title: Molecular characterization of the oxalate oxidase involved in the response of barley to the powdery mildew fungus.
abstract: Previously we reported that oxalate oxidase activity increases in extracts of barley (Hordeum vulgare) leaves in response to the powdery mildew fungus (Blumeria [syn. Erysiphe] graminis f.sp. hordei) and proposed this as a source of H2O2 during plant-pathogen interactions. In this paper we show that the N terminus of the major pathogen-response oxalate oxidase has a high degree of sequence identity to previously characterized germin-like oxalate oxidases. Two cDNAs were isolated, pHvOxOa, which represents this major enzyme, and pHvOxOb', representing a closely related enzyme. Our data suggest the presence of only two oxalate oxidase genes in the barley genome, i.e. a gene encoding HvOxOa, which possibly exists in several copies, and a single-copy gene encoding HvOxOb. The use of 3' end gene-specific probes has allowed us to demonstrate that the HvOxOa transcript accumulates to 6 times the level of the HvOxOb transcript in response to the powdery mildew fungus. The transcripts were detected in both compatible and incompatible interactions with a similar accumulation pattern. The oxalate oxidase is found exclusively in the leaf mesophyll, where it is cell wall located. A model for a signal transduction pathway in which oxalate oxidase plays a central role is proposed for the regulation of the hypersensitive response.
authors.affiliation: Plant Pathology Section, Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
authors.forename: F
authors.initials: F
authors.lastname: Zhou
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: P L
authors.initials: PL
authors.lastname: Gregersen
authors.forename: J D
authors.initials: JD
authors.lastname: Mikkelsen
authors.forename: E
authors.initials: E
authors.lastname: de Neergaard
authors.forename: D B
authors.initials: DB
authors.lastname: Collinge
authors.forename: H
authors.initials: H
authors.lastname: Thordal-Christensen
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017343:Genes, Plant; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics* / Q000382:microbiology; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D007527:Isoenzymes; D010940:Plant Proteins; D010088:Oxidoreductases; C020598:oxalate oxidase