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PMR News
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Overcoming antifungal drug resistance by using natural compounds. PMR scientists have shown that natural compounds can act as chemosensitizers for drug-resistant strains of pathogenic fungi. The findings were presented at Focus on Fungal Infections 18, an international conference on treatment of human pathogenic fungal diseases, in San Antonio, TX, Mar 5-7, 2008. The poster, "Overcoming antifungal drug resistance using chemosensitization: Targeting stress response pathways of fungi with benzo analogs", won the Thomas J. Walsh Clinical Mycology Award for the most innovative and outstanding achievement in the field of research on infectious fungal diseases at the conference. (Poster is available in PDF format here.) This marks the first time that non-medical researchers were recognized. Initially, PMR scientists developed the chemosensitization concept for agricultural fungal pathogens (see next item). The gene targets (stress response pathways) were determined by using fungal mutants provided by Gregory S. May, Division of Pathology and Laboratory Medicine, MD Anderson Cancer Center, University of Texas, Houston. Several natural compounds were tested against drug-resistant strains of clinical fungal pathogens, in combination with commercial antifungal drugs. This work was done in collaboration with Natalia C. G. Faria, at the Institute of Hygiene and Tropical Medicine, New University of Lisbon, Portugal. The co-application of natural compounds with antifungal drugs significantly reduced the dosages needed to inhibit growth of the clinical strains. Lower effective dosages should lower costs and potential negative side effects, and may also reduce the potential for development of resistance in the fungi to new antifungal agents. The results on chemosensitization of Aspergillus fumigatus have been published in Biochemical and Biophysical Research Communications 372: 266-271, 18 July 2008. This paper was also highlighted in the July 2008 issue of the Aspergillus Newsletter in the Latest News and Articles section here.
PMR is seeking potential research collaborators and commercial partners (agricultural or medical) on use of chemosensitization to improve efficacy of antifungal agents. Please contact our technology transfer office for details.
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Natural chemicals found that enhance antifungal activity of commercial fungicides. PMR scientists have discovered a number of natural phenolic compounds that improve the antifungal activity of commercial fungicides. These phenolics act as chemosensitizing agents that disrupt the fungal cell in response to stress. Such chemosensitizing enhancement has been found to be effective against pre- and post-harvest fungal pathogens of fruits, such as apples and oranges. Reprint is available: FEMS Microbiology Letters 281: 64-72.
Invention Report filed and accepted Feb 2008
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Antioxidants control genes that suppress aflatoxin biosynthesis. PMR scientists, in collaboration with ARS scientists from New Orleans and the J. Craig Venter Institute, have found a group of genes, peroxiredoxins, that can shut down aflatoxin biosynthesis. Previously, PMR scientists discovered that certain natural antioxidants, such as gallic acid, could prevent aflatoxin biosynthesis ( Mahoney and Molyneux 2004). Using a recently available genetic tool called microarray analysis, the collaborating team of scientists were able to show that antioxidants turned on this group of genes. Peroxiredoxins remove signals that trigger aflatoxin biosynthesis. This discovery allows development of strategies to regulate these genes so that aflatoxin is not produced when the fungus infects certain agricultural products, such as peanuts, corn, cotton and tree nuts. Reprint is available: Int'l J. Food Microbiology 122: 49-60.
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Eutypa dieback symptoms on grapevine include stunted shoots and leaf development. See right side of foliage.
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Pathogenesis of Eutypa in grapevine. PMR scientists, in collaboration with scientists at the University of California, Davis, recently received the "Editor's Pick"in the journal Phytopathology. The Editor-in-Chief, Dr. Robert Gilbertson, selected their paper ( Phytopathology 98: 222-229, 2008) noting that "new insight into the mechanism by which the vascular pathogen, Eutypa lata, infects and causes disease is revealed by examining the grapevine wood polymers degraded and enzymes and secondary metabolites produced by the fungus. The results revealed a possible mechanism of disease tolerance in grapevine, and raised important new questions about fungal colonization of woody hosts."
Related PMR Eutypa publications: 2003, 2004, 2005, 2006a, 2006b
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Wheat kernel image (left);
1D signal (right)
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One dimensional x-ray inspection. PMR engineers have designed a simplified version of a linescan x-ray unit with the goal of performing food inspection tasks without the hassle and expense of a full scale machine.With this new technology, a one dimensional signal replaces the traditional two dimensional image. For certain inspection tasks this arrangement has been shown to be equal or superior to traditional imaging in terms of the ability to detect defects or contaminants. This new technology is being applied to a number of inspection tasks, including the detection of pits in cherries and insect infestation in wheat.
