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Shcherbakova L, Mikityuk O, Arslanova L, Stakheev A, Erokhin D, Zavriev S, Dzhavakhiya V. Studying the Ability of Thymol to Improve Fungicidal Effects of Tebuconazole and Difenoconazole Against Some Plant Pathogenic Fungi in Seed or Foliar Treatments. Front Microbiol 2021; 12:629429. [PMID: 33717020 PMCID: PMC7947622 DOI: 10.3389/fmicb.2021.629429] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 02/03/2021] [Indexed: 12/16/2022] Open
Abstract
Thymol, a secondary plant metabolite possessing antifungal and chemosensitizing activities, disrupts cell wall or membrane integrity and interferes with ergosterol biosynthesis. Thymol also functions as a redox-active compound inducing generation of reactive oxygen species and lipid peroxidation in fungal cells. Previously, we showed thymol significantly enhanced the in vitro growth inhibitory effect of difenoconazole against Bipolaris sorokiniana and Parastagonospora nodorum. More recently, we demonstrated a possibility to use thymol to overcome the resistance of a P. nodorum strain able to grow on difenoconazole-containing media. However, potential for thymol to serve as a chemosensitizing agent in seed or plant treatments, to provide an effective suppression of the above-mentioned plant pathogens by triazole fungicides applied in lowered dosages, had yet to be tested. In the work presented here, we showed combined treatments of naturally infected barley seeds with thymol and difenoconazole (Dividend® 030 FS) synergistically exacerbated the protective effect against common root rot agent, B. sorokiniana, and other fungi (Fusarium spp. and Alternaria spp.). Similarly, co-applied treatment of wheat seeds, artificially inoculated with Fusarium culmorum, resulted in equivalent reduction of disease incidence on barley seedlings as application of Dividend®, alone, at a ten-fold higher dosage. In foliar treatments of wheat seedlings, thymol combined with Folicur® 250 EC (a.i. tebuconazole) enhanced sensitivity of P. nodorum, a glume/leaf blotch pathogen, to the fungicide and provided a significant mitigation of disease severity on treated seedlings, compared to controls, without increasing Folicur® dosages. Folicur® co-applied with thymol was also significantly more effective against a strain of P. nodorum tolerant to Folicur® alone. No additional deoxynivalenol or zearalenone production was found when a toxigenic F. culmorum was cultured in a nutrient medium containing thymol at a concentration used for chemosensitization of root rot agents. Accordingly, F. culmorum exposure to thymol at the sensitizing concentration did not up-regulate key genes associated with the biosynthesis of trichothecene or polyketide mycotoxins in this pathogen. Further studies using field trials are necessary to determine if thymol-triazole co-applications result in sensitization of seed- and foliar-associated plant pathogenic fungi, and if thymol affects production of fusarial toxins under field conditions.
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Affiliation(s)
- Larisa Shcherbakova
- Laboratory of Physiological Plant Pathology, All-Russian Research Institute of Phytopathology, Moscow, Russia
| | - Oleg Mikityuk
- Laboratory of Physiological Plant Pathology, All-Russian Research Institute of Phytopathology, Moscow, Russia
| | - Lenara Arslanova
- Department of Molecular Biology, All-Russian Research Institute of Phytopathology, Moscow, Russia
| | - Alexander Stakheev
- Laboratory of Molecular Diagnostics, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Denis Erokhin
- Department of Molecular Biology, All-Russian Research Institute of Phytopathology, Moscow, Russia
| | - Sergey Zavriev
- Laboratory of Molecular Diagnostics, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Vitaly Dzhavakhiya
- Department of Molecular Biology, All-Russian Research Institute of Phytopathology, Moscow, Russia
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A Human IRE1 Inhibitor Blocks the Unfolded Protein Response in the Pathogenic Fungus Aspergillus fumigatus and Suggests Noncanonical Functions within the Pathway. mSphere 2020; 5:5/5/e00879-20. [PMID: 33087521 PMCID: PMC7580959 DOI: 10.1128/msphere.00879-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus. The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response. The unfolded protein response (UPR) is a signaling network that maintains homeostasis of the endoplasmic reticulum (ER). In the human-pathogenic fungus Aspergillus fumigatus, the UPR is initiated by activation of an endoribonuclease (RNase) domain in the ER transmembrane stress sensor IreA, which splices the downstream mRNA hacAu into its active form, hacAi, encoding the master transcriptional regulator of the pathway. Small-molecule inhibitors against IRE1, the human ortholog of IreA, have been developed for anticancer therapy, but their effects on the fungal UPR are unexplored. Here, we demonstrate that the IRE1 RNase inhibitor 4μ8C prevented A. fumigatus from increasing the levels of hacAi mRNA, thereby blocking induction of downstream UPR target gene expression. Treatment with 4μ8C had minimal effects on growth in minimal medium but severely impaired growth on a collagen substrate that requires high levels of hydrolytic enzyme secretion, mirroring the phenotype of other fungal UPR mutants. 4μ8C also increased sensitivity to carvacrol, a natural compound that disrupts ER integrity in fungi, and hygromycin B, which correlated with reduced expression of glycosylation-related genes. Interestingly, treatment with 4μ8C was unable to induce all of the phenotypes attributed to the loss of the canonical UPR in a ΔhacA mutant but showed remarkable similarity to the phenotype of an RNase-deficient IreA mutant that is also unable to generate the hacAi mRNA. These results establish proof of principle that pharmacological inhibition of the canonical UPR pathway is feasible in A. fumigatus and support a noncanonical role for the hacAu mRNA in ER stress response. IMPORTANCE The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus. The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response.
