Figure 5: TFs regulating sterol biosynthesis genes govern general environmental stress responses and adaptation in C. neoformans.

(a) TF mutants showing opposite patterns of susceptibility to fluconazole (FCZ) and amphotericin B (AmpB). WT strain H99 and TF mutants grown overnight were 10-fold serially diluted (1 to 10⁴), and then spotted onto YPD containing the following antifungal drugs: 15 μg ml⁻¹ FCZ or 1.5 μg ml⁻¹ AmpB. (b) Northern blot analysis was performed with a ERG11-specific probe and the total RNA in cells treated or not treated with 10 μg ml⁻¹ FCZ. (c) Northern blot assay was performed with ERG gene-specific probes. Quantitative reverse transcription–PCR analysis was performed with each ERG gene-specific primer using complementary DNA synthesized from the total RNA in cells treated or not treated with 10 μg ml⁻¹ FCZ. Duplicate technical experiments with two or more biological samples were performed. Representative images from independent experiments for each ERG gene are shown. Error bars indicate s.d. (d) The role of Sre1 and Hob1 in environmental stress responses and adaptations. Strains grown as described in a were spotted onto YPD containing the stress-inducing agents: 3.5 mM H₂O₂, 2.5 mM diamide, 0.3 μg ml⁻¹ tunicamycin (TM), 15 mM dithiothreitol (DTT), 5 mg ml⁻¹ calcofluor white (CFW), 0.03% SDS, 0.04% methyl methanesulfonate (MMS) or 100 mM hydroxyurea (HU). (e) The proposed model for the role of Sre1 and Hob1 in the sterol homeostasis and general stress responses of C. neoformans.