•Acquiring purified tonoplast from apple fruit using an iodixanol step gradient protocol•Characterizing the dynamic alterations of the tonoplast proteome during senescence process of apple fruit•Identifying a total of 22 tonoplast proteins with differential levels of abundance during storage periods•Providing novel insight into understanding the role of tonoplast on fruit senescenceThe vacuole is by far the largest multifunctional organelle in fruits and plays a functional role in fruit development and fruit quality. Despite its significance, little information exists pertaining to the role of the vacuolar membrane (tonoplast) in the process of fruit senescence. In the present study, an iTRAQ-based quantitative proteomic approach was used to characterize the dynamic alterations in the tonoplast proteome during fruit senescence. Tonoplasts were purified from apple fruit at various stages of senescence using an iodixanol step gradient protocol. A total of 345 tonoplast-related proteins were identified with diverse functions such as transporters and proton pumps, signal transduction, membrane fusion or vesicle trafficking, cellular metabolic process, defense response, protein folding and degradation, and cytoskeleton. Changes in protein abundance during storage were characterized for the identified proteins. A total of 22 proteins displayed differential levels of abundance during storage. The senescence-related tonoplast proteins mostly function in the transportation of metabolites, signal transduction, membrane trafficking, and stress response. RT-qPCR analysis was used to quantify the level of expression of nine genes encoding some of the differentially abundant proteins. The results of this study provide new information regarding the function of the tonoplast during fruit senescence.Biological significanceStudies on the postharvest physiology and biochemistry of apple fruit have been conducted for several decades. Little proteomic information is available, however, pertaining to the role of the vacuole in fruit ripening and senescence. In the present study, an iTRAQ-based quantitative proteomic analysis was conducted on tonoplasts isolated from apple fruit in order to gain a global view of alterations in the tonoplast proteome during fruit senescence. The information obtained in the present study not only provides basic information about the tonoplast proteome in apple fruit but also characterized the quantitative changes that occur in the abundance of tonoplast proteins during the course of fruit senescence. This study provides a deeper insight into the cellular functions of the vacuole during fruit senescence that can serve as a basis for the development of future biotechnological strategies for the improvement of fruit quality.Graphical abstract

Cinnamic acid (CA) is an organic acid and is widely used in food industry as a common food additive. Previous studies showed that CA has the antimicrobial activity in vitro, but little is known about the effect of CA on controlling the fruit decay in vivo. In present study, we showed that application of CA was significantly effective on controlling the gray mold of table grape caused by Botrytis cinerea. CA can directly inhibit the mycelial growth of B. cinerea on potato dextrose agar plates. The mechanisms by which CA inhibited fungal growth were assayed by staining the spores with fluorescent dyes propidium iodide and 7-dichlorodihydrofluorescein diacetate, respectively. The results indicated that CA can damage the integrity of plasma membrane and induce the intracellular reactive oxygen species level of B. cinerea which were responsible for the reduction of growth rate. Meanwhile, CA treatment significantly stimulated the activities of peroxidase and polyphenol oxidase which were closely related to the resistance of plant. Taken together, this study suggested that CA was effective on controlling the gray mold of table grape in postharvest period by inhibiting the growth of pathogen and inducing the resistance of host.

•Observed NO could inhibit the germination of P. expansum spores•Identified ten expressed proteins of P. expansum in response to exogenous NO•Evaluated the expression of three genes associated with the identified proteins•Speculated functional mode of NO inhibiting P. expansumPenicillium expansum is an important fungal pathogen, which causes blue mold rot in various fruits and produces a mycotoxin (patulin) with potential damage to public health. Here, we found that nitric oxide (NO) donor could significantly inhibit germinability of P. expansum spores, resulting in lower virulence to apple fruit. Based on two dimension electrophoresis (2-DE) and mass spectrometry (MS) analysis, we identified ten differentially expressed proteins in response to exogenous NO in P. expansum. Among of them, five proteins, such as glutamine synthetase (GS), amidohydrolase, nitrilases, nitric oxide dioxygenase (NOD) and heat shock protein 70, were up-regulated. Others including tetratricopeptide repeat domain, UDP-N-acetylglucosamine pyrophosphorylase, enolase (Eno), heat shock protein 60 and K homology RNA-binding domain were down-regulated. The expression of three genes associated with the identified proteins (GS, NOD, and Eno) was evaluated at the mRNA level by RT-PCR. Our results provide the novel evidence for understanding the mechanism, by which NO regulates growth of P. expansum and its virulence.Biological significanceCrop diseases caused by fungal pathogens lead to huge economic losses every year in the world. Application of chemical fungicides to control diseases brings the concern about food and environmental safety. Screening new antimicrobial compounds and exploring involved mechanisms have great significance to development of new disease management strategies. Nitric oxide (NO), as an important intracellular signaling molecule, has been proved to be involved in many physiological processes and defense responses during plant–pathogen interactions. In this study, we firstly found that NO at high concentration could distinctly delay spore germination and significantly reduce virulence of P. expansum to fruit host, identified some important proteins in response to NO stress and characterized the functions of these proteins. These results provide novel evidence for understanding the mechanism of NO regulating virulence of the fungal pathogen, but are beneficial for screening new targets of antifungal compounds.

