Increased diuron resistance in the joint expression of mutations located at the DIU2, DIU3 and DIU4 loci of Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, diuron blocks the respiratory pathway at the level of the bc1 complex. Two mitochondrially inherited loci, DIU1 and DIU2, located in the cytochrome b gene, and two nuclearly inherited loci, DIU3 and DIU4, have previously been identified. The present work genetically characterizes two double mutants. One mutant, Diu-217, carries two nuclearly inherited mutations, diu3-217a and diu-217b; the second mutant, Diu-783, carries the previously described nuclear mutation diu3-783 and a mitochondrial mutation diu2-783. Each mutation, independent of its location, exhibits a weak diuron resistance. The joint expression of two or three mutations leads to a cumulative or a cooperative enhanced diuron-resistant phenotype.