Overexpression of membrane efflux transporters causing multidrug resistance in field isolates of Botrytis cinerea

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In French and German wine-growing regions, increasing Botrytis cinerea populations with multidrug resistance (MDR) phenotypes have been observed. We have identified mutations in MDR strains leading to the overexpression of efflux transporters. In MDR1 strains, gain-offunction mutations in the transcription factor Mrr1 are leading to its activation and thus overexpression of the ABC transporter encoding gene atrB. We also want to investigate the specificity and mechanism of the Mrr1-dependent atrB induction, and to identify the binding site of Mrr1 in the atrB promoter. Using microarray-based transcriptome analyses, we want to identify all Mrr1-regulated genes. In MDR2 strains, two promoter rearrangement mutations caused by retroelement sequences have been identified in the MFS transporter gene mfsM2. We want to confirm the hypothesis that the spread of MDR2 strains has occurred clonally from two ancestor cells, and that one of the mutations have migrated from French into German wine-growing regions. In strawberry fields, we have recently observed a novel and stronger, MDR1-like phenotype (called MDR1*) and we want to identify the underlying mutation(s).