title: Evidence for a Ustilago maydis steroid 5alpha-reductase by functional expression in Arabidopsis det2-1 mutants.
abstract: We have identified a gene (udh1) in the basidiomycete Ustilago maydis that is induced during the parasitic interaction with its host plant maize (Zea mays). udh1 encodes a protein with high similarity to mammalian and plant 5alpha-steroid reductases. Udh1 differs from those of known 5alpha-steroid reductases by six additional domains, partially predicted to be membrane-spanning. A fusion protein of Udh1 and the green fluorescent protein provided evidence for endoplasmic reticulum localization in U. maydis. The function of the Udh1 protein was demonstrated by complementing Arabidopsis det2-1 mutants, which display a dwarf phenotype due to a mutation in the 5alpha-steroid reductase encoding DET2 gene. det2-1 mutant plants expressing either the udh1 or the DET2 gene controlled by the cauliflower mosaic virus 35S promoter differed from wild-type Columbia plants by accelerated stem growth, flower and seed development and a reduction in size and number of rosette leaves. The accelerated growth phenotype of udh1 transgenic plants was stably inherited and was favored under reduced light conditions. Truncation of the N-terminal 70 amino acids of the Udh1 protein abolished the ability to restore growth in det2-1 plants. Our results demonstrate the existence of a 5alpha-steroid reductase encoding gene in fungi and suggest a common ancestor between fungal, plant, and mammalian proteins.
authors.affiliation: Institut für Genetik und Mikrobiologie der Universität München, Maria-Ward-Strasse 1a, D-80638 Munich, Germany. basse@mailer.uni-marburg.de
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Basse
authors.forename: Christine
authors.initials: C
authors.lastname: Kerschbamer
authors.forename: Markus
authors.initials: M
authors.lastname: Brustmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Altmann
authors.forename: Regine
authors.initials: R
authors.lastname: Kahmann
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D001483:Base Sequence; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D030821:Plants, Genetically Modified; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014588:Ustilago / Q000201:enzymology / Q000235:genetics*; D003313:Zea mays / Q000235:genetics / Q000382:microbiology
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase