation to defend against pathogens. These results suggest that UA induces defense responses against postharvest blue mold rot in apple fruit and that it may be a promising elicitor to induce fruit disease resistance to control postharvest decay.

Melatonin Maintains Postharvest Quality in Fresh Gastrodia elata Tuber by Regulating Antioxidant Ability and Phenylpropanoid and Energy Metabolism During Storage

Melatonin treatment has been reported to effectively preserve and improve the postharvest quality of fruits and vegetables during storage. This research focused on examining the significance of melatonin on maintaining the quality of fresh Gastrodia elata tubers throughout the storage period. The findings demonstrated that melatonin application effectively reduced the deterioration rate and inhibited the rise in respiratory rate, malondialdehyde content, and weight loss, while slowing down the decline in soluble solid content. Melatonin treatment led to a decrease in hydrogen peroxide production and a rise in non-enzymatic antioxidant concentrations, including ascorbic acid. Furthermore, it boosted both the activity and expression of indispensable antioxidant enzymes, like superoxide dismutase, catalase, and ascorbate peroxidase. Additionally, melatonin treatment promoted the accumulation of total phenols, flavonoids, and lignin in fresh G. elata, while enhancing both the activity and expression of critical enzymes in the phenylpropanoid pathway, including phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate-CoA ligase. Moreover, melatonin treatment boosted the activity and expression of energy-associated enzymes including H+-ATPase, succinate dehydrogenase, Ca2+-ATPase, and cytochrome C oxidase, contributing to the improvement of energy levels in fresh G. elata. In summary, melatonin enhances the antioxidant potential and reduces oxidative damage in fresh G. elata by activating reactive oxygen species, phenylpropanoid metabolism, and energy metabolism, thereby maintaining its postharvest quality.

Dicyclohexylcarbodiimide and disodium succinate induce the change of energy metabolism in relation to longan pulp breakdown

Compared to control longan, DCC-treated longan had higher pulp breakdown index, lower ATP, ADP and EC levels, and lower H+, Ca2+ and Mg2+-ATPase activities. On day 6, DCC-treated longan presented 18% higher pulp breakdown index, with 44%, 9% and 31% lower levels of ATP, ADP and EC, respectively. Additionally, DCC-treated longan showed 29%, 53%, 37% lower activity of H+-ATPase, 34%, 54%, 4% lower activity of Ca2+-ATPase, and 13%, 21%, 6% lower activity of Mg2+-ATPase in the membranes of plasma, vacuole, and mitochondria, respectively. Whereas, DS-treated longan manifested the opposite trends of DCC treatment. These results suggest that the accelerated pulp breakdown in DCC-treated longan was linked to energy deficiency and reduced energy production. However, DS treatment restrained pulp breakdown occurrence in fresh longan by maintaining a higher energy level through the elevated energy production and ATPase activity.

Biochemical and metabolomics analyses reveal the mechanisms underlying ascorbic acid and chitosan coating mediated energy homeostasis in postharvest papaya fruit

Papaya is a climacteric fruit that undergoes rapid ripening and quality deterioration during postharvest storage, resulting in significant economic losses. This study employed biochemical techniques and targeted metabolomics to investigate the impact of exogenous AsA + CTS application on the energy metabolism regulation of papaya fruit during postharvest storage. We found that AsA + CTS treatment significantly increased the levels of key metabolic compounds and enzymes, such as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and the energy charge, as well as the succinic acid content and the activities of succinic dehydrogenase (SDH), cytochrome c oxidase (CCO), H+-ATPase, and Ca2+-ATPase. Moreover, AsA + CTS coating augmented the nicotinamide adenine dinucleotide kinase (NADK) activity and increased the NADH and NADPH concentrations. Regarding sugar metabolism, it increased the activities of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase and raised d-glucose-6-phosphate levels. These findings suggest that AsA + CTS coating application can mitigate the metabolic deterioration and sustain a primary metabolism homeostasis in papaya fruit by enhancing the tricarboxylic acid (TCA) cycle and pentose phosphate pathway (PPP), thereby preserving their quality attributes during postharvest storage.

