A new strategy for browning regulation: Flos Sophorae Immaturus extract and thermal treatment modulates nitric oxide and reactive oxygen species network in fresh-cut potatoes.

Browning discoloration is a critical issue that negatively affects the quality of fresh-cut products and their industrial growth. Although many individual anti-browning technologies have been adopted, very few reports on the combination use of natural product extracts and physical methods exist. This study investigated the use of Flos Sophorae Immaturus extract in conjunction with thermal treatment and discovered that the combination effectively retarded browning in fresh-cut potatoes. Accordingly, the activities of polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase, as well as phenol accumulation, were effectively regulated. Meanwhile, this combination treatment also allowed for the modulation of nitric oxide synthase, superoxide dismutase, and catalase activities, while also regulating the concentrations of nitric oxide, superoxide anion, and hydrogen peroxide. Furthermore, the duplex treatment also regulated the antioxidant capacity and malondialdehyde concentrations. In addition, 39 phytoactive compounds, including protocatechuic acid, quercetin, (-)-alpha-pinene, and matrine, were identified in the extract, which may function as the anti-browning composition. These findings suggest that the combination technology modulated the dynamic equilibrium of production and clearance of nitric oxide and reactive oxygen species, thereby reducing browning deterioration. This is, to our knowledge, the first report of the combined application of Flos Sophorae Immaturus and thermal treatment, which may offer a novel option for fresh-cut preservation. PRACTICAL APPLICATION: The feasibility of integrating a novel highly efficient, safe, environmentally friendly, and easy-to-operate anti-browning alternative, with the ability to integrate into the existing processing line was investigated. The color of sliced potato chips was significantly improved (73.4%) by dipping them in a 0.01% Flos Sophorae Immaturus solution for 5 min and then in 55°C water for 2 min. In this regard, superior browning alleviation may depend on the regulation of the browning reaction and the NO-ROS network. This method has a promising future for making fresh-cut products more appealing to consumers and may provide guidance for fresh-cut producers and related industries.

Herbal smoke fumigation for controlling Penicillium crustosum in fresh walnuts.

Fresh walnuts have a high water content and are susceptible to decay, and controlling fungal contamination during storage is vital to walnut marketing. In this research, the dominant pathogenic fungus of fresh walnuts was first identified as Penicillium crustosum by morphological and molecular methods. The antifungal effect of herbal smoke fumigation was tested in vitro and in vivo, including Myristica fragrans Houtt., Aucklandia lappa Decne., Eugenia caryophyllata Thunb., Atractylodes lancea (Thunb.) DC., Shiraia bambusicola Henn., Artemisia argyi Lévl. et Vant. The results demonstrated that smoke from all six herbs successfully inhibited P. crustosum growth, and A. argyi smoke produced the best antifungal effect, which contained higher contents of phenol (17.1%), eugenol (13.7%), hexacosane, tetracontane, heneicosane, linolenic acid and other antimicrobial components by gas chromatography-mass spectrometry. Interestingly, optical transmittance data were found to correlate with antifungal capacity, revealing that a formed physical barrier combined with the above antimicrobial compositions, to participate in mold controlling together. Finally, fumigation with A. argyi smoke was tested in a real storage situation at proper dose, which not only dramatically controlled fungal contamination (>70%), but also maintained better odor and taste without oxidative rancidity or other adverse effects. This is the first report in which herbal smoke fumigation was adopted to preserve fresh walnut, providing a new way to reduce mold contamination and maintain quality of fresh walnuts in a natural and safe manner. More research on the application of herbal smoke fumigation to agricultural products in post-harvest storage is needed to explore the conditions and products for which it can be used successfully.

N-Acetylglucosamine Promotes Tomato Plant Growth by Shaping the Community Structure and Metabolism of the Rhizosphere Microbiome.

