Sodium pheophorbide a controls cherry tomato gray mold (Botrytis cinerea) by destroying fungal cell structure and enhancing disease resistance-related enzyme activities in fruit

Caffeic acid improves biocontrol effect of Pantoea jilinensis D25 against tomato gray mold

BACKGROUND

Gray mold in tomato caused by Botrytis cinerea is a destructive disease, which can be treated using biocontrol agents. Pretreatment of biocontrol strains with oxidative-stress-ameliorating compounds can enhance their tolerance to oxidative microenvironment in infected fruit wounds. In this study, we aimed to determine the effect of caffeic acid (CA) on the biocontrol efficacy of Pantoea jilinensis D25 in gray mold in cherry tomato.

RESULTS

D25 strain pretreated with CA exhibited enhanced oxidative stress response in cherry tomato wounds. CA-treated D25 cells recovered from cherry tomato wounds had lower ROS level and cellular oxidative damage than D25 cells not treated with CA. The antioxidation-related genes (CAT and GPX) were upregulated and colonization ability of D25 strain was improved in cherry tomato wounds after CA application. Furthermore, the biocontrol effects of CA-treated D25 strain were improved. CA pretreatment to D25 strain could significantly improve the expression of defense-related genes (SlMYC-2, SlLoxD, SlEIN2, and SlEIN3) and activity of defense-related enzymes in cherry tomato wounds.

CONCLUSION

Application of CA to D25 strain could improve its ability to combat antioxidant stress and biocontrol efficacy against postharvest tomato gray mold. © 2024 Society of Chemical Industry.

Antifungal activity of paeonol against Botrytis cinerea by disrupting the cell membrane and the application on cherry tomato preservation

Botrytis cinerea may cause gray mold in fruits and vegetables. Paeonol, an active component of traditional Chinese medicine, could suppress various microbial growth. However, reports on its effect on B. cinerea have not yet been documented. In this paper, we demonstrated that paeonol completely inhibited B. cinerea growth at 250 mg/L, corroborated by the observation of irregular morphological alterations in B. cinerea exposed to paeonol. Notably, the investigation of the operating mechanism revealed that paeonol induced cell death by disrupting the cell membrane, potentially mediated by the interaction between paeonol and ergosterol from the membrane. Further studies indicated that paeonol decreased ergosterol content and the expression of certain genes involved in ergosterol biosynthesis was significantly downregulated. In addition, paeonol treatment reduced the gray mold of cherry tomatoes. Meanwhile, compared to the control treatment, paeonol treatment could reduce weight loss and maintain higher contents of total soluble solid (TSS) and ascorbic acid, leading to a higher quality of the stored cherry tomato. Together, the data indicate that paeonol was effective as an alternative agent targeting disrupting the cell membrane to control gray mold and prolong the shelf life of cherry tomatoes, suggesting that paeonol could be used as a natural antifungal compound during postharvest storage.

A novel synthesized Vanillin-Based Deep Eutectic Agent (V-DEA) mitigates postharvest fungal decay and improve shelf life and quality of cherry tomatoes

Fusarium oxysporum and Botrytis cinerea are the main pathogens that cause fruit decay and reduce the postharvest shelf life of cherry tomatoes. Boosting the potency of natural products requires implementing structural modification to combat postharvest pathogens. Herein, we developed a novel Vanillin-Deep Eutectic Agent (V-DEA) from natural compounds and evaluated its effectiveness against tomato fruit rot pathogens. The results demonstrated that V-DEA suppressed mycelium growth and spore germination of F. oxysporum and B. cinerea by enhancing cell membrane permeability, increasing lipid peroxidation, and inhibiting enzyme activities. Importantly, using 8-mM V-DEA successfully prevented postharvest decay in cherry tomatoes, while 4-mM significantly extended their shelf life by reducing weight loss and shriveling, and enhancing key fruit qualities such as total soluble solids, ascorbic acid, tartaric acid, and lycopene. In conclusion, V-DEA exhibits dual properties as a potent pathogen inhibitor and antioxidant activity, thus prolonging the shelf life of cherry tomatoes.

