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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR AND GENETIC APPROACHES TO SUPPRESSING FUNGAL PATHOGENS AND MYCOTOXIN CONTAMINATION

Location: Foodborne Toxin Detection and Prevention

2008 Annual Report


1a.Objectives (from AD-416)
Objectives of the research .
1)Release a promising insect resistant, premium quality almond variety, and evaluate other advanced breeding selections..
2)Characterize almond seed coat tannins at the genetic and biochemical levels and examine associaion of specific antioxidants with seed coat ink staining..
3)Identify and integrate multiple resistances into regionally adapted, high commercial quality breeding selections. Reduce mycotoxin contamination of agricultural commodities focusing on tree nuts (almonds, pistachios and walnuts) by identifying natural constituents or biocompetitive organisms that inhibit growth of fungi and aflatoxin production. Identify target genes in fungi that trigger mycotoxin biosynthesis focusing on stress response pathways.


1b.Approach (from AD-416)
Identify the natural constituents responsible for resistance of certain varieties of tree nuts to growth of aflatoxigenic strains of aspergillus. Isolate and identify novel metabolites in sclerotia of Aspergillus and develop analytical methods for such compounds in order to assess exposure levels of tree nut orchards to the fungus. Identify genes involved in triggering mycotoxin biosynthesis using high-throughput bioassays. Assays involve use of deletion mutants, gene knockouts and complementation analysis. Discover natural compounds that disrupt functionality of gene targets identified. Develop biosensors for detecting toxic fungi in pre- and post harvest environments.


3.Progress Report
Aflatoxin is a highly carcinogenic compound produced by certain fungi that can infect a wide variety of edible agricultural products, Aflatoxin contamination is a major food safety issue and is strictly regulated, resulting in it also being a significant international trade issue. USDA scientists in the Plant Mycotoxin Research Unit, Albany, CA, provided two major breakthroughs in research on preventing aflatoxin. MU scientists discovered natural products that prevent aflatoxin biosynthesis. These compounds are antioxidants. MU molecular biologists were able to show that these anti-aflatoxigenic compounds mainly affect genes involved in the oxidative stress response mechanisms of fungi. In collaboration with scientists in the Food and Feed Safety Research Unit, New Orleans, LA, MU scientists were able to identify the genes that suppress aflatoxin biosynthesis. The USDA scientists were able to show that certain genes that are involved in producing more enzymes (peroxiredoxins) that degrade certain compounds (mainly fats) in fungi that change as a result of exposure to oxygen. As a result, the aflatoxin biosynthetic pathway is completely “turned off”. This finding has already led to the breeding of a new variety of almond, "Sweetheart", by collaborators from the University of California, Davis, that has higher levels of antioxidants in the kernel seedcoat. This work supports NP 108 Component 2.1.4.

The second major breakthrough was discovery of safe natural compounds that enhance antifungal activity of commercial fungicides and antifungal drugs. Fungal infection of crop plants poses a major problem to agricultural productivity, quality of agricultural products and food safety resulting from toxins that certain fungi produce. Additionally, there is a certain fungi that are significant human pathogens, whose infection can lead to serious debilitation or death. USDA scientists in the Plant Mycotoxin Research Unit, Albany, CA have identified a number of safe, natural products that can significantly enhance the effectiveness of commercial fungicides, such as strobilurin and fludioxonil. These natural compounds are used to weaken the ability of the fungi to build their cell walls or to respire normally. Once these fungi are weakened by this “chemo-sensitization” the commercial products are anywhere from 100 to 1000 fold more effective. In collaboration with scientists at the Institute of Hygiene and Tropical Medicine, Lisbon, Portugal, chemosensitization was effective against a number of human pathogenic fungi by increasing effectivness of antifungal drugs, such as itraconazole or fluconazole, against strains that had become resistant to these drugs. PMR scientists won the "Thomas J. Walsh Award for Clinical Mycology" for this research. Additional tests of chemosensitizing agents are now being performed in the field on apples, by collaborators at Washington State University, and wheat, rice and potatoes, by collaborators at the All Russian Research Institute, Golitsino, Russia. This work supports NP 108 Component 2.1.4.


4.Accomplishments
1. Safe Natural Compounds Enhance Antifungal Activity of Commercial Fungicides and Antifungal Drugs. Fungal resistance to commercial antifungal agents presents a serious problem to both agriculture and medicine. USDA scientists in the Plant Mycotoxin Research Unit, Albany, CA identified a number of safe, natural products that significantly enhance effectiveness of commercial fungicides, such as strobilurin and fludioxonil. These natural compounds weaken the ability of fungi to build their cell walls or to respire normally. In collaboration with scientists at the Institute of Hygiene and Tropical Medicine, Lisbon, Portugal, chemo-sensitization was also found to be effective against a number of human pathogenic fungi. Chemosensitization enabled the use of antifungal drugs, such as itraconazole or fluconazole, against strains that had become resistant to these drugs. The use of this chemo-sensitization has promising potential in agriculture and medicine to help reduce environmental impact and costs of using fungicides and preventing or overcome resistance. This accomplishment relates to NP108, Component 2, Problem Statement D, Breeding Resistant Crops.