X-rays irradiation maintains redox homeostasis and regulates energy metabolism of fresh figs (Ficus carica L. Siluhongyu)

In this study, figs were irradiated with X-rays doses of 1.0, 3.0, and 5.0 kGy and stored at 4 °C for 20 d to evaluate effects of X-ray on redox homeostasis and energy metabolism in figs. Non-irradiated figs were recorded as control group. Results indicated that 3.0 kGy X-rays delayed fig color discoloration by inhibiting the ΔE* values. The electrolyte leakage, MDA and O2-· levels of figs were significantly alleviated. Energy metabolism assay revealed that 3.0 kGy X-rays could significantly maintain higher activities of H+-ATPase, Ca2+-ATPase, SDH, CCO, G6PDH and 6PGDH of figs. 3.0 kGy X-rays also retained mitochondria membrane integrity of figs. Furthermore, 3.0 kGy X-rays resulted in 26.09 % higher NADK activity and 16.30 % lower NADH content than the control. The study proves that X-ray irradiation can be used as figs preservation means to maintain redox homeostasis and regulate energy metabolism, thus lengthening the shelf life of figs.

Induced Resistance in Fruit and Vegetables: A Host Physiological Response Limiting Postharvest Disease Development

Harvested fruit and vegetables are perishable, subject to desiccation, show increased respiration during ripening, and are colonized by postharvest fungal pathogens. Induced resistance is a strategy to control diseases by eliciting biochemical processes in fruits and vegetables. This is accomplished by modulating the progress of ripening and senescence, which maintains the produce in a state of heightened resistance to decay-causing fungi. Utilization of induced resistance to protect produce has been improved by scientific tools that better characterize physiological changes in plants. Induced resistance slows the decline of innate immunity after harvest and increases the production of defensive responses that directly inhibit plant pathogens. This increase in defense response in fruits and vegetables contributes to higher amounts of phenols and antioxidant compounds, improving both the quality and appearance of the produce. This review summarizes mechanisms and treatments that induce resistance in harvested fruits and vegetables to suppress fungal colonization. Moreover, it highlights the importance of host maturity and stage of ripening as limiting conditions for the improved expression of induced-resistance processes.

PpMYB1 and PpNPR1 interact to enhance the resistance of peach fruit to Rhizopus stolonifer infection

MYB transcription factors play important role in stress-resistance of plants. Nevertheless, the function of MYB TFs in peach Rhizopus rot remains poorly understood. Herein, Pichia guilliermondii treatment activated resistance against Rhizopus stolonifer, as illustrated by reductions in the incidence rate and severity of Rhizopus rot disease, increased enzyme activities and gene expression of chitinase (CHI) and β-1,3-glucanase (GLU), and enhancement of energy production by inducing the activities and expression of H⁺-ATPase and Ca²⁺-ATPase, succinate dehydrogenase (SDH), and cytochrome c oxidase (CCO). Moreover, an R1-type MYB, PpMYB1, from peach fruit was induced during R. stolonifer infection and in response to P. guilliermondii treatment. PpMYB1 activated the transcription of PpCHI-EP3 and PpGLU-like genes and the energy metabolism-related gene PpH⁺-ATPase1 by directly targeting the MBS element. Importantly, PpMYB1 interacted with PpNPR1 to form a heterodimer, which was conducive to enhancing the activation of target gene transcription. Collectively, our findings suggest that PpMYB1 cooperates with PpNPR1 to positively regulate disease resistance by activating the disease defense system and energy metabolism in peaches.

Benzothiadiazole enhances ascorbate recycling and polyphenols accumulation in blueberry in a cultivar-dependent manner

Benzothiadiazole (BTH) is a functional analogue of salicylic acid able to induce systemic acquired resistance in many horticultural crops. The aim of the work was to investigate how BTH may affect i) fruit quality, ii) ascorbic acid (AsA) oxidation and recycling metabolism and iii) phenolic compounds accumulation, during development and ripening of berries from the two selected cultivars. Blueberry (Vaccinium corymbosum L.) plants (cv 'Brigitta' and 'Duke') were treated with 0.118 mM BTH every two weeks during ripening, then all fruits of each plant were harvested and divided in four developmental stages. Results indicated that BTH had no marked effects on fruit quality parameters. During the first developmental stage, BTH negatively affected dry matter in both cv, while soluble solids and AsA content were affected in 'Duke'. In fully ripe berries, BTH reduced dry matter in 'Duke' and enhanced soluble solids content in 'Brigitta', while diminishing titratable acidity. AsA content was positively affected by BTH in 'Duke', but not in 'Brigitta'. The effect of BTH on the enzymes involved in AsA recycling was recorded in berries at the third (fruit more than half pigmented) and fourth developmental stages. After treatment, in both cv ascorbate peroxidase (APX) activity increased in fully ripe berries, while monodehydroascorbate reductase (MDHAR) activity was stimulated at the third ripening stage. Conversely, the activities of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were enhanced only in 'Brigitta' and in 'Duke', respectively. BTH stimulated total polyphenols, flavonoid and anthocyanin accumulation in 'Brigitta' and in 'Duke' at the third and fourth ripening stages. In fully ripe berries, BTH enhanced the accumulation of delphinidins, cyanidins, petunidins and peonidins in 'Brigitta', while in 'Duke' it increased all classes of anthocyanidins, including malvidin. On the contrary, the relative proportion of the individual anthocyanins was only slightly affected by BTH treatment, mainly regarding delphinidin and malvidin at the third and fourth stage of ripening of 'Duke' and 'Brigitta', respectively. These results show that preharvest BTH application can positively impact on fruit bioactive compounds levels, affecting AsA recycling and content and increasing polyphenols accumulation in fruit, but partly depending on cv and ripening stage.

