The widespread pleiotropic drug resistance (PDR) phenomenon is well described as the long term selection of
genetic variants expressing constitutively high levels of membrane transporters involved in drug efflux.
However, the transcriptional cascades leading to the PDR phenotype in wild-type cells are largely unknown and the first
steps of this phenomenon are poorly understood. We investigated the transcriptional mechanisms underlying the establishment
of an efficient PDR response in budding yeast. We show that, within a few minutes of drug sensing, yeast elicits an
effective PDR response, involving tens of PDR genes. This early PDR (ePDR) response is highly dependent on the Pdr1p
transcription factor, which is also one of the major genetic determinants of long-term PDR acquisition.
The activity of Pdr1p in early drug response is not drug-specific, as two chemically unrelated drugs, benomyl and
fluphenazine, elicit identical, Pdr1p-dependent, ePDR patterns. Our data also demonstrate that Pdr1p is an original
stress response factor, the DNA-binding properties of which do not depend on the presence of drugs. Thus, Pdr1p is a
promoter-resident regulator involved in both basal expression and rapid drug-dependent induction of PDR genes.