Figure 2.

Loss of HIR1 phenocopies deletion of EFG1. (A) Simplified scheme of the major signaling cascades regulating the hyphal transcriptional program. The MAPK cascade and the cAMP/PKA pathway activate transcription factors such as Efg1 and Cph1 to initiate HSG expression. Additionally, transcriptional repressors such as Nrg1 and Tup1 control HSG expression and are themselves regulated by upstream signaling cascades such as cAMP/PKA. (B) Reduction in NRG1 gene dosage alleviates hyphal formation defects of hir1Δ/Δ cells on solid medium. Colony morphology was inspected after 3 days at 37 °C. Scale bar corresponds to 1 mm. (C) NRG1 downregulation is independent of EFG1, CPH1 and HIR1. Gene expression of NRG1 and ECE1 was measured after 30 min of hyphal induction in YPD with 10% FCS by RT-qPCR. Transcript levels were normalized to the expression of the reference gene RIP1. Data are presented as mean + SD of three independent experiments. (D) Reduction of NRG1 gene dosage does not affect efg1∆/∆ hyphal formation. Colony morphology was assessed after 3 days at 37 °C. Scale bar corresponds to 1 mm. (E) Loss of HIR1 partially phenocopies efg1Δ/Δ under embedded growth conditions. Colony pictures were taken after 5 and 7 days at 25 °C. Scale bar corresponds to 1 mm. (F) HIR1 mutant cells are irresponsive to exogenous cAMP supplementation. Colony morphology was assessed after 3 days at 37 °C. Scale bar corresponds to 1 mm.