Saccharomyces cerevisiaehas been used as a model system to characterize the effect of cytochromebmutations found in fungal and oomycete plant pathogens resistant to Qo inhibitors (QoIs), including the strobilurins, now widely employed in agriculture to control such diseases. Specific residues in the Qosite of yeast cytochromebwere modified to obtain four new forms mimicking the Qobinding site of Erysiphe graminis, Venturia inaequalis, Sphaerotheca fuligi-neaandPhytophthoramegasperma. Thesemodified versions of cytochromebwere then used to study the impact of the introduction of the G143A mutation on bc1 complex activ-ity. .
