title: Premature and ectopic anthocyanin formation by silencing of anthocyanidin reductase in strawberry (Fragaria × ananassa).
abstract: Strawberry (Fragaria × ananassa) is a fruit crop with a distinct biphasic flavonoid biosynthesis. Whereas, in the immature receptacle, high levels of proanthocyanidins accumulate, which are associated with herbivore deterrence and pathogen defense, the prominent color-giving anthocyanins are primarily produced in ripe 'fruits' helping to attract herbivores for seed dispersal. Here, constitutive experimental down-regulation of one branch of proanthocyanidin biosynthesis was performed. As a result, the proportion of epicatechin monomeric units within the proanthocyanidin polymer chains was reduced, but this was not the case for the epicatechin starter unit. Shortened chain lengths of proanthocyanidins were also observed. All enzymatic activities for the production of color-giving anthocyanins were already present in unripe fruits at levels allowing a striking red anthocyanin phenotype in unripe fruits of the RNAi silencing lines. An immediately recognizable phenotype was also observed for the stigmata of flowers, which is another epicatechin-forming tissue. Thus, the down-regulation of anthocyanidin reductase (ANR) induced a redirection of the proanthocyanidin pathway, leading to premature and ectopic anthocyanin biosynthesis via enzymatic glycosylation as the alternative pathway. This redirection is also seen in flavonol biosynthesis, which is paralleled by higher pollen viability in silencing lines. ANRi transgenic lines of strawberry provide a versatile tool for the study of the biological functions of proanthocyanidins.
authors.affiliation: Plant Biochemistry and Physiology, Ludwig-Maximilians-University Munich, Großhadernerstr 2-4, D-82152, Planegg-Martinsried, Germany.
authors.forename: Thilo C
authors.initials: TC
authors.lastname: Fischer
authors.affiliation: Plant Biochemistry and Physiology, Ludwig-Maximilians-University Munich, Großhadernerstr 2-4, D-82152, Planegg-Martinsried, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Mirbeth
authors.affiliation: Julius Kühn-Institute - Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Horticultural and Fruit Crops, Pillnitzer Platz 3a, 01326 Pillnitz, Dresden, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Rentsch
authors.affiliation: Biotechnology of Natural Products, Technical University Munich (TUM), Liesel-Beckmann-Str 1, D-85354, Freising, Germany.
authors.forename: Corina
authors.initials: C
authors.lastname: Sutter
authors.affiliation: Biotechnology of Natural Products, Technical University Munich (TUM), Liesel-Beckmann-Str 1, D-85354, Freising, Germany.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Ring
authors.affiliation: Julius Kühn-Institute - Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Horticultural and Fruit Crops, Pillnitzer Platz 3a, 01326 Pillnitz, Dresden, Germany.
authors.forename: Henryk
authors.initials: H
authors.lastname: Flachowsky
authors.affiliation: Biotechnology of Natural Products, Technical University Munich (TUM), Liesel-Beckmann-Str 1, D-85354, Freising, Germany.
authors.forename: Ruth
authors.initials: R
authors.lastname: Habegger
authors.affiliation: Biotechnology of Natural Products, Technical University Munich (TUM), Liesel-Beckmann-Str 1, D-85354, Freising, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoffmann
authors.affiliation: Julius Kühn-Institute - Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Horticultural and Fruit Crops, Pillnitzer Platz 3a, 01326 Pillnitz, Dresden, Germany.
authors.forename: Magda-Viola
authors.initials: MV
authors.lastname: Hanke
authors.affiliation: Biotechnology of Natural Products, Technical University Munich (TUM), Liesel-Beckmann-Str 1, D-85354, Freising, Germany.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Schwab
mesh_terms: D015536:Down-Regulation; D005419:Flavonoids / Q000096:biosynthesis; D031985:Fragaria / Q000235:genetics / Q000378:metabolism*; D005638:Fruit / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011058:Pollen / Q000235:genetics / Q000502:physiology; D044945:Proanthocyanidins / Q000096:biosynthesis*
chemical_list: D005419:Flavonoids; D010940:Plant Proteins; D044945:Proanthocyanidins; D010088:Oxidoreductases
keywords: RNAi; anthocyanidin reductase (ANR); anthocyanin; epicatechin; flavonols; proanthocyanidins; strawberry (Fragaria × ananassa)