Communication between plants and microorganisms is vital because it influences their growth, development, defense, propagation, and metabolism in achieving maximal fitness. N-acetylglucosamine (N-GlcNAc), the building block of bacterial and fungal cell walls, was first reported to promote tomato plant growth via stimulation of microorganisms typically known to dominate the tomato root rhizosphere, such as members of Proteobacteria and Actinobacteria. Using KEGG pathway analysis of the rhizosphere microbial operational taxonomic units, the streptomycin biosynthesis pathway was enriched in the presence of N-GlcNAc. The biosynthesis of 3-hydroxy-2-butanone (acetoin) and 2,3-butanediol, two foremost types of plant growth promotion-related volatile organic compounds, were activated in both Bacillus subtilis and Streptomyces thermocarboxydus strains when they were cocultured with N-GlcNAc. In addition, the application of N-GlcNAc increased indole-3-acetic acid production in a dose-dependent manner in strains of Bacillus cereus, Proteus mirabilis, Pseudomonas putida, and S. thermocarboxydus that were isolated from an N-GlcNAc-treated tomato rhizosphere. Overall, this study found that N-GlcNAc could function as microbial signaling molecules to shape the community structure and metabolism of the rhizosphere microbiome, thereby regulating plant growth and development and preventing plant disease through complementary plant-microbe interactions. IMPORTANCE While the benefits of using plant growth-promoting rhizobacteria (PGPRs) to enhance crop production have been recognized and studied extensively under laboratory conditions, the success of their application in the field varies immensely. More fundamentally explicit processes of positive, plant-PGPRs interactions are needed. The utilization of organic amendments, such as chitin and its derivatives, is one of the most economical and practical options for improving soil and substrate quality as well as plant growth and resilience. In this study, we observed that the chitin monomer N-GlcNAc, a key microbial signaling molecule produced through interactions between chitin, soil microbes, and the plants, positively shaped the community structure and metabolism of the rhizosphere microbiome of tomatoes. Our findings also provide a new direction for enhancing the benefits and stability of PGPRs in the field.

Polyphenol-Polysaccharide Complex: Preparation, Characterization, and Potential Utilization in Food and Health.

Polysaccharides and polyphenols coexist in many plant-based food products. Polyphenol-polysaccharide interactions may affect the physicochemical, functional, and physiological properties, such as digestibility, bioavailability, and stability, of plant-based foods. In this review, the interactions (physically or covalently linked) between the selected polysaccharides and polyphenols are summarized. The preparation and structural characterization of the polyphenol-polysaccharide conjugates, their structural-interaction relationships, and the effects of the interactions on functional and physiological properties of the polyphenol and polysaccharide molecules are reviewed. Moreover, potential applications of polyphenol-polysaccharide conjugates are discussed. This review aids in a comprehensive understanding of the synthetic strategy, beneficial bioactivity, and potential application of polyphenol-polysaccharide complexes.

Fungus Polygalacturonase-Generated Oligogalacturonide Restrains Fruit Softening in Ripening Tomato.

Fruit softening exacerbates mechanical damage incurred during shipping and handling and the increase in pathogen susceptibility. Here, oligogalacturonides (OGs) produced by fungal polygalacturonase (PG) delayed fruit softening in tomato and maintained fruit firmness at 8.37 ± 0.45 N at 13 d of storage, which was consistent with the fruit firmness level of 5 d in the control groups. From RNA sequencing data in line production of phytohormones, we confirmed ethylene and jasmonic acid signals, the MAPK signaling cascade, and calmodulin involved in the OG-mediated firmness response of whole fruit. SlPG2, SlPL3, and SlPL5 were the major contributing factors for fruit softening, and their expression decreased continuously upon OG application. Suppression of the expression of ethylene response factors using a virus-induced gene-silencing strategy revealed that SlERF6 was negatively involved in OG-restrained fruit softening. Taken together, these results indicated that fungal PG-generated OGs have potential application value in controlling tomato fruit softening.

Novel alternative for controlling enzymatic browning: Catalase and its application in fresh-cut potatoes.

