Sensitivity assays with yeast mutants
Cells were grown overnight in YPD broth (pH 7.0, MOPS buffered) until the optical density of 3.0 at A600 was reached. For mutants, G418 at the concentration of 200 μg/ml was added to the broth. Seven serial 1:5 dilutions of the overnight cultures were prepared in appropriate medium and plated on YPD agar containing either 110 μM of pterostilbene or 1% DMSO as control. The plates were photographed after incubating for 2 days at 30°C.
Results
IC50 determination in S. cerevisiae
Pterostilbene is known to possess strong antifungal activity [16]. In this study, in order to investigate how pterostilbene functions in fungal cells, we determined the consequences of exposure to this compound by monitoring the whole-genome transcriptional response in the model yeast Saccharomyces cerevisiae. We made use of S. cerevisiae since it has been extensively used for elucidating the molecular targets of antifungal and therapeutic compounds (reviewed in [26,27]). We first determined the IC50 value for pterostilbene in S. cerevisiae cells using a combination of microplate-based and large-scale culture assays as previously described [18]. The IC50 was determined to be 70 μM based on the average value from four independent experiments (Figure (Figure1),1), and this concentration was used for subsequent microarray studies.