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Applied and Environmental Microbiology, November 2007, p. 7268-7276, Vol. 73, No. 22
0099-2240/07/$08.00+0     doi:10.1128/AEM.00801-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Aspergillus Volatiles Regulate Aflatoxin Synthesis and Asexual Sporulation in Aspergillus parasiticus{triangledown}

Ludmila V. Roze,1 Randolph M. Beaudry,2 Anna E. Arthur,1 Ana M. Calvo,6 and John E. Linz1,3,4,5*

Department of Food Science and Human Nutrition, Michigan State University,1 Department of Horticulture, Michigan State University,2 National Food Safety and Toxicology Center, Michigan State University,3 Department of Microbiology and Molecular Genetics, Michigan State University,4 Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan,5 Department of Biological Science, Northern Illinois University, DeKalb, Illinois6

Received 10 April 2007/ Accepted 9 September 2007

Aspergillus parasiticus is one primary source of aflatoxin contamination in economically important crops. To prevent the potential health and economic impacts of aflatoxin contamination, our goal is to develop practical strategies to reduce aflatoxin synthesis on susceptible crops. One focus is to identify biological and environmental factors that regulate aflatoxin synthesis and to manipulate these factors to control aflatoxin biosynthesis in the field or during crop storage. In the current study, we analyzed the effects of aspergillus volatiles on growth, development, aflatoxin biosynthesis, and promoter activity in the filamentous fungus A. parasiticus. When colonies of Aspergillus nidulans and A. parasiticus were incubated in the same growth chamber, we observed a significant reduction in aflatoxin synthesis and asexual sporulation by A. parasiticus. Analysis of the headspace gases demonstrated that A. nidulans produced much larger quantities of 2-buten-1-ol (CA) and 2-ethyl-1-hexanol (EH) than A. parasiticus. In its pure form, EH inhibited growth and increased aflatoxin accumulation in A. parasiticus at all doses tested; EH also stimulated aflatoxin transcript accumulation. In contrast, CA exerted dose-dependent up-regulatory or down-regulatory effects on aflatoxin accumulation, conidiation, and aflatoxin transcript accumulation. Experiments with reporter strains carrying nor-1 promoter deletions and mutations suggested that the differential effects of CA were mediated through separate regulatory regions in the nor-1 promoter. The potential efficacy of CA as a tool for analysis of transcriptional regulation of aflatoxin biosynthesis is discussed. We also identify a novel, rapid, and reliable method to assess norsolorinic acid accumulation in solid culture using a Chroma Meter CR-300 apparatus.

* Corresponding author. Mailing address: Department of Food Science and Human Nutrition, Michigan State University, 234B GM Trout Building, East Lansing, MI 48824. Phone: (517) 355-8474. Fax: (517) 353-8963. E-mail: jlinz{at}anr.msu.edu

{triangledown} Published ahead of print on 21 September 2007.

Applied and Environmental Microbiology, November 2007, p. 7268-7276, Vol. 73, No. 22
0099-2240/07/$08.00+0     doi:10.1128/AEM.00801-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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