title: Temperature and nitrogen effects on regulators and products of the flavonoid pathway: experimental and kinetic model studies.
abstract: The flavonoid pathway is known to be up-regulated by different environmental stress factors. Down-regulation of the pathway is much less studied and is emphasized in the present work. Flavonoid accumulation was induced by exposing plants for 1 week to nitrogen depletion at 10 degrees C, giving high levels of anthocyanins and 3-glucoside-7-rhamnosides, 3,7-di-rhamnosides and 3-rutinoside-7-rhamnosides of kaempferol and quercetin. Flavonol accumulation as influenced by temperatures and nitrogen supply was not related to the glycosylation patterns but to the classification as quercetin and kaempferol. When nitrogen was re-supplied, transcripts for main regulators of the pathway, PAP1/GL3 and PAP2/MYB12, fell to less than 1 and 0.1% of initial values, respectively, during 24 h in the 15-30 degrees C temperature range. Anthocyanins showed a half-life of approximately 1 d, while the degradation of flavonols was much slower. Interestingly, the initial fluxes of anthocyanin and flavonol degradations were found to be temperature-independent. A kinetic model for the flavonoid pathway was constructed. In order to get the observed concentration-temperature profiles as well as the temperature compensation in the flavonoid degradation flux, the model predicts that the flavonoid pathway shows an increased temperature sensitivity at the end of the pathway, where the up-regulation by PAP/GL3 has been found to be largest.
authors.affiliation: University of Stavanger, Centre for Organelle Research, Faculty of Science and Technology, Stavanger, Norway.
authors.forename: Kristine M
authors.initials: KM
authors.lastname: Olsen
authors.forename: Rune
authors.initials: R
authors.lastname: Slimestad
authors.forename: Unni S
authors.initials: US
authors.lastname: Lea
authors.forename: Cato
authors.initials: C
authors.lastname: Brede
authors.forename: Trond
authors.initials: T
authors.lastname: Løvdal
authors.forename: Peter
authors.initials: P
authors.lastname: Ruoff
authors.forename: Michel
authors.initials: M
authors.lastname: Verheul
authors.forename: Cathrine
authors.initials: C
authors.lastname: Lillo
mesh_terms: D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D005419:Flavonoids / Q000096:biosynthesis*; D044948:Flavonols / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D044949:Kaempferols / Q000096:biosynthesis; D007700:Kinetics; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D000073718:Pancreatitis-Associated Proteins; D011794:Quercetin / Q000096:biosynthesis; D018749:RNA, Plant / Q000378:metabolism; D013696:Temperature
chemical_list: D000872:Anthocyanins; D005419:Flavonoids; D044948:Flavonols; D044949:Kaempferols; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D018749:RNA, Plant; C006552:kaempferol; D011794:Quercetin; D009584:Nitrogen