Characterization and Action Mechanism of Phytotoxins

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Plant Toxins".

Deadline for manuscript submissions: closed (25 August 2023) | Viewed by 9543

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Guest Editor
1. Department of Chemical Sciences, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy
2. Institute of Sciences of Food Production, National Research Council, Via Amendola 122/O, 70125 Bari, Italy
Interests: Fungi; Bacterial; plant; metabolites; chemistry; spectroscopy; stereochemistry; biological activity; structure-activity relationships
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Dear Colleagues,

Phytotoxins are microbial secondary metabolites that play an important role in the development of plant disease symptoms. Plant pathogenesis is a very complex process beginning with plant–pathogen interaction and subsequently the production of microorganisms by enzymes and secondary metabolites to overcome plant resistant and those produced by plant to activate defense mechanisms. Phytotoxins belong to several classes of natural metabolites such as terpenes, pyrones, furanones, cyclohexene oxides, aromatic compounds, non-natural amino acids, etc. Plant economic diseases have been studied for many years for their heavy impact on agrarian, forest and ornamental heritage and consequently the severe losses in quality, quantity and safety of agrarian crops, nurseries and wood industries. The purification and characterization of these toxic metabolites today have become much simpler and more efficient with respect to the huge development of new chromatographic and spectroscopic methods. Very important is the determination of their absolute configuration strictly close the biological activity. Thus, pure metabolites could have an important practical application in agriculture, such as biopesticides, as an alternative to chemicals, which reduces environmental pollution and risks for human and animal health. Phytotoxins could also be an important tool to develope specific and sensitive diagnostic methods for plant disease and can be used to obtain crop varieties that are resistant to diseases. Some of them, particularly those with original carbon skeletons, could also have application in medicine with respect to combating severe human diseases such as malaria, yellow and dengue fevers and cancer, which have caused the death of millions of people for years, overcoming the increasing resistance to common pharmaceuticals that are antibiotic and anticancer. Phytotoxins could be used to carry out structure–activity relationship studies to modulate their activity and specificity and to prepare probed derivatives suitable for study on their mode of action. The results of these studies could be very surprising as it was already discovered that some studied phytotoxins possess plant receptors that are very similar to the group of proteins that recognize the same compounds in animals.

Thus, this Special Issue of Toxins will report articles with respect to phytotoxin characterization and the results of studies on their mode of action.

Prof. Dr. Antonio Evidente
Guest Editor

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Keywords

  • plant
  • phytotoxins
  • chemical and biological characterization
  • sar studies
  • mode action

Published Papers (4 papers)

