title: Erwinia amylovora affects the phenylpropanoid-flavonoid pathway in mature leaves of Pyrus communis cv. Conférence.
abstract: Flavonoids, which are synthesized by the phenylpropanoid-flavonoid pathway, not only contribute to fruit colour and photoprotection, they also may provide antimicrobial and structural components during interaction with micro-organisms. A possible response of this pathway was assessed in both mature and immature leaves of shoots of 2-year-old pear trees cv. Conférence, which were inoculated with the gram-negative bacterium Erwinia amylovora strain SGB 225/12, were mock-inoculated or were left untreated. The phenylpropanoid-flavonoid pathway was analysed by histological studies, by gene expression using RT-qPCR and by HPLC analyses of the metabolites at different time intervals after infection. Transcription patterns of two key genes anthocyanidin reductase (ANR) and chalcone synthase (CHS) related to the phenylpropanoid-flavonoid pathway showed differences between control, mock-inoculated and E. amylovora-inoculated mature leaves, with the strongest reaction 48 h after inoculation. The impact of E. amylovora was also visualised in histological sections, and confirmed by HPLC, as epicatechin -which is produced via ANR- augmented 72 h after inoculation in infected leaf tissue. Besides the effect of treatments, ontogenesis-related differences were found as well. The increase of certain key genes, the rise in epicatechin and the visualisation in several histological sections in this study suggest a non-negligible impact on the phenylpropanoid-flavonoid pathway in Pyrus communis due to inoculation with E. amylovora. In this study, we propose a potential role of this pathway in defence mechanisms, providing a detailed analysis of the response of this system attributable to inoculation with E. amylovora.
authors.affiliation: Molecular and Physical Plant Physiology, Faculty of Sciences, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Vrancken
authors.forename: M
authors.initials: M
authors.lastname: Holtappels
authors.forename: H
authors.initials: H
authors.lastname: Schoofs
authors.forename: T
authors.initials: T
authors.lastname: Deckers
authors.forename: D
authors.initials: D
authors.lastname: Treutter
authors.forename: R
authors.initials: R
authors.lastname: Valcke
mesh_terms: D002851:Chromatography, High Pressure Liquid; D044084:Erwinia amylovora / Q000502:physiology*; D005419:Flavonoids / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism* / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D020005:Propanols / Q000378:metabolism*; D031989:Pyrus / Q000378:metabolism* / Q000382:microbiology*
chemical_list: D005419:Flavonoids; D020005:Propanols; C439395:1-phenylpropanol
keywords: ANR; ANS; CHS; DFR; Ea-inoculated; Epicatechin; Erwinia amylovora; Erwinia amylovora inoculated; F7GT; FHT; FLS; LAR1; Leaf ontogenesis; NA; Naturstoff reagent A; PAL; PBS; Pear; Phenylpropanoid–flavonoid pathway; Phosphate Buffered Saline; Plant defence; ROS; RT-qPCR; anthocyanidin reductase; anthocyanidin synthase; chalcone synthase; dihydroflavonol-4-reductase; flavanon 3β hydroxylase; flavonoid 7-O-glucosyltransferase; flavonol synthase; leucoanthocyanidin reductase 1; phenylalanine ammonium lyase; reactive oxygen species