title: SclR, a basic helix-loop-helix transcription factor, regulates hyphal morphology and promotes sclerotial formation in Aspergillus oryzae.
abstract: Most known basic-region helix-loop-helix (bHLH) proteins belong to a superfamily of transcription factors often involved in the control of growth and differentiation. Therefore, inappropriate expression of genes encoding bHLH proteins is frequently associated with developmental dysfunction. In our previously reported study, a novel bHLH protein-encoding gene (AO090011000215) of Aspergillus oryzae was identified. The gene-disrupted strain was found to produce dense conidia, but sparse sclerotia, relative to the parent strain. Here, to further analyze its function, we generated an overexpressing strain using the A. oryzae amyB gene promoter. Genetic overexpression led to a large number of initial hyphal aggregations and then the formation of mature sclerotia; it was therefore designated sclR (sclerotium regulator). At the same time, the sclR-overexpressing strain also displayed both delayed and decreased conidiation. Scanning electron microscopy indicated that the aerial hyphae of the sclR-overexpressing strain were extremely branched and intertwined with each other. In the generation of the SclR-enhanced green fluorescent protein (EGFP) expression strain, the SclR-EGFP protein fusion was conditionally detected in the nuclei. In addition, the loss of sclR function led to rapid protein degradation and cell lysis in dextrin-polypeptone-yeast extract liquid medium. Taken together, these observations indicate that SclR plays an important role in hyphal morphology, asexual conidiospore formation, and the promotion of sclerotial production, even retaining normal cell function, at least in submerged liquid culture.
authors.affiliation: Noda Institute for Scientific Research, 399 Noda, Noda City, Japan.
authors.forename: Feng Jie
authors.initials: FJ
authors.lastname: Jin
authors.forename: Tadashi
authors.initials: T
authors.lastname: Takahashi
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Matsushima
authors.forename: Seiichi
authors.initials: S
authors.lastname: Hara
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Shinohara
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Maruyama
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamoto
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Koyama
mesh_terms: D001236:Aspergillus oryzae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D055786:Gene Knockout Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D025301:Hyphae / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D013172:Spores, Fungal / Q000235:genetics / Q000502:physiology*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D017931:DNA Primers; D005656:Fungal Proteins; D049452:Green Fluorescent Proteins; C485184:enhanced green fluorescent protein