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Research

29 pages, 8874 KiB  
Article
Effects of Phytotoxic Nonenolides, Stagonolide A and Herbarumin I, on Physiological and Biochemical Processes in Leaves and Roots of Sensitive Plants
by Elena V. Tyutereva, Anna A. Dalinova, Kirill N. Demchenko, Valeriya A. Dmitrieva, Vsevolod R. Dubovik, Yuriy V. Lukinskiy, Galina V. Mitina, Olga V. Voitsekhovskaja and Alexander Berestetskiy
Toxins 2023, 15(4), 234; https://doi.org/10.3390/toxins15040234 - 23 Mar 2023
Cited by 2 | Viewed by 1975
Abstract
Phytotoxic macrolides attract attention as prototypes of new herbicides. However, their mechanisms of action (MOA) on plants have not yet been elucidated. This study addresses the effects of two ten-membered lactones, stagonolide A (STA) and herbarumin I (HBI) produced by the fungus Stagonospora [...] Read more.
Phytotoxic macrolides attract attention as prototypes of new herbicides. However, their mechanisms of action (MOA) on plants have not yet been elucidated. This study addresses the effects of two ten-membered lactones, stagonolide A (STA) and herbarumin I (HBI) produced by the fungus Stagonospora cirsii, on Cirsium arvense, Arabidopsis thaliana and Allium cepa. Bioassay of STA and HBI on punctured leaf discs of C. arvense and A. thaliana was conducted at a concentration of 2 mg/mL to evaluate phenotypic responses, the content of pigments, electrolyte leakage from leaf discs, the level of reactive oxygen species, Hill reaction rate, and the relative rise in chlorophyll a fluorescence. The toxin treatments resulted in necrotic and bleached leaf lesions in the dark and in the light, respectively. In the light, HBI treatment caused the drop of carotenoids content in leaves on both plants. The electrolyte leakage caused by HBI was light-dependent, in contrast with that caused by STA. Both compounds induced light-independent peroxide generation in leaf cells but did not affect photosynthesis 6 h after treatment. STA (10 µg/mL) caused strong disorders in root cells of A. thaliana leading to the complete dissipation of the mitochondrial membrane potential one hour post treatment, as well as DNA fragmentation and disappearance of acidic vesicles in the division zone after 8 h; the effects of HBI (50 µg/mL) were much milder. Furthermore, STA was found to inhibit mitosis but did not affect the cytoskeleton in cells of root tips of A. cepa and C. arvense, respectively. Finally, STA was supposed to inhibit the intracellular vesicular traffic from the endoplasmic reticulum to the Golgi apparatus, thus interfering with mitosis. HBI is likely to have another main MOA, probably inhibiting the biosynthesis of carotenoids. Full article
(This article belongs to the Special Issue Characterization and Action Mechanism of Phytotoxins)
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10 pages, 1079 KiB  
Article
In Vitro Effects of Fungal Phytotoxins on Cancer Cell Viability: First Insight into Structure Activity Relationship of a Potent Metabolite of Cochliobolus australiensis Radicinin
by Veronique Mathieu, Stefano Superchi, Marco Masi, Patrizia Scafato, Alexander Kornienko and Antonio Evidente
Toxins 2022, 14(8), 517; https://doi.org/10.3390/toxins14080517 - 29 Jul 2022
Cited by 4 | Viewed by 1658
Abstract
Natural compounds have always represented an important source for new drugs. Although fungi represent one such viable source, to date, no fungal metabolite has been marketed as an anticancer drug. Based on our work with phytotoxins as potential chemical scaffolds and our recent [...] Read more.
Natural compounds have always represented an important source for new drugs. Although fungi represent one such viable source, to date, no fungal metabolite has been marketed as an anticancer drug. Based on our work with phytotoxins as potential chemical scaffolds and our recent findings involving three phytopathogenic fungi, i.e., Cochliobolus australiensis, Kalmusia variispora and Hymenoscyphus fraxineus, herein, we evaluate the in vitro anti-cancer activity of the metabolites of these fungi by MTT assays on three cancer cell models harboring various resistance levels to chemotherapeutic drugs. Radicinin, a phytotoxic dihydropyranopyran-4,5-dione produced by Cochliobolus australiensis, with great potential for the biocontrol of the invasive weed buffelgrass (Cenchrus ciliaris), showed significant anticancer activity in the micromolar range. Furthermore, a SAR study was carried out using radicinin, some natural analogues and hemisynthetic derivatives prepared by synthetic methods developed as part of work aimed at the potential application of these molecules as bioherbicides. This investigation opens new avenues for the design and synthesis of novel radicinin analogues as potential anticancer agents. Full article
(This article belongs to the Special Issue Characterization and Action Mechanism of Phytotoxins)
