MOLECULAR AND GENETIC APPROACHES TO SUPPRESSING FUNGAL PATHOGENS AND MYCOTOXIN CONTAMINATION
Location: Plant Mycotoxin Research
Title: Chemosensitization of aflatoxigenic fungi to antimycin A and strobilurin using salicylaldehyde, a volatile natural compound targeting cellular antioxidation system
Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 5, 2010
Publication Date: August 29, 2010
Citation: Kim, J.H., Campbell, B.C., Mahoney, N.E., Chan, K.L., Molyneux, R.J. 2010. Chemosensitization of aflatoxigenic fungi to antimycin A and strobilurin using salicylaldehyde, a volatile natural compound targeting cellular antioxidation system. Mycopathologia. 171(4):291-298.
Interpretive Summary: Aflatoxin is a carcinogenic compound produced by certain fungi. As such, contamination of food products by aflatoxin is a serious food-safety issue. Sometimes, the fungi that produce aflatoxin show high activity while the food product (such as almonds) is being stockpiled in preparation for processing. PMR scientists have discovered a volatile, safe, natural compound, salicylaldehyde, which shows promise as a fumigant to suppress fungal growth and aflatoxin production. This compound functions by stressing the ability of the fungus to detoxify chemicals that buildup in the fungus under heat and sunlight. Moreover, this compound augments the activity of two commercial antifungal agents such that the amount of this agent needed to control the fungus is significantly reduced. The results show that salicyladehyde could serve as a safe fumigant to control aflatoxin contamination while harvested crop product is awaiting further processing.
Salicylaldehyde (SA), a volatile natural compound, exhibited potent antifungal and antiaflatoxigenic activities to Aspergillus flavus and A. parasiticus. Exposure to volatilized SA, inhibited growth of A. parasiticus from 10% - 75% at 9.5 - 16.0 mM, with complete inhibition at 19.0 mM. Similar trends were observed with A. flavus. Production of aflatoxin B1 and B2 (AFB1, AFB2) for A. flavus and AFB1, AFB2, AFG1, AFG2 for A. parasiticus, in the SA-treated (9.5 mM) fungi was reduced by ~13% to 45% compared with the untreated control. Using the model yeast Saccharomyces cerevisiae, we identified the fungal antioxidation system as the molecular target of SA, where cytosolic superoxide dismutase (SOD), mitochondrial SOD and glutathione reductase mutants showed increased sensitivity to this compound. Also sensitive was the gene deletion mutant 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 resulted in complete growth inhibition of Aspergillus at much lower doses of either agent, alone. SA is a potent antifungal and antiaflatoxigenic volatile that may have some practical application as a fumigant.