Yeast as a Model for the Study of Fusarium graminearum Resistance

Abstract

Fusarium graminearum trichothecene mycotoxins, notably deoxynivalenol (DON), contaminate cereal grains and threaten food and feed safety. This study identified the ATP-binding cassette (ABC) transporter Pdr5p as the main exporter of DON in the model system Saccharomyces cerevisiae. Toxin export by Pdr5p from living cells was, however, blocked by an unidentified inhibitory compound produced by F. graminearum. The main objective of this study was to create Pdr5p mutants demonstrating insensitivity to inhibition while maintaining the ability to export DON. A total of 38 Pdr5p mutants, each containing a single amino acid substitution at two important sites of the transporter, were generated and expressed in yeast harboring a deletion of wild-type Pdr5p. This study demonstrated that while most of these mutants maintained DON export, some were more resistant than the wild-type to inhibition by the Pdr5p-specific inhibitors FK506 and enniatin B. Results suggest that Pdr5p mutants S1360D and S1360E are resistant to F. avenaceum culture filtrate while none of the 38 mutants analyzed are resistant to F. graminearum culture filtrate. This study has shown that knowledge gained though the study of Pdr5p mutants in yeast could be extended to plants in an attempt to improve their ability to confer resistance to Fusarium species.