Surface browning is a vital phenomenon that adversely reduces the quality of fresh-cut potatoes. Although many anti-browning methods have been explored, it is unclear whether exogenous catalase (CAT) treatment influences the enzymatic browning. Our results showed that 0.05% CAT immersion for 5 min alleviated browning during cold storage (4°C, 8 days), which was accompanied by a higher lightness and lower redness; additionally, lower H2 O2 and O2 ·- contents were found. The activities of CAT, ascorbate peroxidase, and glutathione peroxidase and the scavenging efficiency of 2,2-diphenyl-1-picrylhydrazyl were also increased. Moreover, CAT treatment inhibited the activities of polyphenol oxidase, peroxidase, and phenylalanine ammonia lyase and reduced phenol accumulation. Treatment with 0.1% hydrogen peroxide (H2 O2 ) achieved the opposite results. This is the first report of CAT application reducing fresh-cut potato browning, providing a safe treatment alternative for enzymatic discoloration and preliminarily revealing the underlying mechanism with insight into antioxidant regulation. PRACTICAL APPLICATION: This research is helpful for fresh-cut potato producers because a novel, safe, easy-to-carry out anti-browning solution was proposed. Dipping in 0.05% catalase solution for 5 min revealed color improvement in the quality of fresh-cut potato slices. The mechanism may rely on enhancing antioxidant ability (ascorbate peroxidase, and glutathione peroxidase, and 2,2-diphenyl-1-picrylhydrazyl scavenging), reducing reactive oxygen species (H2 O2 , O2 ·-, malondialdehyde) and controlling enzymatic browning reaction factors (polyphenol oxidase, peroxidase, and phenylalanine ammonia lyase, and phenol accumulation). This method shows promise for better meeting the requirements and demands of consumers for fresh quality products.

Novel browning alleviation technology for fresh-cut products: Preservation effect of the combination of Sonchus oleraceus L. extract and ultrasound in fresh-cut potatoes.

Enzymatic browning is considered a critical factor that adversely decreases the quality of fresh-cut products. Although many individual physical or chemical methods have been explored to control browning, there are few approaches combining these technologies. In the present study, Sonchus oleraceus L. extract (SOLE) and ultrasound treatment efficiently controlled the activities of polyphenol oxidase, peroxidase, phenylalanine ammonia-lyase, lipoxygenase, soluble quinones, and intermediate and advanced products, and a lower malondialdehyde content and higher antioxidant capacity were observed in fresh-cut potato slices. More than 50 phenolics and flavonoids were identified in SOLE by liquid chromatography-tandem mass spectrometry. In conclusion, the combined SOLE and ultrasound treatment could serve as a promising method for attenuating enzymatic browning.

Oligogalacturonide-accelerated healing of mechanical wounding in tomato fruit requires calcium-dependent systemic acquired resistance.

Mechanical wounding causes significant economic losses of fresh produce due to accelerated senescence and spoilage as well as loss of nutritional value. Here, pre-application of oligogalacturonides (OGs) enzymatically hydrolyzed from apple pectin effectively reduced the healing times of mechanical wounds from>24 h in mock groups to 12 h, and the Botrytis cinerea infection rate was reduced from 37.5% to 12.5%. OGs accordingly increased callose deposition; SlPR1, SlPAL and SlHCT gene expression; and phenylalanine ammonia-lyase (PAL) activity around the wounds. Inhibition of Ca2+ signaling using the inhibitor Ruthenium Red markedly inhibited OG accelerated healing of mechanical wounding on fruit. SlPG2, SlEXP1, and SlCEL2 mRNAs accumulation was reduced in OG-elicited tomato fruit compared to water-treated fruit with subsequent retardation of the fruit softening during ripening. These results indicated that apple pectin OGs accelerate wound healing and inhibit fruit softening by activating calcium signaling in tomato fruits during postharvest storage.

Dextran as an elicitor of phenylpropanoid and flavonoid biosynthesis in tomato fruit against gray mold infection.

