title: Formation of biphenyl and dibenzofuran phytoalexins in the transition zones of fire blight-infected stems of Malus domestica cv. 'Holsteiner Cox' and Pyrus communis cv. 'Conference'.
abstract: In the rosaceous subtribe Pyrinae (formerly subfamily Maloideae), pathogen attack leads to formation of biphenyls and dibenzofurans. Accumulation of these phytoalexins was studied in greenhouse-grown grafted shoots of Malus domestica cv. 'Holsteiner Cox' and Pyrus communis cv. 'Conference' after inoculation with the fire blight bacterium, Erwinia amylovora. No phytoalexins were found in leaves. However, both classes of defence compounds were detected in the transition zone of stems. The flanking stem segments above and below this zone, which were necrotic and healthy, respectively, were devoid of detectable phytoalexins. The transition zone of apple stems contained the biphenyls 3-hydroxy-5-methoxyaucuparin, aucuparin, noraucuparin and 2'-hydroxyaucuparin and the dibenzofurans eriobofuran and noreriobofuran. In pear, aucuparin, 2'-hydroxyaucuparin, noreriobofuran and in addition 3,4,5-trimethoxybiphenyl were detected. The total phytoalexin content in the transition zone of pear was 25 times lower than that in apple. Leaves and stems of mock-inoculated apple and pear shoots lacked phytoalexins. A number of biphenyls and dibenzofurans were tested for their in vitro antibacterial activity against some Erwinia amylovora strains. The most efficient compound was 3,5-dihydroxybiphenyl (MIC=115 μg/ml), the immediate product of biphenyl synthase which initiates phytoalexin biosynthesis.
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106 Braunschweig, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Chizzali
authors.forename: Mohammed N A
authors.initials: MN
authors.lastname: Khalil
authors.forename: Till
authors.initials: T
authors.lastname: Beuerle
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schuehly
authors.forename: Klaus
authors.initials: K
authors.lastname: Richter
authors.forename: Henryk
authors.initials: H
authors.lastname: Flachowsky
authors.forename: Andreas
authors.initials: A
authors.lastname: Peil
authors.forename: Magda-Viola
authors.initials: MV
authors.lastname: Hanke
authors.forename: Benye
authors.initials: B
authors.lastname: Liu
authors.forename: Ludger
authors.initials: L
authors.lastname: Beerhues
mesh_terms: D001572:Benzofurans / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D044084:Erwinia amylovora / Q000187:drug effects / Q000276:immunology; D027845:Malus / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D010935:Plant Diseases / Q000382:microbiology*; D057865:Plant Immunity; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D031989:Pyrus / Q000378:metabolism* / Q000382:microbiology; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000094162:Phytoalexins
chemical_list: D001572:Benzofurans; D012717:Sesquiterpenes; C023614:dibenzofuran; D000094162:Phytoalexins