Chemosensitization of Aflatoxigenic Fungi to Antimycin A and Strobilurin Using Salicylaldehyde,a Volatile Natural Compound Targeting Cellular Antioxidation System |
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Authors: | Jong H Kim Bruce C Campbell Noreen Mahoney Kathleen L Chan Russell J Molyneux |
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Institution: | (1) Plant Mycotoxin Research Unit, Western Regional Research Center, USDA-ARS, 800 Buchanan Street, Albany, CA 94710, USA; |
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Abstract: | Various species of fungi in the genus Aspergillus are the most common causative agents of invasive aspergillosis and/or producers of hepato-carcinogenic mycotoxins. Salicylaldehyde
(SA), a volatile natural compound, exhibited potent antifungal and anti-mycotoxigenic activities to A. flavus and A. parasiticus. By exposure to the volatilized SA, the growth of A. parasiticus was inhibited up to 10–75% at 9.5 mM ≤ SA ≤ 16.0 mM, while complete growth inhibition was achieved at 19.0 mM ≤ SA. Similar
trends were also observed with A. flavus. The aflatoxin production, i.e., aflatoxin B1 and B2 (AFB1, AFB2) for A. flavus and AFB1, AFB2, AFG1, and AFG2 for A. parasiticus, in the SA-treated (9.5 mM) fungi was reduced by ~13–45% compared with the untreated control. Using gene deletion mutants
of the model yeast Saccharomyces cerevisiae, we identified the fungal antioxidation system as the molecular target of SA, where sod1Δ cytosolic superoxide dismutase (SOD)], sod2Δ (mitochondrial SOD), and glr1Δ (glutathione reductase) mutants showed increased sensitivity to this compound. Also sensitive was the gene deletion mutant,
vph2Δ, for the vacuolar ATPase assembly protein, suggesting vacuolar detoxification plays an important role for fungal tolerance
to SA. In chemosensitization experiments, co-application of SA with either antimycin A or strobilurin (inhibitors of mitochondrial
respiration) resulted in complete growth inhibition of Aspergillus at much lower dose treatment of either agent, alone. Therefore, SA can enhance antifungal activity of commercial antifungal
agents required to achieve effective control. SA is a potent antifungal and anti-aflatoxigenic volatile that may have some
practical application as a fumigant. |
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