•TFP increased the viability of C. guilliermondii under H2O2 stress.•29 DRM protein spots differentially expressed in response to TFP were identified.•TFP alleviated oxidative damage to cellular proteins.•Ca2 +–CaM regulates the viability via acting on DRM proteins.Reactive oxygen species (ROS) play a vital role in reducing viability of yeast cells. The Ca2 +–CaM signaling pathways are involved in regulating the intracellular ROS level in yeast cells under stress. Detergent resistant membranes (DRMs), the sterol-rich microdomains, participate in a wide range of cellular processes including growth, trafficking and death in yeast cells. In the present study, we found that Trifluoperazine (TFP), an antagonist of CaM, could increase the viability of Candida guilliermondii cells under H2O2 stress. Based on comparative analysis of DRM sub proteomics, a total number of 29 differentially expressed protein spots were identified, among which 8 protein spots belong to the electron transport chain and 7 protein spots belong to transporters. It is suggested that TFP treatment could modulate the intracellular ROS generation in yeast cells. We additionally ascertained that TFP treatment could effectively alleviate the ROS accumulation and protein damage in C. guilliermondii cells under H2O2 stress, via investigating the intracellular ROS levels and protein oxidative damage in yeast cells. These findings firstly revealed that the Ca2 +–CaM signaling pathway is related to the viability of yeast cells under H2O2 stress, and provide novel evidences for exploring Ca2 +–CaM's role in regulating this viability via acting on DRM proteins.Biological significanceDetergent-resistant membranes (DRMs), which are more resistant to extraction with cold non-ionic detergents, have been considered the functional microdomains in the plasma membrane. In yeast, DRMs are involved in a wide range of additional cellular processes including cell growth and death. The Ca2 +–CaM signaling pathways could regulate the stress tolerance of yeast cells by modulating the intracellular ROS generation. In this study, we found that trifluoperazine (TFP), a calmodulin antagonist, could increase the viability of C. guilliermondii under H2O2 stress. Based on comparative analysis of DRM sub proteomics, electron transport chain proteins and transporters were identified to be associated with the Ca2 +–CaM transduction. We proved that TFP treatment decreases the intracellular ROS accumulation and alleviates oxidative damage to cellular proteins. These results ascertain that Ca2 +–CaM is involved in regulating the viability of C. guilliermondii under oxidative stress via acting on the DRM proteins.

•Controlled atmosphere (CA) could maintain higher contents of sucrose, fructose and glucose in apple fruit during the storage.•Six genes encoding key enzymes involved in sugar metabolism in apple fruit were cloned.•Effects of CA on gene expression and enzyme activities in fruit were investigated.Sugars are essential contributors to fruit flavour. Controlled atmosphere (CA) storage has been proved to be beneficial for maintaining harvested fruit quality. To explore regulatory mechanism of sugar metabolism in fruit stored in CA condition, we cloned several genes, encoding key enzymes, involved in sugar metabolism in apple fruit, and analyzed sugar contents, along with gene expression and enzyme activities in fruits stored in air and CA. The results indicated that CA could maintain higher contents of sugars, including sucrose, fructose and glucose. Expression levels of key genes, such as sucrose synthase (SS), sucrose phosphate synthase (SPS), fructokinase (FK) and hexokinase (HK), were shown to be correlated with the corresponding enzyme activities. We found that activities of neutral invertase (NI), vacuolar invertase (VI), FK and HK were inhibited, but SPS activity was promoted in apple fruit stored in CA, suggesting that CA storage could enhance sucrose synthesis and delay hydrolysis of sucrose and hexose. These findings provided molecular evidence to explain why higher sugar levels in harvested fruit are maintained under CA storage.

