Multi-drug-resistance (MDR) in septoria leaf blotch.
Résumé
Multidrug resistance (MDR) is a common trait developed by many organisms to counteract chemicals and/or drugs. The basic MDR mechanism relies on an overexpressed efflux transport system that actively expulses the toxic agent. MDR strains were detected in Zymoseptoria tritici field populations since 2008. These strains are cross resistant to fungicides with different modes of action and may threaten the efficacy of fungicide treatments.
We have shown that this resistance is due to active fungicide efflux, potentially through the overexpression of one membrane transporter gene, MgMFS1. The inactivation of MgMFS1 abolished the MDR phenotype in at least one field strain. A bulk-segregant analysis (BSA) of two MDR isolates coupled to next generation sequencing showed a clear co-segregation between the MDR phenotype and the left arm of chromosome 7 covering MgMFS1. We identified a 519 bp insert (LTR-like) in both MDR strains as well as in other MDR field strains. Genotyping of the progenies for the promoter insert showed a clear, but not exclusive correlation between the MgMFS1 promoter insert and the MDR phenotype. Current investigations are underway to analyze if the LTR-like insert - alone or in combination with a second mutation - confers the MDR phenotype through MgMFS1 overexpression.