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Large-scale VOC collection
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In situ volatile organic compound collections. In collaboration with Paramount Farming Company and the Almond Board of California, PMR researchers have designed and implemented small-scale and large-scale volatile organic compound (VOC) collection systems. These systems are capable of monitoring VOC emissions directly from almonds (or other analytes) intact on the tree (in situ analysis). The small-scale collection system utilizes solid-phase microextraction (SPME) to adsorb the VOCs, while the large-scale system utilizes Tenax as the absorbent medium. Both systems incorporate customized, inert collection bags designed by PMR scientists. VOCs collected via these systems can be analyzed via a gas chromatogram coupled to a mass spectrometer (GC-MS), and/or used in bioassays with an electroantennogram detector (EAG) and the navel orangeworm moth.
Related PMR VOC collection publications: 2007, 2008, 2009, 2011
EAG video: 2012
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Flight tunnel bioassay
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Specific behavioral bioassays are being used to determine both adult moth (arousal, orientation to traps in cages, and flight tunnel) and larval worm (orientation arenas and servo-sphere) sensitivity and attraction to candidate VOCs. Identified attractants will be developed into lure formulations for monitoring and "attract and kill" control tactics against both adults and larvae.
An ARS Research Associate proposal stemming from PMR's VOC research, "Method Development to Identify Natural Chemical Lures for Control of Navel Orangeworm and Light Brown Apple Moth," has been selected for headquarters' funding.
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Industrially important hydrocarbon captured as a volatile from an almond hull fungus. While investigating the volatile emission of almond hulls and fungi from almond hulls, PMR scientists have discovered a fungus that produces relatively large quantities of styrene - an industrially important chemical used in many plastics. This strain of Fusarium oxysporum could be used as a potential green source of a vital commercial chemical. The discovery, and methods to perform large-scale production and isolation, have been published in the Journal of Agricultural and Food Chemistry 56(23):11392-11398. Abstract is available here.
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Navel orangeworm larva among Aspergillus spores
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Navel orangeworm activity can promote aflatoxin contamination of almonds. A major insect pest of almonds, the navel orangeworm, has been found by PMR scientists to be a major contributor to promoting infection of almonds by the fungus that produces aflatoxin. This insect can carry the spores of this fungus (Aspergillus) to the almond kernel. The spores can then infect the almond through feeding wounds produced by the insect. Funding for this pilot study was provided by the Almond Board of California. The research was presented at the 2008 APS Centennial Meeting in Minneapolis. Abstract is available here.
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A research collaboration involving Dr. Bruce Campbell, Research Leader, and two Russian scientists, Dr. Vitaly Dzhavakhiya (Russian Research Institute of Phytopathology, VNIIF) and Dr. Radii Khomutov (Russian Academy of Sciences, Moscow) has been funded by the ARS Office of International Research Programs (OIRP). The project is established under OIRP's Former Soviet Union Scientific Cooperation Program. The research will focus on novel approaches to reduce fungal infection and mycotoxin biosynthesis by using new, safe methods that target polyketide synthase and antioxidative stress-response systems of fungi. You may read more about this collaboration in this ARS News release: "New Pairs of Compounds May Help Tree Nuts Fight Fungal Foe."
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Meetings |
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Jan 15-20, 2012 |
Fungal Pathogens: From Basic Biology to Drug Discovery (Keystone Symposia Global Health Series)
Santa Fe, NM |
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Jan 25-27, 2012 |
Walnut Research Conference
Bodega, CA |
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Jan 29-Feb 3, 2012 |
Gordon Research Conference on Plant Volatiles
Ventura, CA |
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Jun 16-19, 2012 |
112th General Meeting: American Society for Microbiology
San Francisco, CA |
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Press |
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- "Fruit fly research, maligned by Sarah Palin, bears fruit "- ScientificAmerican.com, Feb 26, 2009
- "New science could combat cancer compound in nuts"- Food Navigator-USA.com, Oct 11, 2006
- "Chemical in Walnuts, Fungal Gene Studies Could Reduce Aflatoxin Risks"- ASM News, Volume 71, Number 6, 2005
Agricultural Research- USDA's science magazine, published monthly by the ARS Information Staff ( magazine homepage):
Also see footer for additional ARS Information Staff articles featuring PMR's research. |
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Awards |
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The 2007 ARS Administrator's Outreach, Diversity and Equal Opportunity Award was presented Feb. 12, 2008 in Washington, DC. Several PMR scientists were among those recognized for their participation as mentors in the SF Works internship program at the Western Regional Research Center: John Beck, Bruce Campbell, Ron Haff, Sylvia Hua, Eric Jackson and Jeff Palumbo. |
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Congratulations to Flo Ankersmit, Program Support Assistant, for being selected as the 2008 ARS Pacific West Area's Secretarial/Clerical Employee of the Year. Flo has handled primary secretarial responsibilities for both the PMR and Exotic and Invasive Weeds Research Units. |
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