Comprehensive proteome and lysine acetylome analysis after artificial aging reveals the key acetylated proteins involved in wheat seed oxidative stress response and energy production

Lysine acetylation is a common post-translational modification of proteins within all organisms. However, quantitative acetylome characterization in wheat seed during aging in storage has not been reported. This study reports the first large-scale acetylome analysis of wheat seeds after artificial aging treatment, using the quantitative proteomic approach. In total, 11,002 acetylation sites, corresponding to 4262 acetylated proteins were identified, of which 1207 acetylated sites, representing 783 acetylated proteins, were significantly more or less acetylated after artificial aging. Functional analysis demonstrated that the majority of the acetylated proteins are closely involved with cellular and metabolic functions. In particular, key enzymes in the oxidative stress response and energy metabolism were significantly differentially acetylated and appear to be heavily involved in wheat seed aging. The acetylome analysis was verified by quantitative real-time PCR and enzyme activity determination. Lysine-acetylation results in a weaker oxidative stress response and lower energy production efficiency, resulting in the apoptosis of wheat seed cells, insufficient energy supply at the germination stage, and consequently, marked loss of seed vigor. PRACTICAL APPLICATIONS: It is known that the loss of protein function is an important reason for the decrease of seed vigor. Therefore, the change of protein function in the process of wheat seed aging was studied by proteome and lysine acetylome analysis technology. The results showed that the oxidation-reduction imbalance and the decrease of energy production efficiency of seeds were the important reasons for the decrease of their vigor. This will provide a new idea for green and safe storage of grain.

Controlled Atmosphere Improves the Quality, Antioxidant Activity and Phenolic Content of Yellow Peach during the Shelf Life

Controlled atmosphere (CA) has been demonstrated to maintain the shelf-life quality of fruits, but its effect on the antioxidant activities and phenolic content of yellow peach is not comprehensive. This study analyzed the role of CA on the quality of shelf period, phenolic content and antioxidant activity of "Jinxiu" yellow peach. Yellow peach was left under specific aeration conditions (3.5-4% CO2, 2-3% O2, 92-95.5% N2, 1 ± 0.5 °C) and the control (1 ± 0.5 °C) for 21 d, to observe changes in physiological parameters of the fruit during 10 d of the shelf life (25 ± 1 °C). The result showed that CA reduced the weight loss rate (WLR), decay rate (DR), and browning index (BI) of yellow peaches. Furthermore, the CA held a high level of total flavonoid content (TFC), total phenol content (TPC) and phenolic content in the fruit. Antioxidant analysis showed that polyphenol oxidase (PPO) enzyme activity was lower and free radical scavenging capacity (DPPH, ABTS, and FRAP) and antioxidant enzyme activities (POD and PAL) were higher in the CA group. Combining the results of significance analysis, correlation analysis, principal component analysis (PCA) and hierarchical cluster analysis (HCA) clearly identified the differences between the CA group and the control group. The results showed that the CA could maintain higher phenolic content and reduce the oxidation of yellow peach fruit and enhance fruit quality by affecting the antioxidant activities of yellow peach.