Senescence is a vital aspect of fruit life cycles, and directly affects fruit quality and resistance to pathogens. Reactive oxygen species (ROS), as the primary mediators of oxidative damage in plants, are involved in senescence. Mitochondria are the main ROS and free radical source. Oxidative damage to mitochondrial proteins caused by ROS is implicated in the process of senescence, and a number of senescence-related disorders in a variety of organisms. However, the specific sites of ROS generation in mitochondria remain largely unknown. Recent discoveries have ascertained that fruit senescence is greatly related to ROS and incidental oxidative damage of mitochondrial protein. Special mitochondrial proteins involved in fruit senescence have been identified as the targets of ROS. We focus in discussion on our recent advances in exploring the mechanisms of how ROS regulate fruit senescence and fungal pathogenicity.

Reactive oxygen species (ROS) play a vital role in reducing the viability of invading pathogens during plant-pathogen interactions. To understand how oxidative stress caused by ROS reduces cell viability, it is important to identify the proteins affected by ROS. In the present study, we investigated the changes in the expression of proteins from the outer and inner membrane fractions in Pseudomonas syringae pv tomato DC3000 under oxidative stress through membrane subproteomics. A total number of 17 differentially expressed proteins from the outer and inner membrane fractions were identified, among which 11 proteins belong to transporters, such as porins and ABC transporters. Their abundance was all decreased under oxidative stress, indicating that transporters are likely to be affected by oxidative stress. The function of two identified transporters was further characterized by constructing their gene mutant and overexpression strains. We found that mutation of one transporter gene PSPTO_1720 rendered Pseudomonas more sensitive to oxidative stress, whereas overexpression of this gene made the strain more resistant. By comparison, the mutant and overexpression strains of another transporter gene PSPTO_2152 exhibited the same sensitivity to oxidative stress compared with the wild-type. Our data suggest that oxidative stress reduces the viability of bacterial cells by acting on special transporters.

Botrytis cinerea causes gray mold rot on over 200 plant species worldwide, resulting in great economic loss every year. Cooperation of proteins secreted by B. cinerea plays an important role in its successful infection to host plants. The ambient pH, as one of the most important environmental parameters, can regulate expression of secreted proteins in various fungal pathogens. In the present study, we mainly investigated the effect of ambient pH on secretome of B. cinerea strain B05.10 with a comparative proteomic method based on 2-DE. Distinct differences in secretome of B. cinerea were found between pH 4 and 6 treatments, and 47 differential spots, corresponding to 21 unique proteins, were identified using MALDI-TOF/TOF. At pH 4, more proteins related to proteolysis were induced, whereas most of up-accumulated proteins were cell wall degrading enzymes at pH 6. Analysis of gene expression using quantitative real-time PCR suggests that production of most of these proteins was regulated at the level of transcription. These findings indicate that B. cinerea can adjust protein profile of secretome responding to different ambient pH values and provide evidence to deeply understand the complicated infecting mechanisms of B. cinerea on a wide range of plant hosts.

In this article, we investigated the effect of exogenous calcium on improving viability of Debaryomyces hansenii and Pichia membranaefaciens under heat stress, and evaluated the role of calcium in reducing oxidant damage of proteins in the yeast cells. The results indicated that high concentration of exogenous calcium in culture medium was beneficial for enhancing the tolerance of the biocontrol yeasts to heat stress. The possible mechanism of calcium improving the viability of yeasts was attributed to enhancement of antioxidant enzyme activities, decrease in ROS accumulation and reduction of oxidative damage of intracellular protein in yeast cells under heat stress. D. hansenii is more sensitive to calcium as compared to P. membranaefaciens. Our results suggest that application of exogenous calcium combined with biocontrol yeasts is a practical approach for the control of postharvest disease in fruit.

The differences between chitosan (350 kDa) and oligochitosan (6 kDa) in inhibitory effect on phytopathogenic fungi and on decay control were investigated. Both chitosan and oligochitosan strongly inhibited spore germination and mycelial growth of Alternaria kikuchiana Tanaka and Physalospora piricola Nose. Relatively, chitosan and oligochitosan showed more obvious inhibitory effect on mycelial growth than spore germination. Although oligochitosan had better inhibitory effects on fungal pathogenicity in vitro, chitosan was more effective on disease control in pear fruit stored at 25 °C. When treated with oligochitosan, pear fruit increased the activities of chitinase (CHI) and β-1,3-glucanase. Differently, chitosan treatment significantly increased peroxidase (POD) activity of pear fruit. These results suggested that chitosan and oligochitosan triggered different mechanism for pathogenicity inhibition and disease control.