Alpha-1,3-glucan is often synthesized on the surface of pathogenic filamentous fungi cell walls to block pathogen-associated molecular patterns (PAMPs) generation by host plant enzymes and the subsequent immune system response of the plant. Here, Botrytis cinerea susceptibility was assessed in tomato fruit to determine whether the fruit could recognize this camouflage and mount an immune response to it. The results showed that local mechanical wounds treated with dextran and laminarin, except amylopectin, could locally and then systemically activate disease resistance against B. cinerea infection in tomato fruit. Dextran treatment effectively elicited fruit callose deposition and phenylpropanoid and flavonoid biosynthesis to a greater extent than α-glucanase activity relative to the mock group surface wounds. Enzymatic hydrolysis of this polysaccharide provided some help in improving host disease resistance. Taken together, these results demonstrate that tomato fruit can perceive α-1,3-glucan as a kind of PAMPs but have limited ability to degrade it.

Biocontrol activity of volatile organic compounds from Streptomyces alboflavus TD-1 against Aspergillus flavus growth and aflatoxin production.

Aspergillus flavus is a saprophytic fungus that contaminates crops with carcinogenic aflatoxin. In the present work, the antifungal effects of volatile organic compounds (VOCs) from Streptomyces alboflavus TD-1 against A. flavus were investigated. VOCs from 8-day-old wheat bran culture of S. alboflavus TD-1 displayed strong inhibitory effects against mycelial growth, sporulation, and conidial germination of A. flavus. Severely misshapen conidia and hyphae of A. flavus were observed by scanning electron microscopy after exposure to VOCs for 6 and 12 h, respectively. Rhodamine 123 staining of mitochondria indicated that mitochondria may be a legitimate antifungal target of the VOCs from S. alboflavus TD-1. Furthermore, the VOCs effectively inhibited aflatoxin B1 production by downregulating genes involved in aflatoxin biosynthesis. Dimethyl trisulfide and benzenamine may play important roles in the suppression of A. flavus growth and production of aflatoxin. The results indicate that VOCs from S. alboflavus TD-1 have tremendous potential to be developed as a useful bio-pesticide for controlling A. flavus.

Depression of Fungal Polygalacturonase Activity in Solanum lycopersicum Contributes to Antagonistic Yeast-Mediated Fruit Immunity to Botrytis.

The acquisition of susceptibility to necrotrophy over the course of ripening is one of the critical factors limiting shelf life. In this study, phytopathology and molecular biology were employed to explore the roles of pectinase in fruit susceptibility and ripening. Solanum lycopersicum fruit softened dramatically from entirely green to 50% red, which was accompanied by a continuously high expressed SlPG2 gene. The necrotrophic fungus Botrytis cinerea further activated the expression of SlPGs and SlPMEs to accelerate cell wall disassembly, while most of the polygalacturonase inhibitor proteins encoding genes expression were postponed in ripe fruit following the pathogen attack. Pectin induced the antagonistic yeast to secrete pectinolytic enzymes to increase fruit resistance against gray mold. The activities of pathogenic pectinase of B. cinerea were correspondingly depressed in the pectin-inducible yeast enzyme elicited ripe fruit. These data suggest that pectinase is a molecular target for regulation of disease resistance during fruit ripening.

Transcriptomic Insights into Benzenamine Effects on the Development, Aflatoxin Biosynthesis, and Virulence of Aspergillus flavus.

