A basic‐region helix–loop–helix protein‐encoding gene (devR) involved in the development of Aspergillus nidulans

• Published in: Molecular microbiology 2004-04, Vol.52 (1), p.227-241
• Main Authors: Tüncher, André, Reinke, Hans, Martic, Goran, Caruso, Maria Louise, Brakhage, Axel A.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Aspergillus nidulans; Aspergillus nidulans - cytology; Aspergillus nidulans - genetics; Aspergillus nidulans - growth & development; Aspergillus nidulans - metabolism; Biological and medical sciences; Cell Nucleus; Cloning, Molecular; Culture Media - chemistry; Cytoplasm; DNA, Fungal - chemistry; DNA, Fungal - isolation & purification; Fundamental and applied biological sciences. Psychology; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - physiology; Gene Deletion; Genes, Fungal; Genes, Reporter; Green Fluorescent Proteins; Helix-Loop-Helix Motifs; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Microbiology; Miscellaneous; Molecular Sequence Data; Mycology; Pigments, Biological - biosynthesis; Potassium Chloride - metabolism; Protein Kinases - genetics; Protein Kinases - physiology; Protein Transport; RNA, Messenger - analysis; Sequence Alignment; Sequence Analysis, DNA; Signal Transduction; Transcription Factors - genetics; Transcription Factors - physiology
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2003.03961.x

Summary Basic‐region helix–loop–helix (bHLH) proteins form an interesting class of eukaryotic transcription factors often involved in developmental processes. Here, a so far unknown bHLH protein‐encoding gene of the filamentous ascomycete Aspergillus nidulans was isolated and designated devR for regulator of development. Deletion of devR revealed that the gene is non‐essential for vegetative growth. However, the deletion mutant produced wrinkled colonies, a yellow pigment and did not form conidia on minimal agar plates. Conidiophore development was initiated normally, and colonies produced conidiophores with metulae and phialides. However, the phialides continued to grow filamentously and produced a second conidiophore with a vesicle at its end. The addition of KCl (0.6 M) to the medium suppressed the knock‐out phenotype. The ΔdevR phenotype resembled that of a mutation in the tcsA gene encoding a histidine kinase domain and a response regulator domain. Here, we generated a tcsA deletion mutant. In a ΔtcsA strain, a DevR–Egfp protein fusion was detected in the cytoplasm, whereas in the wild type, the protein fusion was exclusively located in the nuclei, indicating that TcsA is required for nuclear localization of DevR. devR mRNA steady‐state levels were similar in sporulating and vegetatively growing mycelia, and independent of a functional brlA gene. Moreover, under all conditions tested, self‐crossing of the ΔdevR mutant strain was never observed. Taken together, devR encodes a bHLH regulatory protein that is part of the tcsA signal transduction network and required for development under standard growth conditions.