Spore germination is the first step for fungal pathogens to infect host plants. The pH value, as one of the most important environmental parameters, has critical influence on spore germination. In this study, effects of ambient pH on spore germination were determined by culturing spores of Penicillium expansum in medium with pH values at 2.0, 5.0 and 8.0, and involved mechanisms were further investigated through methods of comparative proteomics. The results demonstrated that spore germination of P. expansum was obviously inhibited at pH 2.0 and 8.0. Using quadrupole time-of-flight tandem mass spectrometer, 34 proteins with significant changes in abundance were identified. Among them, 17 proteins were related to protein synthesis and folding, and most of them were down-regulated at pH 2.0 and 8.0. Accordingly, lower content of total soluble proteins and higher ratio of aggregated proteins were observed in spores at pH 2.0 and 8.0. In addition, it was found that ambient pH could affect intracellular pH and ATP level of P. expansum spores. These findings indicated that ambient pH might affect spore germination of P. expansum by changing intracellular pH and regulating protein expression. Further, impairing synthesis and folding of proteins might be one of the main reasons.

Peach fruit (Prunuspersica L. cv. Beijing 33) did not show symptoms of chilling injury in 0 °C-Air or 0 °C-CA, but did in 5 °C-Air after 21 d. The mechanisms by which 0 °C storage could activate chilling tolerance of peach fruit were investigated by analysing characteristics of plasma membrane. We found that peach fruit stored in 0 °C-Air and 0 °C-CA had much higher linolenic acid content and unsaturation degree of plasma membrane than did that in 5 °C-Air. In addition, the fruits stored in 0 °C-CA showed a higher membrane fluidity and membrane integrity than did that in 0 °C-Air, which was related to the accumulation of N-acylphosphatidylethanolamine (NAPE) of peach fruits stored in 0 °C-CA. Based on these results, it appears that a higher unsaturation degree of membrane lipid and NAPE accumulation are beneficial for maintaining membrane fluidity, leading to an enhanced tolerance of peach fruit to chilling stress.

Proteome patterns in peach fruit (Prunus persica L.) stored at different low temperatures were examined in order to gain a better understanding why peach fruit is less prone to chilling injury when stored at 0°C than at 5°C. Some differently expressed proteins in peach fruit stored at 0 and 5°C were identified using electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Among these proteins, four membrane stability related proteins, i.e., enolase, temperature-induced lipocalin, major allergen Pru p 1, and type II SK2 dehydrin were enhanced, but three proteins related to phenolic compounds metabolization, cinnamyl-alcohol dehydrogenase 5, cinnamyl-alcohol dehydrogenase 1, and chorismate mutase, were repressed in peach fruit at 0°C as compared to that at 5°C. The abundance of glucose-6-phosphate dehydrogenase, NADP-dependent isocitrate dehydrogenase, and NADP-denpendent malic enzyme, which catalyze the reactions during sugar metabolism and energy pathways, was found to decrease in peach fruit stored at 0°C. In addition, our data revealed that low temperature of 0°C might regulate the endogenous H2O2 level, resulting in activating the transcriptional level of genes encoding the proteins related to membrane stability. These results provide a comprehensive knowledge to understand the mechanisms by which peach fruit stored at 0°C showed a higher chilling tolerance than that at 5°C.

The antifungal activity of silicon (Si) on Penicillium digitatum, and the possible action mode involved were investigated. Spore germination, germ tube elongation, and mycelial growth of P. digitatum were strongly inhibited by Si in the form of sodium silicate. Using propidium iodide (PI) stain combined with fluorescent microscopy, it was found that the plasma membrane of Si-treated P. digitatum spores was obviously damaged, and the leakage of protein and sugar was significantly higher in Si-treated mycelia than that of control. These findings suggest that the damage on plasma membrane of P. digitatum played a crucial role in the antifungal effect of Si. Moreover, Si was effective in controlling green mold caused by P. digitatum in citrus fruit. These results have a beneficial impact on the application of Si in the control of postharvest diseases.

