title: Activation of flavonoid biosynthesis by solar radiation in bilberry ( Vaccinium myrtillus L) leaves.
abstract: The effect of solar radiation on flavonoid biosynthesis was studied in bilberry ( Vaccinium myrtillus L.) leaves. Expression of flavonoid pathway genes of bilberry was studied in the upper leaves of bilberry, exposed to direct sunlight, in the shaded leaves growing lower in the same plants and in fruits. Bilberry-specific digoxigenin-dUTP-labeled cDNA fragments of five genes from the general phenylpropanoid pathway coding phenylalanine ammonia-lyase and from the flavonoid pathway coding chalcone synthase, flavanone 3-hydroxylase, dihydroflavonol 4-reductase, and anthocyanidin synthase were used as probes in gene expression analysis. Anthocyanins, catechins, proanthocyanidins, flavonols and hydroxycinnamic acids from the leaves and fruits were identified and quantified using high-performance liquid chromatography combined with a diode array detector. An increase in the expression of the studied flavonoid pathway genes was observed in leaves growing under direct sun exposure. Also, the concentrations of anthocyanins, catechins, flavonols and hydroxycinnamic acids were higher in the leaves exposed to direct sunlight. However, the concentration of polymeric procyanidins was lower in sun-exposed leaves, whereas that of prodelphinidins was slightly increased. The results give further support for the protective role of flavonoids and hydroxy cinnamic acids against high solar radiation in plants. Also, the roles of different flavonoid compounds as a defense against stress caused by sun exposure is discussed.
authors.affiliation: Department of Biology/Botany, University of Oulu, POB 3000, 90014, Oulu, Finland. laura.jaakola@oulu.fi
authors.forename: Laura
authors.initials: L
authors.lastname: Jaakola
authors.forename: Kaisu
authors.initials: K
authors.lastname: Määttä-Riihinen
authors.forename: Sirpa
authors.initials: S
authors.lastname: Kärenlampi
authors.forename: Anja
authors.initials: A
authors.lastname: Hohtola
mesh_terms: D000064:Acclimatization / Q000502:physiology / Q000528:radiation effects; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D005419:Flavonoids / Q000096:biosynthesis* / Q000528:radiation effects; D005638:Fruit / Q000378:metabolism / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D013472:Sunlight; D029800:Vaccinium myrtillus / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D005419:Flavonoids; D006899:Mixed Function Oxygenases; D000429:Alcohol Oxidoreductases; C056570:dihydroflavanol 4-reductase; D010105:Oxygenases; C048797:flavanone 3-dioxygenase; C118159:anthocyanidin synthase; D000217:Acyltransferases; C020141:flavanone synthetase; D010650:Phenylalanine Ammonia-Lyase