2. Safe Chemicals Prevent Aflatoxin Production: Antioxidants and Synthetic Amino Acids. Aflatoxin is a highly carcinogenic compound produced by certain fungi that infect a wide variety of edible agricultural products, such as peanuts, corn, tree nuts, and in some countries, wheat. In collaboration with scientists in the Food and Feed Safety Research Unit, New Orleans, LA, scientists in the Plant Mycotoxin Research Unit, Albany, CA found that antioxidants induce production of peroxiredoxins, enzymes that degrade certain oxygenated compounds in fungi, with a concomitant shutdown of the aflatoxin biosynthetic pathway. This finding is a major breakthrough in attempts to solve the aflatoxin contamination problem. This finding will lead to identification of natural compounds in crop plants that can suppress aflatoxin contamination. This accomplishment relates to NP108, Component 2, Problem Statement D, Breeding Resistant Crops.

3. Discovery of Analogs of Ferulic Acid as Potent Antifungal Agents. Fungal infections of agricultural products have a major impact on production, food quality and safety. Use of commercial fungicides is expensive and has an impact on the environment. Moreover, fungal pathogens are continuously developing resistance to commercial fungicides. USDA Scientists in the Plant Mycotoxin Research Unit, Albany, CA, have found a number of chemical compounds related to the natural compound, ferulic acid, have significant fungicidal activity. Some of these compounds show commercial promise and the structures of the compounds help us to understand how they work against the fungus. This accomplishment relates to NP108, Component 2, Problem Statement D, Breeding Resistant Crops.


5.Significant Activities that Support Special Target Populations
None


6.Technology Transfer

Number of Invention Disclosures Submitted1
Number of Non-Peer Reviewed Presentations and Proceedings2

Review Publications
Kim, J.H., Yu, J., Mahoney, N.E., Chan, K.L., Molyneux, R.J., Varga, J., Bhatnagar, D., Cleveland, T.E., Campbell, B.C. 2008. Elucidation of the functional genomics of antioxidant-based inhibition of aflatoxin biosynthesis. International Journal of Food Microbiology.122(1-2):49-60.

Yu, J., Ronning, C.M., Wilkinson, J.R., Campbell, B.C., Payne, G.A., Bhatnagar, D., Cleveland, T.E., Nierman, W.C. 2007. Gene profiling for studying the mechanism of aflatoxin biosynthesis in Aspergillus flavus and A. parasiticus. Journal of Food Additives & Contaminants. 24(10):1035-1042.

Kim, J.H., Mahoney, N.E., Chan, K.L., Molyneux, R.J., May, G.S., Campbell, B.C. 2008. Chemo-sensitization of fungal pathogens to antimicrobial agents using benzaldehyde analogs. Federation of European Microbiological Societies Microbiology Letters.281(1):64-72.

Kim, J.H., Campbell, B.C., Mahoney, N.E., Chan, K.L., Molyneux, R.J., May, G. 2008. Chemosensitization prevents tolerance of Aspergillus fumigatus to antimycotic drugs. Biochemical and Biophysical Research Communications.372(1):266-271.

Molyneux, R.J., Mahoney, N.E., Kim, J.H., Campbell, B.C. 2007. Mycotoxins in edible tree nuts. International Journal of Food Microbiology. 119:72-78

Lee, S., Lillehoj, H.S., Heckert, R.A., Chun, H., Cho, S., Tuo, W. 2008. Immunomodulatory Effects of Safflower Leaf (Carthamus tinctorius)on Chicken lymphocytes and macrophages. Journal of Poultry Science. 45:147-151

Rolshausen, P.E., Greve, L.C., Labavitch, J.M., Mahoney, N.E., Molyneux, R.J., Gubler, W.D. 2008. Pathogenesis of Eutypa lata in grapevine: Identification of virulence factors and biochemical characterization of cordon dieback. Journal of Phytopathology.98:222-229.

Santos, J.C., Riet-Correa, F.S., Dantas, A.F., Barros, S.S., Molyneux, R.J., Medeiros, R.M., Da Silva, D.M., De Oliveira, O.F. 2007.Toxic hepatopathy in sheep associated with the ingestion of the legume Tephrosia cinerea. Journal of Veterinary Diagnostic Investigation.19(6):690-694.

Molyneux, R.J., Lee, S.T., Gardner, D.R., Panter, K.E., James, L.F. 2007. Phytochemicals: The Good, the Bad, and the Ugly?. Phytochemistry.68(22-24):2973-2985.

Lee, S.T., Molyneux, R.J., Panter, K.E. 2007. Separation Of Enantiomeric Mixtures Of Alkaloids And Their Biological Evaluation. In: Bioactive Natural Products: Detection, Isolation, and Structural Determination, Second Edition, ISBN: 9780849372582, ISBN: 0849372585, Chpt. 7, pp. 209-219.

Barbosa, R.C., Riet-Correa, F., Lima, E.F., Medeiros, R.M., Guedes, K.M., Gardner, D.R., Molyneux, R.J., De Melo, L.E. 2007. Experimental swainsonine poisoning in goats ingesting Ipomoea sericophylla and Ipomoea riedelii (Convolvulaceae). Pesquisa Veterinaria Brasileira, 27(10):409-414.

Palumbo, J.D., O Keeffe, T.L., Mahoney, N.E. 2007. Inhibition of ochratoxin A production and growth of Aspergillus species by phenolic antioxidant compounds. Mycopathologia.164(5):241-248.

Last Modified: 9/20/2014
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