Oxidative damage to mitochondria caused by reactive oxygen species (ROS) has been implicated in the process of senescence as well as a number of senescence-related disorders in a variety of organisms. Whereas mitochondrial DNA was shown to be oxidatively modified during cellular senescence, mitochondrial protein oxidation is not well-understood. With the use of high-resolution, two-dimensional gel electrophoresis coupled with immunoblotting, we show here that protein carbonylation, a widely used marker of protein oxidation, increased in mitochondria during the senescence of peach fruit. Specific mitochondrial proteins including outer membrane transporter (voltage-dependent anion-selective channel, VDAC), tricarboxylic acid cycle enzymes (malate dehydrogenase and aconitase), and antioxidant proteins (manganese superoxide dismutase, MnSOD) were found as the targets. The oxidative modification was concomitant with a change of VDAC function and loss of catalytic activity of malate dehydrogenase and MnSOD, which in turn facilitated the release of superoxide radicals in mitochondria. Reduction of ROS content by lowering the environmental temperature prevented the accumulation of protein carbonylation in mitochondria and retarded fruit senescence, whereas treatment of fruit with H2O2 had the opposite effect. Our data suggest that oxidative damage of specific mitochondrial proteins may be responsible for impairment of mitochondrial function, thus, leading to fruit senescence. Proteomics analysis of mitochondrial redox proteins provides considerable information on the molecular mechanisms involved in the progression of fruit senescence.

The quality and physiological changes were determined in peach (Prunus persica L. cv. Jiubao) fruits in low temperature storage with or without methyl jasmonate (MeJA) treatment. Peach fruits stored for 3 weeks at 5 °C and following 3 d shelf life intervals at 20 °C appeared chilling injury (CI) symptom, expressed as flesh browning. MeJA treatment decreased the CI index, which was possibly attributed to higher activity of peroxidase and lower content of phenolic compounds than that without MeJA treatment. Moreover, MeJA treatment not only enhanced the rate of SSC/TA in peach fruits by mainly restraining the decrease of the SSC in peach, but also affected the degradation of cell wall, perhaps by regulation of cell wall modifying enzymes and the calcium content in cell wall of flesh. The results suggested that MeJA treatment was beneficial for maintaining quality owing to reducing chilling injury of peach fruits under low temperature stress.

The objective of this present research is to study the biological basis of browning in peach fruit during storage at low temperatures. After being immersed in 0 or 2mmol·L−1 salicylic acid (SA) aqueous solution for 10 min, peach fruit (Prunus persica L. cv. Hongtao) were stored at 10°C, 5°C or 0°C with or without shelf life at 25°C. During storage, the progress of browning, lipid peroxidation, phenol content, activities of polyphenol oxidase (PPO, E.C. 1.14.18.1) and guaiacol peroxidase (POD, EC 1.11.1.7), redox state of ascorbate and glutathione, as well as the content, location and metabolism of hydrogen peroxide (H2O2) in the fruit were examined. The results indicated that a decrease in H2O2 content was correlated with browning, whereas phenol content and activities of PPO and POD were not correlated with the change in H2O2 content. Moreover, H2O2 content was influenced by different responses of antioxidants at different storage conditions. It was concluded that the main effect of H2O2 on browning was to regulate its appearance and development as a signal molecule, and lower H2O2 content was beneficial to browning.

Survivals of Cryptococcus laurentii and Pichia membranaefaciens in liquid formulations with sugar protectants (trehalose and galactose) and L-ascorbic acid (Vc) were investigated during storage at 4°C and 25°C. When galactose or trehalose was used alone as protectant, C. laurentii maintained relatively high viability in potassium phosphate buffer. Addition of Vc to trehalose improved its protective effect. P. membranaefaciens maintained viability >60% after 90 days at 4°C when 5% galactose served as a protectant, and its combination with Vc was the most effective at maintaining viability. Moreover, liquid formulation kept higher viability of the two yeasts at 4°C than at 25°C. Biocontrol efficiency of the two yeasts was maintained after formulation and storage. The results indicate that trehalose is considered as a suitable protectant for liquid formulation of C. laurentii, while galactose is better for P. membranaefaciens. Combining Vc with the sugars improves the protective efficiency.

The effects of preharvest chitosan spray (PCS) or/and postharvest chitosan coating (PCC) treatments on the quality and physiological response of table grape fruit stored at 20 or 0 °C was evaluated, respectively. PCS/PCC treatment showed the best control effect on decay. PCC or PCS/PCC treatment significantly decreased the weight loss of fruit stored at 20 °C. Additionally, all chitosan treatments inhibited the increase in rate of soluble solid content to titratable acid in fruit, stored at 20 °C, while enhancing the rate at 0 °C and affecting the content of total phenolic compounds in the fruit. Furthermore, the activities of superoxide dismutase decreased in all chitosan treatments and PCS or/and PCC treatments also changed the activities of polyphenol oxidase, peroxidase and phenylalanine ammonia-lyase. The results indicated the beneficial effect of chitosan by preharvest spray and/or postharvest coating on fruit quality and resistance to fruit decay.

