title: AoRim15 is involved in conidial stress tolerance, conidiation and sclerotia formation in the filamentous fungus Aspergillus oryzae.
abstract: The serine-threonine kinase Rim15p is a master regulator of stress signaling and is required for stress tolerance and sexual sporulation in the yeast Saccharomyces cerevisiae. However, in filamentous fungi that reproduce asexually via conidiation, the physiological function of Rim15p homologs has not been extensively analyzed. Here, we functionally characterized the protein homolog of Rim15p in the filamentous fungus Aspergillus oryzae, by deleting and overexpressing the corresponding Aorim15 gene and examining the role of this protein in stress tolerance and development. Deletion of Aorim15 resulted in an increase in the sensitivity of conidia to oxidative and heat stresses, whereas conidia of the Aorim15 overexpressing strain were more resistant to these stresses. These results indicated that AoRim15 functions in stress tolerance, similar to S. cerevisiae Rim15p. Phenotypic analysis revealed that conidiation was markedly reduced by overexpression of Aorim15 in A. oryzae, and was completely abolished in the deletion strain. In addition, the formation of sclerotia, which is another type of developmental structure in filamentous fungi, was decreased by the deletion of Aorim15, whereas Aorim15 overexpression increased the number of sclerotia. These results indicated that AoRim15 is a positive regulator of sclerotia formation and that overexpression of AoRim15 shifts the developmental balance from conidiation towards sclerotia formation. Collectively, we demonstrated that AoRim15 is involved in the stress tolerance of conidia and differentially regulates between the two developmental fates of conidiation and sclerotia formation.
authors.affiliation: Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Nakamura
authors.affiliation: Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuma
authors.affiliation: Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Feng Jie
authors.initials: FJ
authors.lastname: Jin
authors.affiliation: Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. Electronic address: amarujun@mail.ecc.u-tokyo.ac.jp.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Maruyama
authors.affiliation: Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamoto
mesh_terms: D001236:Aspergillus oryzae / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D015398:Signal Transduction; D013172:Spores, Fungal / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D017346:Protein Serine-Threonine Kinases
keywords: Aspergillus oryzae; Conidia; Development; Sclerotia; Stress