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Li Q, Zhu X, Xie Y, Ren S. 2‐Hydroxy‐4‐methoxybenzaldehyde inhibits the growth of
Aspergillus flavus
via damaging cell wall, cell membrane, manipulating respiration thus creating a promising antifungal effect on corn kernels. Int J Food Sci Technol 2020. [DOI: 10.1111/ijfs.14617] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Qian Li
- School of Food Science and Technology Henan University of Technology Zhengzhou 450001 HenanChina
- Henan Key Laboratory of cereal and Oil Food Safety Inspection and Control Zhengzhou 450001 HenanChina
| | - Xiaoman Zhu
- School of Food Science and Technology Henan University of Technology Zhengzhou 450001 HenanChina
- Henan Key Laboratory of cereal and Oil Food Safety Inspection and Control Zhengzhou 450001 HenanChina
| | - Yanli Xie
- School of Food Science and Technology Henan University of Technology Zhengzhou 450001 HenanChina
- Henan Key Laboratory of cereal and Oil Food Safety Inspection and Control Zhengzhou 450001 HenanChina
| | - Shilin Ren
- School of Food Science and Technology Henan University of Technology Zhengzhou 450001 HenanChina
- Henan Key Laboratory of cereal and Oil Food Safety Inspection and Control Zhengzhou 450001 HenanChina
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Kim JH, Chan KL, Mahoney N, Cheng LW, Tautges N, Scow K. Rapid elimination of foodborne and environmental fungal contaminants by benzo analogs. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2020; 100:2800-2806. [PMID: 31975411 DOI: 10.1002/jsfa.10288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 12/31/2019] [Accepted: 01/08/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND Contamination of food or the environment by fungi, especially those resistant to conventional fungicides or drugs, represents a hazard to human health. The objective of this study is to identify safe, natural antifungal agents that can remove fungal pathogens or contaminants rapidly from food and / or environmental sources. RESULTS Fifteen antifungal compounds (nine benzo derivatives as candidates; six conventional fungicides as references) were investigated. Three benzo analogs, namely octyl gallate (OG), trans-cinnamaldehyde (CA), and 2-hydroxy-5-methoxybenzaldehyde (2H5M), at 1 g L-1 (3.54 mmol), 1 mL L-1 (7.21 mmol), 1 mL L-1 (5.39 mmol), respectively, achieved ≥99.9% fungal death after 0.5, 2.5 or 24 h of treatments, respectively, in in vitro phosphate-buffered saline (PBS) bioassay. However, when OG, CA, and 2H5M were examined in commercial food matrices, organic apple, or grape juices, only CA maintained a similar level of antifungal activity, compared with a PBS bioassay. trans-Cinnamaldehyde showed higher antifungal activity at pH 3.5, equivalent to that of commercial fruit juices, than at pH 5.6. In soil sample tests, the application of 1 mL L-1 (7.21 mmol) CA to conventional maize / tomato soil samples (pH 6.8) for 2.5 h resulted in ≥99.9% fungal death, indicating CA could also eliminate fungal contaminants in soil. While the conventional fungicide thiabendazole exerted antifungal activity comparable to CA, thiabendazole enhanced the production of carcinogenic aflatoxins by Aspergillus flavus, an undesirable side effect. CONCLUSION trans-Cinnamaldehyde could be developed as a potent antifungal agent in food processing or soil sanitation by reducing the time / cost necessary for fungal removal. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.
