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Open AccessArticle

Aflatoxin Biosynthesis Is a Novel Source of Reactive Oxygen Species—A Potential Redox Signal to Initiate Resistance to Oxidative Stress?

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Department of Food Science and Human Nutrition, Michigan State University (MSU), East Lansing, MI 48824, USA
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Department of Plant Biology, Michigan State University (MSU), East Lansing, MI 48824, USA
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Department of Microbiology and Molecular Genetics, Michigan State University (MSU), East Lansing, MI 48824, USA
4
Southern Regional Research Center, Agricultural Research Service, USDA, New Orleans, LA 70124, USA
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Center for Integrative Toxicology, Michigan State University (MSU), East Lansing, MI 48824, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Jiujiang Yu
Toxins 2015, 7(5), 1411-1430; https://doi.org/10.3390/toxins7051411
Received: 5 February 2015 / Revised: 15 April 2015 / Accepted: 17 April 2015 / Published: 28 April 2015
Aflatoxin biosynthesis in the filamentous fungus Aspergillus parasiticus involves a minimum of 21 enzymes, encoded by genes located in a 70 kb gene cluster. For aflatoxin biosynthesis to be completed, the required enzymes must be transported to specialized early and late endosomes called aflatoxisomes. Of particular significance, seven aflatoxin biosynthetic enzymes are P450/monooxygenases which catalyze reactions that can produce reactive oxygen species (ROS) as byproducts. Thus, oxidative reactions in the aflatoxin biosynthetic pathway could potentially be an additional source of intracellular ROS. The present work explores the hypothesis that the aflatoxin biosynthetic pathway generates ROS (designated as “secondary” ROS) in endosomes and that secondary ROS possess a signaling function. We used specific dyes that stain ROS in live cells and demonstrated that intracellular ROS levels correlate with the levels of aflatoxin synthesized. Moreover, feeding protoplasts with precursors of aflatoxin resulted in the increase in ROS generation. These data support the hypothesis. Our findings also suggest that secondary ROS may fulfill, at least in part, an important mechanistic role in increased tolerance to oxidative stress in germinating spores (seven-hour germlings) and in regulation of fungal development. View Full-Text
Keywords: Aspergillus parasiticus; oxidative stress; secondary metabolism; aflatoxin; endosomes; redox signaling Aspergillus parasiticus; oxidative stress; secondary metabolism; aflatoxin; endosomes; redox signaling
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Roze, L.V.; Laivenieks, M.; Hong, S.-Y.; Wee, J.; Wong, S.-S.; Vanos, B.; Awad, D.; Ehrlich, K.C.; Linz, J.E. Aflatoxin Biosynthesis Is a Novel Source of Reactive Oxygen Species—A Potential Redox Signal to Initiate Resistance to Oxidative Stress? Toxins 2015, 7, 1411-1430.

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