Saccharomyces cerevisae and Arabidopsis thaliana: Useful Model Systems for the Identification of Molecular Mechanisms Involved in Resistance of Plants to Toxins

Secondary metabolites produced by pathogens during the infection process are thought to play a role as pathogenicity or virulence determinants in many plant diseases. Baker's yeast and the plant Arabidopsis thaliana are attractive models for elucidating molecular mechanisms of resistance to toxic substances. For the Fusarium mycotoxin deoxynivalenol, the following resistance mechanisms were identified in yeast: (1) reduced toxin uptake due to the ABC transporter protein Pdr5p (molecular efflux pump), (2) detoxification by the acetyltransferase Ayt1p, and (3) modification of the ribosomal target by amino acid changes in the ribosomal protein L3 (Rpl3p). PDR5-like genes exist in plant genomes as large gene families and could play an important role as a first line of defence against a broad range of toxic metabolites. Amino acid alterations in the highly conserved RPL3 genes could likewise play a role in trichothecene resistance in plants. The knowledge obtained using model systems should be valuable in biotechnological approaches to disease control and marker-assisted resistance breeding.