Cucumber PGIP2 is involved in resistance to gray mold disease

Polygalacturonase inhibitor protein (PGIP) restricts fungal growth and colonization and functions in plant immunity. Gray mold in cucumber is a common fungal disease caused by Botrytis cinerea, and is widespread and difficult to control in cucumber (Cucumis sativus L.) production. In this study, Cucumis sativus polygalacturonase-inhibiting protein 2 (CsPGIP2) was found to be upregulated in response to gray mold in cucumber. CsPGIP2 was detected in the endoplasmic reticulum, cell membrane, and cell wall after transient transformation of protoplasts and tobacco. A possible interaction between Botrytis cinerea polygalacturonase 3 (BcPG3) and CsPGIP2 was supported by protein interaction prediction and BiFC analysis. Transgenic Arabidopsis plants expressing CsPGIP2 were constructed and exhibited smaller areas of gray mold infection compared to wild type (WT) plants after simultaneous inoculation. Evans blue dye (EBD) confirmed greater damage for WT plants, with more intense dyeing than for the transgenic Arabidopsis. Interestingly, compared to WT, transgenic Arabidopsis exhibited higher superoxide dismutase (AtSOD1) expression, antioxidant enzyme activities, lignin content, net photosynthetic rate (Pn), and photochemical activity. Our results suggest that CsPGIP2 stimulates a variety of plant defense mechanisms to enhance transgenic Arabidopsis resistance against gray mold disease.

The photoactivated antifungal activity and possible mode of action of sodium pheophorbide a on Diaporthe mahothocarpus causing leaf spot blight in Camellia oleifera

Introduction

Sodium pheophorbide a (SPA) is a natural plant-derived photosensitizer, with high photoactivated antifungal activity against some phytopathogenic fungi. However, its fungicidal effect on Diaporthe mahothocarpus, a novel pathogen that causes Camellia oleifera leaf spot blight, is unclear.

Methods

In the present study, we explored its inhibitory effects on spore germination and mycelial growth of D. mahothocarpus. Then we determined its effects on the cell membrane, mycelial morphology, redox homeostasis, and cell death through bioassay. Finally, RNA-seq was used further to elucidate its mode of action at the transcriptional level.

Results

We found that SPA effectively inhibited the growth of D. mahothocarpus, with half-maximal effective concentrations to inhibit mycelial growth and spore germination of 1.059 and 2.287 mg/mL, respectively. After 1.0 mg/mL SPA treatment, the conductivity and malondialdehyde content of D. mahothocarpus were significantly increased. Scanning electron microscopy and transmission electron microscopy indicated that SPA significantly affected the morphology and ultrastructure of D. mahothocarpus hyphae, revealing that SPA can destroy the mycelial morphology and cell structure, especially the cell membrane of D. mahothocarpus. Furthermore, transcriptome analysis revealed that SPA significantly suppressed the expression of genes involved in morphology, cell membrane permeability, and oxidative stress. Then, we also found that SPA significantly promoted the accumulation of reactive oxygen species (ROS) in of D. mahothocarpus, while it decreased the content of reduced glutathione, inhibited the enzyme activities of superoxide dismutase and catalase, and exacerbated DNA damage. Annexin V-FITC/PI staining also confirmed that 1.0 mg/mL SPA could significantly induce apoptosis and necrosis.

Discussion

Generally, SPA can induce ROS-mediated oxidative stress and cell death, thus destroying the cell membrane and hyphal morphology, and ultimately inhibiting mycelial growth, which indicates that SPA has multiple modes of action, providing a scientific basis for the use of SPA as an alternative plant-derived photoactivated fungicide against C. oleifera leaf spot blight.

Bioassay-guided isolation of three new alkaloids from Suillus bovinus and preliminary mechanism against ginseng root rot

In order to control the occurrence of ginseng root rot caused by Fusarium solani (Mart.) Sacc., the antifungal compounds of the mushroom Suillus bovinus were investigated. And three new alkaloids (1-3), named bovinalkaloid A-C, along with one known analog (4), were isolated and identified by bioassay-guided isolation and spectroscopic analyses. Compound 1 strongly inhibited the mycelial growth and spore germination of F. solani with minimum inhibitory concentration of 2.08 mM. Increases in electrical conductivity, nucleic acid, and protein contents, and decreases in lipid content showed that the membrane permeability and integrity were damaged by compound 1. Compound 1 also increased the contents of malondialdehyde and hydrogen peroxide and the activities of antioxidant enzymes, indicating that lipid peroxidation had taken place in F. solani. Compound 1 may serve as a natural alternative to synthetic fungicides for the control of ginseng root rot.

Lignite-steel slag constructed wetland with multi-functionality and effluent reuse

Constructed wetlands (CWs) are widely used to treat wastewater, while innovative studies are needed to support resource conservation, enhance multi-functionality, and improve the effectiveness of effluent usage. This study assessed the potential of CW's multiple functions by combining low-rank coal (lignite) and industrial waste (steel slag) in different configurations as CW substrates. The results of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and metagenomic sequencing showed that the experimental treatment with lignite and steel slag mixtures had the highest multi-functionality, including efficient nutrient removal and carbon sequestration, as well as hydroponic crop production. Lignite and steel slag were mixed to form lignite-steel slag particle clusters, where Ca2+ dissolved on the surface of steel slag was combined with PO43- in wastewater to form Ca3(PO4)2 precipitation for phosphorus removal. A biofilm grew on the surface of lignite in this cluster, and OH- released from steel slag promoted lignite to release fulvic acid, which provided a carbon source for heterotrophic microorganisms and promoted denitrification. Moreover, fulvic acid enhanced carbon sequestration in CWs by increasing the biomass of Phragmites australis. The effluent from lignite-steel slag CW increased cherry tomato yield and quality while saving N and P applications. These results provide new ideas for the "green" and economic development of CW technology.