Impact of vanillin on postharvest disease control of apple

Apple fruits are susceptible to infection by postharvest fungal pathogens, which may cause fruit decay and severe economic losses. This study investigated the antifungal spectrum of vanillin against common decay pathogens of apple and explored the antifungal mechanisms of vanillin in vitro. In vivo experiments were carried out to evaluate the effects of vanillin on apple postharvest disease control and fruit quality. Moreover, the induced resistance mechanism of vanillin on apple fruit was preliminarily explored. The results showed that vanillin has broad-spectrum antifungal effects, especially on Alternaria alternata. Vanillin could significantly inhibit the growth rate, mycelium biomass, and spore germination of pathogenic fungi by increasing the cell membrane permeability and lipid peroxidation. Importantly, vanillin treatment reduced the incidence of apple decay caused by A. alternata and Penicillium expansum, and contributed to improve fruit quality. Further studies indicated that vanillin could induce elevation in the activities of defense-related enzymes in apple fruit, such as phenylalanine ammonia-lyase (PAL), chitinase (CHI) and β-1,3-glucanase (β-1,3-GA), and increase total phenols and flavonoids contents. Generally, these results suggest that vanillin may contribute to the induced resistance of apple fruits to pathogenic fungi. To conclude, the results of this research provide theoretical foundations for the application of vanillin in the control of apple postharvest decay caused by fungal pathogens.

Mitochondrial protein expression during sweet pepper (Capsicum annuum L.) fruit ripening: iTRAQ-based proteomic analysis and role of cytochrome c oxidase

The physiological process of fruit ripening is associated with the late developmental stages of plants in which mitochondrial organelles play an important role in the final success of this whole process. Thus, an isobaric tag for relative and absolute quantification (iTRAQ)-based analysis was used to quantify the mitochondrial proteome in pepper fruits in this study. Analysis of both green and red pepper fruits identified a total of 2284 proteins, of which 692 were found to be significantly more abundant in unripe green fruits as compared to red fruits, while 497 showed lower levels as the ripening process proceeded. Of the total number of proteins identified, 2253 (98,6%) were found to share orthologs with Arabidopsis thaliana. Proteomic analysis identified 163 proteins which were categorized as cell components, the major part assigned to cellular, intracellular space and other subcellular locations such as cytosol, plastids and, to a lesser extent, to mitochondria. Of the 224 mitochondrial proteins detected in pepper fruits, 78 and 48 were more abundant in green and red fruits, respectively. The majority of these proteins which displayed differential abundance in both fruit types were involved in the mitochondrial electron transport chain (mETC) and the tricarboxylic acid (TCA) cycle. The abundance levels of the proteins from both pathways were higher in green fruits, except for cytochrome c (CYC2), whose abundance was significantly higher in red fruits. We also investigated cytochrome c oxidase (COX) activity during pepper fruit ripening, as well as in the presence of molecules such as nitric oxide (NO) and hydrogen peroxide (H₂O₂), which promote thiol-based oxidative post-translational modifications (oxiPTMs). Thus, with the aid of in vitro assays, cytochrome c oxidase (COX) activity was found to be potentially inhibited by the PTMs nitration, S-nitrosation and carbonylation. According to protein abundance data, the final segment of the mETC appears to be a crucial locus with regard to fruit ripening, but also because in this location the biosynthesis of ascorbate, an antioxidant which plays a major role in the metabolism of pepper fruits, occurs.

Trehalose Regulates Starch, Sorbitol, and Energy Metabolism to Enhance Tolerance to Blue Mold of "Golden Delicious" Apple Fruit

The efficacy of trehalose on the lesion diameter of apples (cv. Golden Delicious) inoculated with Penicillium expansum was evaluated to screen the optimal concentration. The changes in gene expression and activity of the enzyme in starch, sorbitol, and energy metabolism were also investigated in apples after trehalose treatment. The results revealed that trehalose dipping reduced the lesion diameter of apples inoculated with P. expansum. Trehalose suppressed the activities and gene expressions of β-amylase, NAD-sorbitol dehydrogenase, and NADP-sorbitol dehydrogenase, whereas it decreased the sorbitol 6-phosphate dehydrogenase gene expression and amylose, amylopectin, total starch, and reducing sugar contents. Additionally, trehalose improved the gene expressions and activities of α-amylase, starch-branching enzymes, total amylase, H⁺-ATPase, and Ca²⁺-ATPase, as well as soluble sugar, adenosine triphosphate, and adenosine diphosphate contents and energy charge in apples. These findings imply that trehalose could induce tolerance to the blue mold of apple fruit by regulating starch, sorbitol, and energy metabolism.

