AbstractBackgroundItraconazole is currently used to treat paracoccidioidomycosis. The mechanism of action of azoles has been elucidated in some fungi, although little is known regarding its mechanism of action inParacoccidioidesspp. The present work focused on identification of regulated transcripts using representational difference analysis ofParacoccidioidesspp. yeast cells treated with itraconazole for 1 and 2 h.ResultsParacoccidioides Pb01 genes up-regulated by itraconazole included genes involved in cellular transport, metabolism/energy, transcription, cell rescue, defense and virulence.ERG11,ERG6,ERG3,ERG5 andERG25 were up-regulated at multiple time points.In vivoinfection experiments in mice corroborated thein vitroresults. Ergosterol levels and distribution were evaluated inParacoccidioides Pb18 yeast cells, and the results demonstrate that both factors were changed in the fungus treated with itraconazole.ConclusionTo our knowledge, this is the first transcriptional analysis ofParacoccidioidesspp. exposed to a triazole drug. Here acetyl seems to be intensively produced from different metabolic pathways to produce ergosterol by the action of ergosterol synthesis related enzymes, which were also affected in other fungi. Among the genes affected, we identified genes in common with other fungi, as well as genes unique toParacoccidioides Pb01. Those genes could be considered target to new drugs. Voltage-gated Ca2+alpha subunit (CAV), Tetracycline resistance protein (TETA) and Hemolisyn-iii channel protein (HLYiii) were found only here and a probably involvement with resistence to itraconazole could be investigated in the future. However our findings do not permit inference to current clinical practice.