TMT-Based Proteomic Analysis Reveals the Molecular Mechanisms of Sodium Pheophorbide A against Black Spot Needle Blight Caused by Pestalotiopsis neglecta in Pinus sylvestris var. mongolica

Black spot needle blight is a minor disease in Mongolian Scots pine (Pinus sylvestris var. mongolica) caused by Pestalotiopsis neglecta, but it can cause economic losses in severe cases. Sodium pheophorbide a (SPA), an intermediate product of the chlorophyll metabolism pathway, is a compound with photoactivated antifungal activity, which has been previously shown to inhibit the growth of P. neglecta. In this study, SPA significantly reduced the incidence and disease index and enhanced the chlorophyll content and antioxidant enzyme activities of P. sylvestris var. mongolica. To further study the molecular mechanism of the inhibition, we conducted a comparative proteomic analysis of P. neglecta mycelia with and without SPA treatment. The cellular proteins were obtained from P. neglecta mycelial samples and subjected to a tandem mass tag (TMT)-labelling LC-MS/MS analysis. Based on the results of de novo transcriptome assembly, 613 differentially expressed proteins (DEPs) (p < 0.05) were identified, of which 360 were upregulated and 253 downregulated. The 527 annotated DEPs were classified into 50 functional groups according to Gene Ontology and linked to 256 different pathways using the Kyoto Encyclopedia of Genes and Genomes database as a reference. A joint analysis of the transcriptome and proteomics results showed that the top three pathways were Amino acid metabolism, Carbohydrate metabolism, and Lipid metabolism. These results provide new viewpoints into the molecular mechanism of the inhibition of P. neglecta by SPA at the protein level and a theoretical basis for evaluating SPA as an antifungal agent to protect forests.

Ursolic acid, the main component of blueberry cuticular wax, inhibits Botrytis cinerea growth by damaging cell membrane integrity

Cuticular wax has been reported to play an essential role in resisting pathogens in various fruits. This study investigated the antifungal ability of the components in blueberry cuticular wax. We showed that the cuticular wax of blueberry inhibited the growth of Botrytis cinerea and ursolic acid (UA) was the key antifungal compound. UA inhibited B. cinerea growth in vitro and in vivo. Furthermore, UA increased extracellular conductivity and cellular leakage in B. cinerea, deformed the mycelial morphology, and destroyed cell ultrastructure. We also demonstrated that UA stimulated the accumulation of reactive oxygen species (ROS) and inactivated ROS scavenging enzymes. These results indicate that UA may exert antifungal effects against B. cinerea by disrupting cell membrane integrity. Thus, UA has significant potential as an agent for the control of gray mold in blueberry.

Inhibitory effect and mechanism of action of juniper essential oil on gray mold in cherry tomatoes

Juniper essential oil (JEO), which is mostly known as an immune system booster and effective detoxifier, has substantial antimicrobial activity. A comparison of the inhibitory effects of three plant essential oils from juniper (Juniperus rigida), cedarwood (Juniperus virginiana), and cypress (Crupressus sempervirens) on four plant pathogenic fungi indicated that JEO was the most effective at inhibiting the growth of gray mold (Botrytis cinerea). Additional studies were subsequently conducted to explore the in vivo and in vitro antifungal activity and possible mechanism of JEO against B. cinerea. The results show that JEO inhibited the germination of spores and mycelial growth of B. cinerea in a concentration-dependent manner and exhibited strong inhibition when its concentration exceeded 10 μL/mL. JEO also significantly inhibited the incidence of disease and diameters of gray mold lesions on cherry tomato fruit (Solanum lycopersicum). After 12 h of treatment with JEO, the extracellular conductivity, and the contents of soluble protein, malondialdehyde, and hydrogen peroxide were 3.1, 1.2, 7.2, and 4.7 folds higher than those of the control group, respectively (P < 0.05), which indicated that JEO can damage membranes. Scanning electron microscopy observations revealed that JEO affected the morphology of mycelia, causing them to shrivel, twist and distort. Furthermore, JEO significantly improved the activities of the antioxidant-related enzymes superoxide dismutase and catalase but reduced the pathogenicity-related enzymes polygalacturonase (PG), pectin lyase and endoglucanase of B. cinerea (P < 0.05). In particular, PG was reduced by 93% after treatment with JEO for 12 h. Moreover, the 18 constituents of JEO were identified by gas chromatography/mass spectrometry (GC-MS) analysis, mainly limonene (15.17%), γ-terpinene (8.3%), β-myrcene (4.56%), terpinen-4-ol (24.26%), linalool (8.73%), α-terpineol (1.03%), o-cymene (8.35%) and other substances with antimicrobial activity. Therefore, JEO can be an effective alternative to prevent and control gray mold on cherry tomato fruit.