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Affiliation(s)
- Jong H Kim
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, Albany, CA, USA
| | - Kathleen L Chan
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, Albany, CA, USA
| | - Noreen Mahoney
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, Albany, CA, USA
| | - Luisa W Cheng
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, Albany, CA, USA
| | - Nicole Tautges
- Department of Land, Air and Water Resources, University of California, Davis, CA, USA
| | - Kate Scow
- Department of Land, Air and Water Resources, University of California, Davis, CA, USA
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Kim JH, Chan KL, Cheng LW, Tell LA, Byrne BA, Clothier K, Land KM. High Efficiency Drug Repurposing Design for New Antifungal Agents. Methods Protoc 2019; 2:mps2020031. [PMID: 31164611 PMCID: PMC6632159 DOI: 10.3390/mps2020031] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 04/09/2019] [Accepted: 04/12/2019] [Indexed: 01/19/2023] Open
Abstract
Current antifungal interventions have often limited efficiency in treating fungal pathogens, particularly those resistant to commercial drugs or fungicides. Antifungal drug repurposing is an alternative intervention strategy, whereby new utility of various marketed, non-antifungal drugs could be repositioned as novel antifungal agents. In this study, we investigated “chemosensitization” as a method to improve the efficiency of antifungal drug repurposing, wherein combined application of a second compound (viz., chemosensitizer) with a conventional, non-antifungal drug could greatly enhance the antifungal activity of the co-applied drug. Redox-active natural compounds or structural derivatives, such as thymol (2-isopropyl-5-methylphenol), 4-isopropyl-3-methylphenol, or 3,5-dimethoxybenzaldehyde, could serve as potent chemosensitizers to enhance antifungal activity of the repurposed drug bithionol. Of note, inclusion of fungal mutants, such as antioxidant mutants, could also facilitate drug repurposing efficiency, which is reflected in the enhancement of antifungal efficacy of bithionol. Bithionol overcame antifungal (viz., fludioxonil) tolerance of the antioxidant mutants of the human/animal pathogen Aspergillus fumigatus. Altogether, our strategy can lead to the development of a high efficiency drug repurposing design, which enhances the susceptibility of pathogens to drugs, reduces time and costs for new antifungal development, and abates drug or fungicide resistance.
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Affiliation(s)
- Jong H Kim
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, 800 Buchanan St., Albany, CA 94710, USA.
| | - Kathleen L Chan
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, 800 Buchanan St., Albany, CA 94710, USA.
| | - Luisa W Cheng
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, USDA-ARS, 800 Buchanan St., Albany, CA 94710, USA.
| | - Lisa A Tell
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Barbara A Byrne
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Kristin Clothier
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA.
- California Animal Health and Food Safety Laboratory, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Kirkwood M Land
- Department of Biological Sciences, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA.
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Ngo HX, Garneau-Tsodikova S, Green KD. A complex game of hide and seek: the search for new antifungals. MEDCHEMCOMM 2016; 7:1285-1306. [PMID: 27766140 PMCID: PMC5067021 DOI: 10.1039/c6md00222f] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Fungal infections directly affect millions of people each year. In addition to the invasive fungal infections of humans, the plants and animals that comprise our primary food source are also susceptible to diseases caused by these eukaryotic microbes. The need for antifungals, not only for our medical needs, but also for use in agriculture and livestock causes a high demand for novel antimycotics. Herein, we provide an overview of the most commonly used antifungals in medicine and agriculture. We also present a summary of the recent progress (from 2010-2016) in the discovery/development of new agents against fungal strains of medical/agricultural relevance, as well as information related to their biological activity, their mode(s) of action, and their mechanism(s) of resistance.
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Affiliation(s)
- Huy X. Ngo
- University of Kentucky, Department of Pharmaceutical Sciences, 789 South Limestone Street, Lexington, KY, USA. Fax: 859-257-7585; Tel: 859-218-1686
| | - Sylvie Garneau-Tsodikova
- University of Kentucky, Department of Pharmaceutical Sciences, 789 South Limestone Street, Lexington, KY, USA. Fax: 859-257-7585; Tel: 859-218-1686
| | - Keith D. Green
- University of Kentucky, Department of Pharmaceutical Sciences, 789 South Limestone Street, Lexington, KY, USA. Fax: 859-257-7585; Tel: 859-218-1686
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