title: Expression of ustR and the Golgi protease KexB are required for ustiloxin B biosynthesis in Aspergillus oryzae.
abstract: Ustiloxin B, originally isolated from the fungus Ustilaginoidea virens, is a known inhibitor of microtubule assembly. Ustiloxin B is also produced by Aspergillus flavus and is synthesized through the ribosomal peptide synthesis pathway. In A. flavus, the gene cluster associated with ustiloxin B production contains 15 genes including those encoding a fungal C6-type transcription factor and ustiloxin B precursor. Although the koji mold Aspergillus oryzae, which is genetically close to A. flavus, has the corresponding gene cluster, it does not produce ustiloxin B, which may be explained by the fact that the gene encoding the transcription factor UstR is not expressed. Here, to investigate whether ustiloxin B can be produced by expressing ustR in A. oryzae, we constructed ustR expression (ustR (EX)) strains and analyzed ustiloxin B production. In the ustR (EX) strains, all genes in the cluster were up-regulated, in line with expression of ustR, and ustiloxin B produced. To elucidate whether the KexB protease is involved in the processing of the ustiloxin B precursor protein UstA, which has repeats of basic amino acid doublets resembling KexB target sites, we also constructed a ustR (EX) strain with the ∆kexB genotype. Although ustR was expressed in this strain, ustiloxin B was barely detectable. This finding strongly suggests that KexB is required for ustiloxin B production.
authors: ABE-project, New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8579, Japan.
authors: Akira
authors: A
authors: Yoshimi
authors: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 17-2-1 Higashi-Nijo, Tsukisamu, Toyohira-ku, Sapporo, Hokkaido, 062-8517, Japan.
authors: Myco
authors: M
authors: Umemura
authors: Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan.
authors: Nozomi
authors: N
authors: Nagano
authors: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan.
authors: Hideaki
authors: H
authors: Koike
authors: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 17-2-1 Higashi-Nijo, Tsukisamu, Toyohira-ku, Sapporo, Hokkaido, 062-8517, Japan.
authors: Masayuki
authors: M
authors: Machida
authors: ABE-project, New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8579, Japan. kabe@niche.tohoku.ac.jp.|Laboratory of Applied Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Sciences, Tohoku University, 1-1 Amamiya, Tsutsumi-dori, Sendai, Miyagi, 981-8555, Japan. kabe@niche.tohoku.ac.jp.
authors: Keietsu
authors: K
authors: Abe
keywords: Aspergillus oryzae; Fungal C6-type transcription factor; RiPS pathway; Secondary metabolite; Ustiloxin B