Transcriptome sequencing and differential expression analysis of natural and BTH-treated wound healing in potato tubers (Solanum tuberosum L.)

Background

Wound healing is a representative phenomenon of potato tubers subjected to mechanical injuries. Our previous results found that benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) promoted the wound healing of potato tubers. However, the molecular mechanism related to inducible wound healing remains unknown.

Results

Transcriptomic evaluation of healing tissues from potato tubers at three stages, namely, 0 d (nonhealing), 5 d (wounded tubers healed for 5 d) and 5 d (BTH-treated tubers healed for 5 d) using RNA-Seq and differentially expressed genes (DEGs) analysis showed that more than 515 million high-quality reads were generated and a total of 7665 DEGs were enriched, and 16 of these DEGs were selected by qRT-PCR analysis to further confirm the RNA sequencing data. Gene ontology (GO) enrichment analysis indicated that the most highly DEGs were involved in metabolic and cellular processes, and KEGG enrichment analysis indicated that a large number of DEGs were associated with plant hormones, starch and sugar metabolism, fatty acid metabolism, phenylpropanoid biosynthesis and terpenoid skeleton biosynthesis. Furthermore, a few candidate transcription factors, including MYB, NAC and WRKY, and genes related to Ca²⁺-mediated signal transduction were also found to be differentially expressed during wound healing. Most of these enriched DEGs were upregulated after BTH treatment.

Conclusion

This comparative expression profile provided useful resources for studies of the molecular mechanism via these promising candidates involved in natural or elicitor-induced wound healing in potato tubers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08480-1.

ε-Poly-l-Lysine Enhances Fruit Disease Resistance in Postharvest Longans (Dimocarpus longan Lour.) by Modulating Energy Status and ATPase Activity

ε-poly-l-lysine (ε-PL) holds a strong antibacterial property and is widely used for food preservation. However, the application of ε-PL to enhance fruit disease resistance in postharvest longans (Dimocarpus longan Lour.) has not been explored. The objective of this study was to explore the impact of ε-PL treatment on disease occurrence and energy metabolism of longans infected with Phomopsis longanae Chi (P. longanae). It was found that, in comparison with P. longanae-inoculated longans, ε-PL could decrease the fruit disease index and adenosine monophosphate (AMP) content, increase the amounts of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and energy charge, and enhance the activities of adenosine triphosphatase (ATPase) (such as H⁺-, Mg²⁺-, and Ca²⁺-ATPase) in the mitochondria, protoplasm, and vacuole. The results suggest that the higher levels of ATPase activity and energy status played essential roles in disease resistance of postharvest longan fruit. Therefore, the ε-PL treatment can be used as a safe and efficient postharvest method to inhibit the disease occurrence of longan fruit during storage at room temperature.

Nitric Oxide Extends the Postharvest Life of Water Bamboo Shoots Partly by Maintaining Mitochondrial Structure and Energy Metabolism

Harvested water bamboo shoots can be stored for only a few days before they lose weight and become soft. Nitrogen oxide (NO) and modified atmosphere packaging (MAP) have previously been used to prolong horticultural crop storage. In the present study, we analyzed the joint effect of these two methods on extending the postharvest quality of water bamboo shoots. Water bamboo shoots were treated with (1) 30 μL L⁻¹ NO, (2) MAP, and (3) a combination of NO and MAP. The NO treatment delayed the softness and weight loss through maintaining the integrity of the mitochondrial ultrastructure and enhancing the ATP level by activating the expressions and activities of succinic dehydrogenase, malic acid dehydrogenase, and cytochrome oxidase. MAP improved the effect of NO on the mitochondrial energy metabolism. These results indicate that NO and MAP treatments are effective at suppressing the quality deterioration of water bamboo shoots, MAP improves the effect of NO in extending postharvest life, and NO may be the main effective factor in the combination of NO and MAP.

Cinnamaldehyde promotes the defense response in postharvest citrus fruit inoculated with Penicillium digitatum and Geotrichum citri-aurantii

Induced resistance in harvested fruit and vegetables is a superior strategy to reduce postharvest decay. In the present study, Cinnamaldehyde (CA) was applied to investigate for its induced resistance against Penicillium digitatum and Geotrichum citri-aurantii. The results showed that 5250 mg CA/L wax was effective concentration in inducing the resistance of citrus fruit to green mold and sour rot. Wax+ CA (WCA) reduced significantly green mold and sour rot incidences at different exposure times, with 24 h being the optimal exposure time. The host reactions under infection with different pathogens were similar. During initial exposure, treatment with 5250 mg CA/L wax enhanced significantly the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), β-1, 3-glucanase (GLU) and chitinase (CHT) in the presence of direct contact with the pathogen. Simultaneously, WCA induced an increase in total phenolic, flavanone and dihydroflavonol, flavone and flavonol, and lignin contents. Thus, our results suggest that treatment using 5250 mg CA/L wax can be applied early to control diseases by provoking response reactions in citrus fruit.