Aspergillus flavus is a soilborne pathogenic fungus that poses a serious public health threat due to it contamination of food with carcinogenic aflatoxins. Our previous studies have demonstrated that benzenamine displayed strong inhibitory effects on the mycelial growth of A. flavus. In this study, we systematically investigated the inhibitory effects of benzenamine on the development, aflatoxin biosynthesis, and virulence in A. flavus, as well as the underlying mechanism. The results indicated that benzenamine exhibited great capacity to combat A. flavus at a concentration of 100 µL/L, leading to significantly decreased aflatoxin accumulation and colonization capacity in maize. The transcriptional profile revealed that 3589 genes show altered mRNA levels in the A. flavus after treatment with benzenamine, including 1890 down-regulated and 1699 up-regulated genes. Most of the differentially expressed genes participated in the biosynthesis and metabolism of amino acid, purine metabolism, and protein processing in endoplasmic reticulum. Additionally, the results brought us to a suggestion that benzenamine affects the development, aflatoxin biosynthesis, and pathogenicity of A. flavus via down-regulating related genes by depressing the expression of the global regulatory factor leaA. Overall, this study indicates that benzenamine have tremendous potential to act as a fumigant against pathogenic A. flavus. Furthermore, this work offers valuable information regarding the underlying antifungal mechanism of benzenamine against A. flavus at the level of transcription, and these potential targets may be conducive in developing new strategies for preventing aflatoxin contamination.

Cryptococcus laurentii controls gray mold of cherry tomato fruit via modulation of ethylene-associated immune responses.

This research aimed to investigate the roles of phytohormone ethylene in cherry tomato fruit immune response against gray mold caused by Botrytis cinerea. Pretreatment with antagonistic yeast Cryptococcus laurentii resulted in a significantly decreased disease incidence of B. cinerea infection, and accompanied by a burst of ethylene production in the whole fruit. Blocking the ethylene perception by adding 1-MCP (5 µL L-1 or greater) remarkably weaken the protection ability of fruit itself and suppressed the C. laurentii-stimulated host immune response. 5 µL L-1 1-MCP prefumigation decreased the expression of ethylene biosynthesis and perception related genes SlACO1, SlACS2, SlERF1, SlPti5 and SlMPK3, and ethylene production in C. laurentii treated fruit. Consequently, the expressions of SlCHI9, SlGlub, SlPAL3, SlPR1 and SlPR5 up-regulated by the yeast were all impaired to different degrees by the 1-MCP prefumigation. These findings demonstrate that ethylene contributes to fruit immunity and C. laurentii-mediated immune responses of cherry tomato.

Immunomodulatory effect of a formula developed from American ginseng and Chinese jujube extracts in mice.

BACKGROUND: American ginseng (Panax quinquefolius L.) and Chinese jujube (Zizyphus jujuba Mill.) are commonly used in traditional Chinese medicine to enhance immune function. OBJECTIVE: The present study aimed to develop one Chinese prescription, Shenzao Cha (SZC), consisting of American ginseng and Chinese jujube, and systematically investigate its immunomodulation in healthy ICR mice. METHODS: Normal ICR mice received intragastric administration of SZC (1.3, 2.6, and 5.2 g raw material/kg body weight) once daily for four weeks, while a control group received the same amount of sterile water. RESULTS: SZC significantly increased the spleen and thymus indices and T-lymphocyte proliferation, while the T-lymphocyte proliferation in the 5.2 g/kg group was 1.4-fold higher than that in the control. Further, 1.3 g/kg SZC could markedly improve hemolytic activity by 25.2%, and 2.6 g/kg SZC increased the NK cell activity by 78.6% relative to the control. In addition, the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase), that participated in modulating oxidative stress, were significantly increased in the liver, spleen, thymus, and serum, while the contents of malondialdehyde were dramatically decreased. CONCLUSIONS: SZC exhibited potent immunomodulatory effects on innate and adaptive immunity in healthy ICR mice, as well as potential antioxidant activity for prevention of oxidative stress, which was suggested to partly contribute to the immune enhancement.

Rhamnolipids induce oxidative stress responses in cherry tomato fruit to Alternaria alternata.