Physiological and biochemical responses in peach fruit (Prunus persica L.) cv. ‘Bayuecui’ to two concentrations (1 and 5 mM) of oxalic acid treatment were studied during storage at room temperature (25 °C). Slower relative leakage rate, higher flesh firmness, lower respiration, increased activities of antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT; ascorbate peroxidase, APX) and polyphenol oxidase (PPO), and a decreased lipoxygenase (LOX) activity in treated fruit were observed as compared with the control. Moreover, significant decreases in the production of active oxygen species (AOS) (superoxide, O2- hydrogen peroxide, H2O2) and lipid peroxidation in treated fruit were found at the later time of storage. The effects of oxalic acid could therefore contribute to maintaining the membrane integrity and delaying the fruit ripening process. Increased activities of POD, SOD, and PPO might also possibly be of benefit to disease resistance during storage.

Litchi (Litchi chinensis Sonn.) fruit, cv. Huaizhi, was treated with 2 and 4 mM oxalic acid and stored at room temperature to investigate the effect of oxalic acid on pericarp browning. The results showed that the pericarp browning indices of the fruit, treated with both oxalic acid concentrations, were significantly lower than that of the control, due to increase of membrane integrity, inhibition of anthocyanin degradation, decline of oxidation, and maintanance of relatively low peroxidase activity in the fruit during storage. It appears that application of oxalic acid can effectively control the pericarp browning of litchi fruit during postharvest storage.

Litchi (Litchi chinensis Sonn. cv Heiye) fruit were stored in air, modified atmosphere packaging (MAP) and controlled atmospheres (CA) at 3 °C to determine the effects of different O2 and CO2 atmospheres on physiology, quality and decay during the storage periods. The results indicated that CA conditions were more effective in reducing total phenol content, delaying anthocyanidin decomposition, preventing pericarp browning, and decreasing fruit decay in comparison with MAP treatment. Polyphenol oxidase (PPO), peroxidase (POD), anthocyanin and total phenols were involved in cellular browning. High O2 treatment significantly limited ethanol production of litchi flesh in the early period of storage. The fruit stored in CA conditions for 42 days maintained good quality without any off-flavour.

Peach fruits (Amygdalus persica cv. Okubao) were stored in air, controlled atmospheres (CA) of 5% O2 plus 5% CO2, or CA with high O2 concentration (70% O2 plus 0% CO2 for 15 days, then in CA with 5% O2 plus 5% CO2) at 0 °C, to determine the effects of different O2 and CO2 atmospheres on the activities of lipoxygenase (LOX), peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), as well as malondialdehyde (MDA) content and membrane integrity during storage periods with or without 3 days of post-storage ripening at 20 °C. SOD, CAT and POD activities of the fruits stored in air markedly decreased during the first 30 days of storage, while LOX activity increased after 15 days. CA (5% O2 plus 5% CO2) reduced chilling injury, and delayed the reduction of SOD, CAT and POD activities compared to the control. CA with high O2 treatment induced SOD and CAT activities and maintained membrane integrity, but no significant effect on alleviating chilling injury was found compared to CA storage. The results indicated that the decrease of SOD and CAT might contribute to the development of chilling injury in peach fruits.

The role of exogenous salicylic acid (SA) in regulating an antioxidative defense response of sweet cherry (Prunus avium L. cv. Hongdeng) fruit inoculated with Penicillium expansum was investigated by immunodetection of carbonylated proteins. After inoculation with P. expansum, carbonylated proteins accumulated to a lesser extent in SA-treated fruit than in control fruit, ranging from molecular mass 29–45 kDa. Higher activities of catalase (CAT), glutathione peroxidase (GPX), chitinase and β-1,3-glucanase were observed in SA-treated fruit. Similarly, the expressions of CAT, GPX and β-1,3-glucanase genes were also stimulated by SA treatment. Moreover, 2 mM SA did not inhibit P. expansum growth in vitro. These results indicate that SA activated antioxidant defense responses of sweet cherry fruit, which may play a role in the resistance against P. expansum.

The effects of chitosan on gray mould and blue mould caused by Botrytis cinerea and Penicillium expansum in tomato fruit stored at 25 and 2 °C, respectively, were investigated. Chitosan provided an effective control of both diseases of tomato fruit stored at 25 and 2 °C. Chitosan strongly inhibited spore germination, germ tube elongation, and mycelial growth of B. cinerea and P. expansum in vitro, and damaged the plasma membranes of spores of both pathogens. Chitosan treatment induced a significant increase in the activities of polyphenoloxidase (PPO), peroxidase (POD), and enhanced the content of phenolic compounds in tomato fruit. These findings suggest that the effects of chitosan on gray mould and blue mould in tomato fruit may be associated with the direct fungitoxic property against the pathogens, and the elicitation of biochemical defense responses in fruit.

