title: Expression of Biphenyl Synthase Genes and Formation of Phytoalexin Compounds in Three Fire Blight-Infected Pyrus communis Cultivars.
abstract: Pear (Pyrus communis) is an economically important fruit crop. Drops in yield and even losses of whole plantations are caused by diseases, most importantly fire blight which is triggered by the bacterial pathogen Erwinia amylovora. In response to the infection, biphenyls and dibenzofurans are formed as phytoalexins, biosynthesis of which is initiated by biphenyl synthase (BIS). Two PcBIS transcripts were cloned from fire blight-infected leaves and the encoded enzymes were characterized regarding substrate specificities and kinetic parameters. Expression of PcBIS1 and PcBIS2 was studied in three pear cultivars after inoculation with E. amylovora. Both PcBIS1 and PcBIS2 were expressed in 'Harrow Sweet', while only PcBIS2 transcripts were detected in 'Alexander Lucas' and 'Conference'. Expression of the PcBIS genes was observed in both leaves and the transition zone of the stem; however, biphenyls and dibenzofurans were only detected in stems. The maximum phytoalexin level (~110 μg/g dry weight) was observed in the transition zone of 'Harrow Sweet', whereas the concentrations were ten times lower in 'Conference' and not even detectable in 'Alexander Lucas'. In 'Harrow Sweet', the accumulation of the maximum phytoalexin level correlated with the halt of migration of the transition zone, whereby the residual part of the shoot survived. In contrast, the transition zones of 'Alexander Lucas' and 'Conference' advanced down to the rootstock, resulting in necrosis of the entire shoots.
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Chizzali
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.
authors.forename: Asya K
authors.initials: AK
authors.lastname: Swiddan
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.
authors.forename: Sahar
authors.initials: S
authors.lastname: Abdelaziz
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.
authors.forename: Mariam
authors.initials: M
authors.lastname: Gaid
authors.affiliation: Julius Kühn Institute, Federal Research Centre for Cultivated Plants, Institute for Resistance Research and Stress Tolerance, Erwin-Baur-Str. 27, 06484, Quedlinburg, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Richter
authors.affiliation: Biotechnology of Natural Products, Life Science Center Weihenstephan, Technische Universität München, Liesel-Beckmann-Str. 1, 85354, Freising, Germany.
authors.forename: Thilo C
authors.initials: TC
authors.lastname: Fischer
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.
authors.forename: Benye
authors.initials: B
authors.lastname: Liu
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.
authors.forename: Ludger
authors.initials: L
authors.lastname: Beerhues
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry; D003001:Cloning, Molecular; D000072318:Dibenzofurans / Q000737:chemistry; D044084:Erwinia amylovora / Q000254:growth & development*; D010935:Plant Diseases / Q000382:microbiology* / Q000517:prevention & control*; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism / Q000382:microbiology; D048630:Polyketide Synthases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D031989:Pyrus / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism*; D000094162:Phytoalexins
chemical_list: D001713:Biphenyl Compounds; D000072318:Dibenzofurans; D010940:Plant Proteins; D048630:Polyketide Synthases; D012717:Sesquiterpenes; D000094162:Phytoalexins; C010574:biphenyl