Ultrasound-mediated molecular self-assemble of thymol with 2-hydroxypropyl-β-cyclodextrin for fruit preservation

In this study, the inclusion complex (IC) of thymol with 2-hydroxypropyl-β-cyclodextrin (HPβCD) was fast synthetized by ultrasonic technology and its antifungal activities were evaluated. The thymol/HPβCD-IC was characterized by UV-vis absorption spectroscopy, fluorescence emission spectroscopy, powder X-ray diffraction, FT-IR, 1H-NMR, TGA and DSC. The phase solubility studies proved that the aqueous solubility of thymol was significantly improved by forming the inclusion complex with HPβCD, and the thermal stability analysis showed that thymol/HPβCD-IC had a better thermal stability than pure thymol. The in vitro antifungal activities of thymol/HPβCD-IC against Botrytis cinerea, Penicillium digitatum and Alternaria alternata were significantly improved compared with pure thymol. Furthermore, the gray mold rot of tomatoes was evidently inhibited by thymol/HPβCD-IC treatment in vivo study. Therefore, the complexation with HPβCD assisted by ultrasound is a promising approach to solubilize and stabilize thymol for application as an antifungal agent in fruit preservation.

Inhibitory effects and mechanisms of vanillin on gray mold and black rot of cherry tomatoes

Vanillin is a natural antimicrobial agent; however, there are few reports on its antifungal effect on postharvest pathogenic fungi. This study aimed to investigate the in vivo and in vitro antifungal activities of vanillin against gray mold (caused by B. cinerea) and black rot (caused by A. alternata) of cherry tomato fruit and to explain its possible mechanism of action. Vanillin strongly inhibits Botrytis cinerea and Alternaria alternata mycelial growth, spore germination, and germ tube elongation in a concentration-dependent manner (P<0.05). In vivo experiments showed that 4000 mg L^-1 vanillin treatment inhibited cherry tomato gray mold and black rot occurrence. Besides, intercellular electrolytes, soluble proteins, and soluble sugars leakage indicated that 50 or 100 mg L^-1 vanillin treatment increased Botrytis cinerea and Alternaria alternata membrane permeability. The increase of malondialdehyde and hydrogen peroxide contents confirmed that 50 or 100 mg L^-1 vanillin treatment damages the pathogen membranes. Importantly, vanillin treatment inhibited the pathogenicity-related enzyme activities of the two pathogens to reduce their infection ability, among them PL enzyme activity in A. alternata was most inhibited, reducing by 94.7 % at 6 h treated with 100 mg L^-1 vanillin. The hyphae morphology of the two pathogens changed, the mycelia were severely damaged, and the hyphae surface was deformed, shrunk, or even broken after 100 mg L^-1 vanillin treatment. In summary, vanillin had a substantial inhibitory effect on postharvest gray mold and black rot in cherry tomato fruit. Therefore, vanillin can be an effective alternative to prevent and control cherry tomato postharvest diseases.

The α-Subunit of the Chloroplast ATP Synthase of Tomato Reinforces Resistance to Gray Mold and Broad-Spectrum Resistance in Transgenic Tobacco

Chloroplast ATP synthase (cpATPase) is responsible for ATP production during photosynthesis. Our previous studies showed that the cpATPase CF1 α subunit (AtpA) is a key protein involved in Clonostachys rosea-induced resistance to the fungus Botrytis cinerea in tomato. Here, we show that expression of the tomato atpA gene was upregulated by B. cinerea and Clonostachys rosea. The tomato atpA gene was then isolated, and transgenic tobacco lines were obtained. Compared with untransformed plants, atpA-overexpressing tobacco showed increased resistance to B. cinerea, characterized by reduced disease incidence, defense-associated hypersensitive response-like reactions, balanced reactive oxygen species, alleviated damage to the chloroplast ultrastructure of leaf cells, elevated levels of ATP content and cpATPase activity, and enhanced expression of genes related to carbon metabolism, photosynthesis, and defense. Incremental Ca2+ efflux and steady H+ efflux were observed in transgenic tobacco after inoculation with B. cinerea. In addition, overexpression of atpA conferred enhanced tolerance to salinity and resistance to the fungus Cladosporium fulvum. Thus, AtpA is a key regulator that links signaling to cellular redox homeostasis, ATP biosynthesis, and gene expression of resistance traits to modulate immunity to pathogen infection and provides broad-spectrum resistance in plants in the process.