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16 pages, 3051 KiB  
Article
Cyclopaldic Acid, the Main Phytotoxic Metabolite of Diplodia cupressi, Induces Programmed Cell Death and Autophagy in Arabidopsis thaliana
by Simone Samperna, Marco Masi, Maurizio Vurro, Antonio Evidente and Mauro Marra
Toxins 2022, 14(7), 474; https://doi.org/10.3390/toxins14070474 - 11 Jul 2022
Cited by 8 | Viewed by 2087
Abstract
Cyclopaldic acid is one of the main phytotoxic metabolites produced by fungal pathogens of the genus Seiridium, causal agents, among others, of the canker disease of plants of the Cupressaceae family. Previous studies showed that the metabolite can partially reproduce the symptoms [...] Read more.
Cyclopaldic acid is one of the main phytotoxic metabolites produced by fungal pathogens of the genus Seiridium, causal agents, among others, of the canker disease of plants of the Cupressaceae family. Previous studies showed that the metabolite can partially reproduce the symptoms of the infection and that it is toxic to different plant species, thereby proving to be a non-specific phytotoxin. Despite the remarkable biological effects of the compound, which revealed also insecticidal, fungicidal and herbicidal properties, information about its mode of action is still lacking. In this study, we investigated the effects of cyclopaldic acid in Arabidopsis thaliana plants and protoplasts, in order to get information about subcellular targets and mechanism of action. Results of biochemical assays showed that cyclopaldic acid induced leaf chlorosis, ion leakage, membrane-lipid peroxidation, hydrogen peroxide production, inhibited root proton extrusion in vivo and plasma membrane H+-ATPase activity in vitro. qRT-PCR experiments demonstrated that the toxin elicited the transcription of key regulators of the immune response to necrotrophic fungi, of hormone biosynthesis, as well as of genes involved in senescence and programmed cell death. Confocal microscopy analysis of protoplasts allowed to address the question of subcellular targets of the toxin. Cyclopaldic acid targeted the plasma membrane H+-ATPase, inducing depolarization of the transmembrane potential, mitochondria, disrupting the mitochondrial network and eliciting overproduction of reactive oxygen species, and vacuole, determining tonoplast disgregation and induction of vacuole-mediated programmed cell death and autophagy. Full article
(This article belongs to the Special Issue Characterization and Action Mechanism of Phytotoxins)
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18 pages, 3038 KiB  
Article
Physicochemical, Pharmacokinetic and Cytotoxicity of the Compounds Isolated from an Endophyte Fusarium oxysporum: In Vitro and In Silico Approaches
by Nazia Hoque, Farhana Afroz, Farjana Khatun, Satyajit Roy Rony, Choudhury Mahmood Hasan, Md. Sohel Rana and Md. Hossain Sohrab
Toxins 2022, 14(3), 159; https://doi.org/10.3390/toxins14030159 - 23 Feb 2022
Cited by 3 | Viewed by 2622
Abstract
The present study was intended to characterize the secondary metabolites of the endophyte Fusarium oxysporum isolated from the plant Aglaonema hookerianum Schott. And to investigate the cytotoxic and other pharmacological properties of the isolated compounds as part of the drug discovery and development [...] Read more.
The present study was intended to characterize the secondary metabolites of the endophyte Fusarium oxysporum isolated from the plant Aglaonema hookerianum Schott. And to investigate the cytotoxic and other pharmacological properties of the isolated compounds as part of the drug discovery and development process. Different chromatographic techniques were adopted to isolate the bioactive compounds that were identified by spectroscopic techniques. The cytotoxic properties of the compounds were assessed in the Vero cell line via the trypan blue method. Moreover, physicochemical, pharmacokinetic, bioactivity and toxicity profiles of the compounds were also investigated through in silico approaches. After careful spectral analysis, the isolated compounds were identified as 3β,5α-dihydroxy-ergosta-7,22-dien-6-one (1), 3β,5α,9α-trihydroxy-ergosta-7,22-dien-6-one (2), p-hydroxybenzaldehyde (3), 3-(R)-7-butyl-6,8-dihydroxy-3-pent-11-enylisochroman-1-one (4) and beauvericin (5). An in vitro study in the Vero cell line revealed that the presence of the compounds reduced the number of cells, as well as the percentage of viable cells, in most cases. An in silico cytotoxic analysis revealed that compounds 1, 2 and 5 might be explored as cytotoxic agents. Moreover, compounds 3 and 4 were found to be highly mutagenic. The present study suggested that further thorough investigations are necessary to use these molecules as leads for the cytotoxic drug development process. Full article
(This article belongs to the Special Issue Characterization and Action Mechanism of Phytotoxins)
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