•Gene rho3 encoding small GTPase Rho3 was deleted in Botrytis cinerea.•Growth, conidiation, and appressorium formation are suppressed in Δrho3 mutants.•Δrho3 mutants show reduced virulence in both leaves and fruit.•Rho3 is related to mitochondria distribution and intracellular ROS generation.•Rho3 regulates polarized growth, conidiation, appressorium formation and virulence.Small GTPases of the Rho family play an important role in regulating biological processes in fungi. In this study, we mainly investigated the biological functions of Rho3 in Botrytis cinerea, and found that deletion of the rho3 from B. cinerea significantly suppressed vegetative growth and conidiation, reduced appressorium formation and decreased virulence. Microscopy analysis revealed that the distance between septa was increased in the Δrho3 mutant. In addition, mitochondria were suggested to be the main sources of intracellular reactive oxygen species (ROS) in B. cinerea based on dual staining with 2′,7′-dichlorodihydrofluorescein diacetate and MitoTracker orange. The Δrho3 mutant showed less accumulation of ROS in the hyphae tips compared to the WT strain of B. cinerea. These results provide the novel evidence to ascertain the function of small GTPase Rho3 in regulating growth, conidiation and virulence of B. cinerea.

•We review the molecular characterization of fungal postharvest virulence factors.•Future research lines in fruit-pathogen interaction studies have been identified.•Implementation of omics technologies will make an impact on fruit-pathogen studies.Fruit losses during postharvest storage and handling due to pathogen infections are one of the major problems in the global food chain supply. The application of chemical fungicides to control diseases is currently limited by legislation in some countries and also raises concerns about food and environmental safety. Exploring molecular aspects of pathogen-fruit interactions therefore has biological and economic significance as a means to help develop rational alternatives for disease control. In this review we present the current knowledge of molecular aspects in pathogen-fruit interactions, addressing the following topics: the application of new “omics” technologies for studying these interactions; the molecular mechanisms of fungal pathogen attack; the regulation of virulence by exogenous factors; and, finally, fruit defense mechanisms.

Mango fruit (Mangifera indica L. cv. Zill) were dipped in 5 mM oxalic acid solution for 10 min at 25 °C to investigate effects on ripening and decay incidence during storage at room temperature (25 °C). The results showed that oxalic acid treatment delayed fruit ripening and reduced fruit decay incidence compared to the control. It was suggested that the physiological effect of oxalic acid in decreasing ethylene production was an important contributor to delaying the ripening process. Oxalic acid treatment might be a promising method for postharvest storage of mango fruit.

The effects of brassinosteroids (BRs) against blue mould rot caused by Penicillium expansum and on senescence of harvested jujube fruit were investigated. Brassinosteroids at a concentration of 5 μM effectively inhibited development of blue mould rot and enhanced the activities of defense-related enzymes, such as phenylalanine ammonia-lyase, polyphenoloxidase, catalase and superoxide dismutase. However, BRs did not have direct antimicrobial activity against P. expansum in vitro. BRs significantly delayed fruit senescence by reducing ethylene production and maintained fruit quality. It is suggested that the effects of BRs on reducing decay caused by P. expansum may be associated with induction of disease resistance in fruit and delay of senescence.

Physiological disorders easily occur in Laiyang pear (Pyrus bretschneideri cv. Laiyang) fruit after harvest and result in quality deterioration and short postharvest life. In this paper, we mainly investigated the effects of 1-methylcyclopropene (1-MCP) treatment and controlled atmosphere (CA) with 2% O2 plus 2% CO2 on quality of Laiyang pear and storage time. The results indicated that 1-MCP treatment and CA were effective in maintaining quality and prolonging storage time of Laiyang pear fruit, because 1-MCP and CA could significantly delay fruit senescence via limiting ethylene production, reducing fruit respiration rate, regulating anti-oxidant enzymes and membrane permeability. We consider that the major action modes of 1-MCP and CA, that can maintain harvested quality of Laiyang pear fruit, may be greatly contributed to inhibiting ethylene biosynthesis and regulating anti-oxidant pathways.Highlights► 1-MCP treatment and CA storage can maintain quality and prolong storage life of Laiyang pear. ► 1-MCP treatment and CA storage inhibit fruit respiration rate and ethylene production. ► 1-MCP treatment and CA storage inhibit membrane lipid peroxidation to maintain membrane integrity. ► 1-MCP treatment and CA storage enhance anti-oxidant capacity to scavenge ROS.