Effects of nitric oxide on the alleviation of postharvest disease induced by Penicillium italicum in navel orange fruits

The present study evaluated the effects of 15 μL L‐1 nitric oxide (NO) on the fruit defence response of ‘Newhall’ navel orange. The decay rate of NO‐treated navel orange fruits was significantly lower than that of control fruits during storage at 20 °C storage (P < 0.05). Treatment with NO suppressed the increase in disease incidence and lesion area in orange fruits inoculated with Penicillium italicum (P. italicum); significantly increased the activities of phenolic metabolism‐associated enzymes and pathogenesis‐related (PR) proteins, including polyphenoloxidase (PPO), phenylalanine ammonia‐lyase (PAL), β‐1,3‐glucanase (GLU) and chitinase (CHT); and enhanced the activities of key enzymes, including 4‐coumarate: CoA ligase (4CL), cinnamate‐4‐hydroxylase (C4H) and chalcone isomerase (CHI) in the phenylpropanoid pathway. The contents of total phenolics, flavonoids and lignin were also higher in NO‐treated fruits than in control fruits. The findings suggest that exogenous NO could induce disease resistance against P. italicum in navel orange fruits.

Sodium Hydrosulfide Induces Resistance Against Penicillium expansum in Apples by Regulating Hydrogen Peroxide and Nitric Oxide Activation of Phenylpropanoid Metabolism

As a multifunctional signaling molecule, hydrogen sulfide (H₂S) has been reported to induce plant responses to a variety of abiotic stresses. However, there are no reports on H₂S treatment inducing resistance in apples against Penicillium expansum, a biotic factor, and its possible mechanism of action. In this study, fumigating apples with 5 mM sodium hydrosulfide (NaHS), the exogenous donor of H₂S, for 12 h reduced the diameter of lesions in fruit colonized by P. expansum. NaHS treatment markedly promoted the synthesis of endogenous H₂S, hydrogen peroxide (H₂O₂), and nitrogen oxide (NO). In vivo NaHS treatment enhanced the activities of phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, p-coumarate:coenzyme A ligase isoenzymes, caffeoyl-CoA-O-methyltransferase, caffeic acid-O-methyltransferase, ferulic acid-5-hydroxylase, cinnamyl-CoA reductase, and cinnamyl-alcohol dehydrogenase. The treatment also facilitated the production of specific phenolic acids, such as cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, and sinapic acid; total phenolic compounds; p-coumaryl alcohol; coniferyl alcohol; sinapyl alcohol; and lignin. NaHS treatment induced resistance against P. expansum in apples through H₂O₂- and NO-mediated activation of phenylpropanoid metabolism.

The Role of Mitochondrial Energy Metabolism in Shaping the Quality of Highbush Blueberry Fruit During Storage in Ozone-Enriched Atmosphere

The aim of this study was to evaluate the effect of ozone treatment on the mitochondrial energy metabolism in blueberry fruit during storage as well as to determine the relationship between the activity of mitochondria and the antioxidative properties of ozonated fruit. Blueberry fruit was stored for 28 days at 4 °C and ozonated daily with gaseous ozone at the concentration of 15 mg L−1 for 30 min, every 12 h of storage. Research showed that ozonated fruit was characterized by higher activity of enzymes involved in oxidative phosphorylation (by 58.7% for SDH, 118.2% for CCO, and 78.16% for H+-ATPase after 7 days, respectively) than non-ozonated sample, which contributed to reduction of the loss of energy charge and ATP in the fruit during storage. Moreover, the increased activity of mitochondria led to the growth of mitochondrial ROS accumulation which, in turn, activated defense mechanisms against oxidative stress in the fruit. These metabolic responses might collectively contribute to increase the antioxidative properties of ozonated fruit and consequently to maintain a good quality of the fruit over a long period of storage.

