Polyketide derivatives active against Botrytis cinerea in Gerbera hybrida.
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.
Koskela
Satu
S
Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
Söderholm
Päivi P
PP
Ainasoja
Miia
M
Wennberg
Tero
T
Klika
Karel D
KD
Ovcharenko
Vladimir V
VV
Kylänlahti
Irene
I
Auerma
Tiina
T
Yli-Kauhaluoma
Jari
J
Pihlaja
Kalevi
K
Vuorela
Pia M
PM
Teeri
Teemu H
TH
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
D000935:Antifungal Agents; D018942:Macrolides; D010936:Plant Extracts; D048630:Polyketide Synthases