•Environmental factors show effect on patulin production in Penicillium expansum.•Carbon and nitrogen sources can regulate patulin biosynthesis.•Acidic conditions are more favorable for patulin production than alkaline conditions.•Patulin biosynthesis is regulated at transcriptional level by environmental factors.Patulin, a potent mycotoxin which can cause serious health concerns, is mainly produced in foods by Penicillium expansum. Environmental factors play important roles in regulating biosynthesis of mycotoxins; however, information about the effects of environmental factors on patulin production and the involved mechanisms in P. expansum is limited. Here, we investigated the effects of different carbon (C) and nitrogen (N) sources, and ambient pH on patulin production in three P. expansum strains T01, M1 and Pe21, and the expression profile of 15 genes involved in patulin biosynthetic pathway. It was found that C and N sources and pH had great influence on patulin production in P. expansum. In general, patulin production of all three P. expansum strains showed similar trends under different C and N sources and pH conditions, though there were some differences in the optimal conditions among these strains. Glucose-containing sugars, complex N sources, and acidic conditions were favorable conditions for patulin production. The results of RT-qPCR showed that the relative expressions of most of the patulin genes were up-regulated under patulin-permissive conditions, indicating that patulin biosynthesis was mainly regulated at transcriptional level by these environmental factors. These findings will provide useful information to better understand the regulation mechanisms of patulin biosynthesis, and be helpful in developing effective means for controlling patulin contamination.

In this paper, we investigated the effect of exogenous methyl jasmonate (MeJA) on gray mould rot caused by Botrytis cinerea in tomato fruit and its mechanism related to reactive oxygen species (ROS) metabolism. The results indicated that MeJA at a concentration of 10 mM effectively inhibited lesion diameter of gray mould rot in tomato fruit. Resistant response of MeJA-treated tomato fruit to B. cinerea was attributed to an accumulation of H2O2, concomitant with enhanced Cu–Zn superoxide dismutase (Cu–Zn SOD) gene expression and decreased catalase (CAT) transcript level during the early stage of storage. However, MeJA treatment stimulated CAT and ascorbate peroxidase (APX) gene expression, enhanced ascorbate (ASC) and glutathione (GSH) content, being beneficial for scavenging excess ROS and alleviating oxidative damage of proteins. These results indicated that mechanisms involved in the induction of the fruit resistance to B. cinerea might be associated with elicitation of antioxidative reaction and prevention of protein carbonylation in fruit. In addition, MeJA negatively affected plasma membrane integrity of B. cinerea spores and showed direct antimicrobial activity in vitro, suggesting MeJA has direct fungitoxic property against the pathogen.Highlights► We investigated the effect of methyl jasmonate (MeJA) on oxidative defense to Botrytis cinerea in tomato fruit. ► MeJA treatment can increase antioxidant capacity of fruit to scavenge excess ROS. ► We used new biochemical markers in tomato fruit to confirm that MeJA alleviated pathogen-induced oxidative damage.

In order to elucidate whether fruit maturity stage influence the induced resistance of exogenous elicitors in tomato and the involved mechanisms, we investigated the defense responses of tomato fruits against Botrytis cinerea, ethylene production and internal quality following treatments of fruit with salicylic acid (SA) or ethephon (ET) at mature green (MG) and breaker (BR). SA significantly suppressed decay and disease incidence in tomato fruits at both MG and BR stages, along with higher expression level of PR1 gene after 2 days of treatment. All fruits treated by SA had lower contents of ethylene and lycopene. The ET-treated fruit at both maturity stages showed lower disease incidence and higher level of PR2 and PR3 expression compared with the control fruit. ET treatment significantly enhanced ethylene and lycopene contents, and accelerated fruit ripening. Our results suggest that SA and ET induced disease resistance in fruits by mediating the expression of different pathogenesis-related genes and have different effects on fruit ripening, which in turn influences the disease resistance of tomato fruits.Highlights► SA reduced the decay caused by Botrytis cinerea in fruits at both MG and BR stage. ► ET-treated fruit at both maturity stages showed lower disease incidence. ► Maturity had little effect on fruit defense responses induced by exogenous elicitors. ► SA and ET induced resistance in fruit by mediating the expression of different PRs. ► SA and ET differently affected fruit ripening, which in turn altered fruit resistance.