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

Toxins

Ludmila V. Roze²  Maris Laivenieks³  Sung-Yong Hong²  Josephine Wee²  Shu-Shyan Wong²  Benjamin Vanos²  Deena Awad²  Kenneth C. Ehrlich¹  John E. Linz² 

[1] Southern Regional Research Center, Agricultural Research Service, USDA, New Orleans, LA 70124, USA; E-Mail:;Department of Food Science and Human Nutrition, Michigan State University (MSU), East Lansing, MI 48824, USA; E-Mails:;Department of Microbiology and Molecular Genetics, Michigan State University (MSU), East Lansing, MI 48824, USA; E-Mail:

关键词: Aspergillus parasiticus;    oxidative stress;    secondary metabolism;    aflatoxin;    endosomes;    redox signaling;   

DOI  :  10.3390/toxins7051411

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.