Although it has been well established that ambient pH affects the growth, physiology, differentiation, and viability of all organisms, the molecular responses to environmental pH changes are only now being elucidated. In Aspergillus nidulans and other fungi these responses are mediated by gene pacC, which codes for a Zn-finger transcription factor that activates the expression of several genes at alkaline pH. The pacC transcription is itself induced under alkaline growth conditions. In order to investigate the role of thepacC gene in the adaptive response of the dermatophyte Trichophyton rubrum to ambient pH, an important event in the dermatophyte-host interactions, we have cloned and identified a gene of this fungus homologous to the pacC gene of A. nidulans and pacC-1 of N. crassa (GenBank-access number: AF363788). The northern and western blots of T. rubrum also showed an increase of pacC transcripts at alkaline pH. For disruption, the promoter and first zinc-finger (3.5 Kb) were removed in the genomic clone of 6.0 Kb and replaced with the hygromycin phosphotransferase gene (hph), which confers drug resistance on eukaryotic cells. Several transformants of T. rubrum were isolated and showed that growth, conidiation, and pigmentation of the colonies were affected by the disruption of gene pacC, as already observed for C. albicans and N. crassa, indicating that surviving a proton attack depends on the expression of genes (e.g. pacC gene) that determine sensitivity or resistance to pH. Furthermore, these mechanisms are apparently involved in the installation, development, and survival of dermathophytes in humans. Financial support: FAPESP, CNPq, CAPES, FAEPA and Reitoria-USP.
Fungal Genet. Newsl. 50 (Supl):abstract
Full conference title:
22nd Fungal Genetics Conference
- Fungal Genetics Conference 22nd (2001)