title: Polyketide derivatives active against Botrytis cinerea in Gerbera hybrida.
abstract: A previously isolated cDNA molecule from Gerbera hybrida (Asteraceae) codes for a new chalcone synthase-like polyketide synthase, 2-pyrone synthase (2PS). 2PS is able to synthesise 4-hydroxy-6-methyl-2-pyrone (triacetolactone), a putative precursor for gerberin and parasorboside, two abundant glucosides in gerbera. In this study, we show that gerbera plants transformed with the gene for 2PS in an antisense orientation and unable to synthesise gerberin and parasorboside are susceptible to Botrytis cinerea infection. In addition to the preformed glucosides, the transgenic plants also lack several compounds that are induced in control plants when infected with the mould. Some of these induced substances are effective in inhibiting fungal growth both in vitro and in vivo. Two of the phytoalexins were identified as the aglycones of gerberin and trans-parasorboside. The third phytoalexin is a rare coumarin, 4-hydroxy-5-methylcoumarin; however, it is typical of many plants of the sunflower family Asteraceae. The coumarin cannot be structurally derived from either gerberin or parasorboside, but may be derived from a related polyketide intermediate.
authors.affiliation: Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
authors.forename: Satu
authors.initials: S
authors.lastname: Koskela
authors.forename: Päivi P
authors.initials: PP
authors.lastname: Söderholm
authors.forename: Miia
authors.initials: M
authors.lastname: Ainasoja
authors.forename: Tero
authors.initials: T
authors.lastname: Wennberg
authors.forename: Karel D
authors.initials: KD
authors.lastname: Klika
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Ovcharenko
authors.forename: Irene
authors.initials: I
authors.lastname: Kylänlahti
authors.forename: Tiina
authors.initials: T
authors.lastname: Auerma
authors.forename: Jari
authors.initials: J
authors.lastname: Yli-Kauhaluoma
authors.forename: Kalevi
authors.initials: K
authors.lastname: Pihlaja
authors.forename: Pia M
authors.initials: PM
authors.lastname: Vuorela
authors.forename: Teemu H
authors.initials: TH
authors.lastname: Teeri
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D019659:Asteraceae / Q000187:drug effects* / Q000235:genetics / Q000382:microbiology*; D001681:Biological Assay; D020171:Botrytis / Q000187:drug effects*; D002855:Chromatography, Thin Layer; D018942:Macrolides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010935:Plant Diseases / Q000382:microbiology; D010936:Plant Extracts / Q000494:pharmacology; D030821:Plants, Genetically Modified; D048630:Polyketide Synthases / Q000378:metabolism; D014170:Transformation, Genetic / Q000187:drug effects
chemical_list: D000935:Antifungal Agents; D018942:Macrolides; D010936:Plant Extracts; D048630:Polyketide Synthases