Plant-derived essential oils with monoterpenoids have been used as antifungal drugs since ancient times, but the mode of action of these natural hydrocarbons at the molecular level is not understood. In order to understand the mechanisms of toxicity of α-terpinene (a cyclic monoterpene), a culture of Saccharomyces cerevisiae was exposed to 0.02% α-terpinene for 2 h and transcript profiles were obtained using yeast DNA arrays. These profiles, when compared with transcript profiles of untreated cultures, revealed that the expression of 793 genes was affected. For 435 genes, mRNA levels in treated cells compared with control cells differed by more than two-fold, whereas for 358 genes, it was <0.5-fold. Northern blots were performed for selected genes to verify the microarray results. Functional analysis of the up-regulated genes indicates that, similar to commonly used antifungal drugs, α-terpinene exposure affected genes involved in ergosterol biosynthesis and sterol uptake. In addition, transcriptional induction of genes related to lipid metabolism, cell wall structure and function, detoxification and cellular transport was observed in response to terpinene toxicity. Notably, the functions of 192 up-regulated genes are still unknown, but their characterization will probably shed light on the mechanisms of drug resistance and sensitivity. Taken together, this study showed that α-terpinene has strong antifungal activities and its modes of action resemble those of presently used antifungal drugs.

Me₂SO is a polar solvent that is widely used in biochemistry, pharmacology, and industry. Although there are several reports in the literature concerning the biological effects of Me₂SO, the total cellular response remains unclear. In this paper, DNA microarray technology combined with the hierarchical clustering bioinformatics tool was used to assess the effects of Me₂SO on yeast cells. We found that yeast exposed to Me₂SO increased phospholipid biosynthesis through up-regulated gene expression. It was confirmed by Northern blotting that the level of INO1 and OPI3 gene transcripts, encoding key enzymes in phospholipid biosynthesis, were significantly elevated following treatment with Me₂SO. Furthermore, the phospholipid content of the cells increased during exposure to Me₂SO as shown by conspicuous incorporation of a lipophilic fluorescent dye (3,3′-dihexyloxacarbocyanine iodide) into the cell membranes. From these results we propose that Me₂SO treatment induces membrane proliferation in yeast cells to alleviate the adverse affects of this chemical on membrane integrity.