Effect of benzothiadiazole treatment on quality and anthocyanin biosynthesis in plum fruit during storage at ambient temperature

BACKGROUND

Plums tend to experience a reduction in fruit quality due to ripening and they deteriorate quickly during storage at room temperature. Benzothiadiazole (BTH) is a plant elicitor capable of inducing disease resistance in many crops. In this study, the effect of BTH treatment on fruit ripening, fruit quality, and anthocyanin biosynthesis in 'Taoxingli' plum was investigated.

RESULTS

The results showed that BTH treatment could accelerate fruit ripening without affecting the incidence of fruit decay or the shelf life. Benzothiadiazole treatment improved the quality and consumer acceptability of 'Taoxingli' plums during storage by increasing the sweetness, red color formation, and the concentration of healthy antioxidant compounds. The BTH treatment could also effectively promote the biosynthesis of anthocyanin by enhancing the enzyme activities of phenylalanine ammonia-lyase (PAL), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and uridine diphosphate flavonoid 3-O-glucosyltransferase (UFGT) and up-regulating the gene expressions of PsPAL, PsCHI, PsDFR, PsANS, and PsUFGT during storage.

CONCLUSION

Benzothiadiazole treatment could be a potential postharvest technology for improving fruit quality and consumer acceptability in harvested plum fruit. © 2020 Society of Chemical Industry.

BTH Treatment Delays the Senescence of Postharvest Pitaya Fruit in Relation to Enhancing Antioxidant System and Phenylpropanoid Pathway

The plant resistance elicitor Benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) can enhance disease resistance of harvested fruit. Nonetheless, it is still unknown whether BTH plays a role in regulating fruit senescence. In this study, exogenous BTH treatment efficiently delayed the senescence of postharvest pitaya fruit with lower lipid peroxidation level. Furthermore, BTH-treated fruit exhibited lower hydrogen peroxide (H₂O₂) content, higher contents of reduced ascorbic acid (AsA) and reduced glutathione (GSH) levels and higher ratios of reduced to oxidized glutathione (GSH/GSSG) and ascorbic acid (AsA/DHA), as well as higher activities of ROS scavenging enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and glutathione reductase (GR) in comparison with control fruit. Moreover, BTH treatment enhanced the activities of phenylpropanoid pathway-related enzymes, including cinnamate-4-hydroxylase (C4H), phenylalanine ammonia-lyase (PAL) and 4-coumarate/coenzyme A ligase (4CL) and the levels of phenolics, flavonoids and lignin. In addition, BTH treatment upregulated the expression of HuSOD1/3/4, HuCAT2, HuAPX1/2 and HuPOD1/2/4 genes. These results suggested that application of BTH delayed the senescence of harvested pitaya fruit in relation to enhanced antioxidant system and phenylpropanoid pathway.

Isolation and comparative proteomic analysis of mitochondria from the pulp of ripening citrus fruit

Mitochondria are crucial for the production of primary and secondary metabolites, which largely determine the quality of fruit. However, a method for isolating high-quality mitochondria is currently not available in citrus fruit, preventing high-throughput characterization of mitochondrial functions. Here, based on differential and discontinuous Percoll density gradient centrifugation, we devised a universal protocol for isolating mitochondria from the pulp of four major citrus species, including satsuma mandarin, ponkan mandarin, sweet orange, and pummelo. Western blot analysis and microscopy confirmed the high purity and intactness of the isolated mitochondria. By using this protocol coupled with a label-free proteomic approach, a total of 3353 nonredundant proteins were identified. Comparison of the four mitochondrial proteomes revealed that the proteins commonly detected in all proteomes participate in several typical metabolic pathways (such as tricarboxylic acid cycle, pyruvate metabolism, and oxidative phosphorylation) and pathways closely related to fruit quality (such as γ-aminobutyric acid (GABA) shunt, ascorbate metabolism, and biosynthesis of secondary metabolites). In addition, differentially abundant proteins (DAPs) between different types of species were also identified; these were found to be mainly involved in fatty acid and amino acid metabolism and were further confirmed to be localized to the mitochondria by subcellular localization analysis. In summary, the proposed protocol for the isolation of highly pure mitochondria from different citrus fruits may be used to obtain high-coverage mitochondrial proteomes, which can help to establish the association between mitochondrial metabolism and fruit storability or quality characteristics of different species and lay the foundation for discovering novel functions of mitochondria in plants.