BACKGROUND: Rhamnolipids showed an antimicrobial activity applicable to a variety of pathogenic microorganisms, but mechanisms were mostly focused on their direct inhibitory effect. RESULTS: This study showed that disease incidence obviously decreased when cherry tomatoes were treated with rhamnolipids, whether before or after Alternaria alternata inoculation. The activities of antioxidant enzymes, including superoxide dismutase and catalase, were increased in rhamnolipid-pretreated cherry tomato inoculated with A. alternata within 12 h, while contents of reactive oxygen species decreased. Moreover, resistant response of cherry tomato treated with rhamnolipids and A. alternata was also attributed to activity stimulation of ascorbate peroxidase and glutathione reductase, accompanied with an increase in reduced glutathione, which is beneficial for scavenging excessive H2 O2 . CONCLUSION: Results indicated that rhamnolipids could effectively reduce fungal disease of harvested cherry tomato by inducing fruit resistance and mechanisms involved in elicitation of antioxidative reactions such as the ability to scavenge excess reactive oxygen species. © 2015 Society of Chemical Industry.

Transcript profiling analysis of Rhodosporidium paludigenum-mediated signalling pathways and defense responses in mandarin orange.

To investigate the basis of inducible resistance response in postharvest mandarin orange, cDNA microarray and high-performance liquid chromatography were performed to study transcriptional and metabolic changes in Rhodosporidium paludigenum strain treated fruit. The microarray data mining revealed that R. paludigenum activated transcription of genes important for plant hormones, signalling transduction, stress and defensive responses in orange peel tissue. Moreover, up-regulation of phenylalanine and tyrosine metabolism, phenylpropanoids biosynthesis, and alkaloid biosynthesis I, were observed at the transcription level. Conversely, large amounts of genes involved in starch metabolism, oligosaccharide and glycoside metabolism were markedly repressed by R. paludigenum treatment. Activation of phenylpropanoids biosynthesis pathway was correlated with the increasing production of phenolic acids and their subsequent metabolite lignin, indicating antifungal metabolites indeed contributed to biocontrol yeast enhanced fruit protection. Our findings provide an important basis for understanding the mechanisms of resistance induction in mandarin orange, as well as for reducing postharvest losses.

Quaternary chitosan oligomers enhance resistance and biocontrol efficacy of Rhodosporidium paludigenum to green mold in satsuma orange.

This study investigated the capacity of chitosan oligomers (COS), applied before harvest singly or in combination with antagonists, in controlling postharvest green mold caused by Penicillium digitatum in satsuma orange. Oranges treated with COS or Rhodosporidium paludigenum were observed having a delay in onset and progression of disease symptoms relative to wounded controls. Preharvest application of COS at different concentrations achieved similar biocontrol efficiency rates in green mold control after 4 days storage. However, the combination of pre-COS (1%, w/v) and R. paludigenum showed a more effective decay control than any other treatments. COS (1%, w/v) alone did not negatively affect R. paludigenum growth in wounds, but severely inhibited P. digitatum spore germination than lower dose treatments in vitro. The expression levels of the defense-related genes chitinase and phenylalanine ammonia lyase increased with decreased disease symptoms. Moreover, this phenomenon was more prominent in the integrated treatments than in the individual ones.

Bioactive flavones and biflavones from Selaginella moellendorffii Hieron.

Three new flavones named 5-carboxymethyl-4',7-dihydroxyflavone (1), its ethyl ester (2) and butyl ester (3) were isolated from the herb Selaginella moellendorffii Hieron., together with ten known compounds. Their structures were elucidated on the basis of spectroscopic and chemical analysis. Selected compounds were evaluated for their anti-HBV and cytotoxic activity. Among them, compounds 2 and 3 displayed inhibitory activity in vitro on hepatitis B virus (HBV) surface antigen (HBsAg) secretion of the Hep G2.2.15 cell line with IC(50) values of 0.17 mg/ml and 0.46 mg/ml, and on HBV e antigen (HBeAg) secretion with IC(50) values of 0.42 mg/ml and 0.42 mg/ml, respectively. Compounds 7, 8, 10 and 12 exhibited selective cytotoxicity against the three human cancer cell lines tested.