Submitted to: American Phytopathological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2005
Publication Date: 6/1/2005
Citation: Mcdonald, T., Brown, D.W., Keller, N.P., Hammond, T.M. 2005. RNA silencing of mycotoxin production in aspergillus and fusarium species. Molecular Plant-Microbe Interactions. 18:539-545. Interpretive Summary: Aspergillus and Fusarium are fungi that infect crops and cause a significant loss to farmers each year. They synthesis a number of toxins (aflatoxins and deoxynivalenol respectively) which can be found contaminating human and animal feeds and can cause a variety of animal and human diseases. A major focus of our labs is to identify strategies for reducing or eliminating mycotoxin contamination of wheat and corn. RNA silencing is a recently described biological process that we are exploring to see if it can work to shut down the synthesis of these fungal toxins. We have found that the RNA silencing of genes involved in mycotoxin biosynthesis prevents toxin synthesis, and in the case of F. graminearum, the toxin-minus strains caused less disease on wheat than wild type. The characterization of this phenomenon in Aspergillus and Fusarium indicates that RNA silencing technology may be a useful tool for eliminating mycotoxin contamination of agricultural products and may also lead to a better understanding of how these materials are made.
Technical Abstract: Mycotoxins are natural fungal products that are defined by their harmful affects on humans and animals. Aflatoxin contamination of maize by Aspergillus species and trichothecene contamination of small grains by Fusarium species are two of the most severe mycotoxin problems in the United States. We are investigating RNA silencing in an effort to identify novel ways to control mycotoxin contamination of crops. Transformation of two Aspergilli (A. flavus and A. parasiticus) and a Fusarium (F. graminearum) with inverted repeat transgenes (IRTs) containing sequences of mycotoxin-specific regulatory genes suppressed mycotoxin production in all three plant-pathogenic fungi. This atoxigenic phenotype was stable during infection on corn and wheat, and importantly, F. graminearum IRT strains were less virulent on wheat than wild type. The IRTs did not alter other physiological characteristics of the pathogenic fungi, such as spore production and growth rate on solid media. These results indicate that RNA silencing exists in Aspergillus and Fusarium plant pathogens and suggests that RNA silencing technology may be a useful tool for eliminating mycotoxin contamination of agricultural products.