Effect of Ozonation Process on the Energy Metabolism in Raspberry Fruit During Storage at Room Temperature

The major aim of this research was to investigate the effect of ozone treatment on the energy metabolism in raspberry fruit during storage at room temperature. Raspberries were ozonated with an ozone concentration of 8–10 mg L−1, for 30 min, every 12 h of storage at room temperature for 72 h. The results indicated that ozone treatment significantly enhanced the activities of mitochondrial respiratory enzymes, such as succinate dehydrogenase, cytochrome C oxidase, and H+-ATPase, which contributed to maintain the high level of ATP and energy charge in fruit during storage. Moreover, the energy metabolism in mitochondria was closely correlated with the antioxidant potential of raspberry fruit. This study has given an experimental evidence that ozonation procedure in proposed process conditions significantly affects the mitochondrial respiratory system leading to maintain the high quality of the fruit over a long period of storage at room temperature.

Roles of calcium-dependent protein kinases mediated reactive oxygen species homeostasis in inducing resistance of apples by acibenzolar-S-methyl

This study was carried out to investigate the effect of acibenzolar-S-methyl (ASM) and ethylenebis (oxyethylenenitrilo) tetraacetic acid (EGTA) treatments on calcium-dependent protein kinases (CDPKs) and reactive oxygen species (ROS) metabolism in apples. Postharvest ASM treatment increased H₂O₂ content, reduced glutathione and ascorbic acid contents, and NADPH oxidase, peroxidase, ascorbate peroxidase, superoxide dismutase and glutathione reductase activities and retarded catalase activity and MdCAT expression in apples. ASM treatment enhanced MdSOD, MdPOD, MdAPX, MdGR, MdCDPK1, MdCDPK4, MdCDPK5, MdCDPK7, and MdCDPK21 expressions in apples. However, EGTA + ASM treatments suppressed H₂O₂, glutathione and ascorbic acid contents, NADPH oxidase, peroxidase, superoxide dismutase, ascorbate peroxidase and glutathione reductase activities. EGTA + ASM treatments suppressed the selected genes expressions in ROS metabolism and CDPKs, but up-regulated MdCAT expression in apples. These findings suggest that CDPKs play a vital role in regulating ROS metabolism and involve in inducing resistance in apples by ASM.

The role of signal production and transduction in induced resistance of harvested fruits and vegetables

Postharvest diseases are the primary reason causing postharvest loss of fruits and vegetables. Although fungicides show an effective way to control postharvest diseases, the use of fungicides is gradually being restricted due to safety, environmental pollution, and resistance development in the pathogen. Induced resistance is a new strategy to control postharvest diseases by eliciting immune activity in fruits and vegetables with exogenous physical, chemical, and biological elicitors. After being stimulated by elicitors, fruits and vegetables respond immediately against pathogens. This process is actually a continuous signal transduction, including the generation, transduction, and interaction of signal molecules. Each step of response can lead to corresponding physiological functions, and ultimately induce disease resistance by upregulating the expression of disease resistance genes and activating a variety of metabolic pathways. Signal molecules not only mediate defense response alone, but also interact with other signal transduction pathways to regulate the disease resistance response. Among various signal molecules, the second messenger (reactive oxygen species, nitric oxide, calcium ions) and plant hormones (salicylic acid, jasmonic acid, ethylene, and abscisic acid) play an important role in induced resistance. This article summarizes and reviews the research progress of induced resistance in recent years, and expounds the role of the above-mentioned signal molecules in induced resistance of harvested fruits and vegetables, and prospects for future research.

Influences of postharvest ATP treatment on storage quality and enzyme activity in sucrose metabolism of Malus domestica

The respiratory metabolism of apples remains vigorous after harvest, which can accelerate the consumption of sugar, organic acid, and other substances, thus leading to a decline in quality. The influence of postharvest ATP treatment on the changes of quality parameters and sucrose metabolism-related enzyme activity in apples was investigated in this study. The results showed that applying ATP effectively repressed the respiratory rate and weight loss and maintained higher levels of soluble solids content and flesh firmness in apples. In addition, ATP treatment enhanced succinate dehydrogenase, cytochrome oxidase, sucrose phosphate synthase, and sucrose synthase synthesis activities and reduced neutral invertase, acid invertase, and sucrose synthase cleavage activities in apples. These findings suggest that applying ATP after harvest could improve the internal quality of apples by suppressing the respiratory rate and modulating sucrose metabolism.