title: Dynamic metabolic changes in seeds and seedlings of Brassica napus (oilseed rape) suppressing UGT84A9 reveal plasticity and molecular regulation of the phenylpropanoid pathway.
abstract: In Brassica napus, suppression of the key biosynthetic enzyme UDP-glucose:sinapic acid glucosyltransferase (UGT84A9) inhibits the biosynthesis of sinapine (sinapoylcholine), the major phenolic component of seeds. Based on the accumulation kinetics of a total of 158 compounds (110 secondary and 48 primary metabolites), we investigated how suppression of the major sink pathway of sinapic acid impacts the metabolome of developing seeds and seedlings. In UGT84A9-suppressing (UGT84A9i) lines massive alterations became evident in late stages of seed development affecting the accumulation levels of 58 secondary and 7 primary metabolites. UGT84A9i seeds were characterized by decreased amounts of various hydroxycinnamic acid (HCA) esters, and increased formation of sinapic and syringic acid glycosides. This indicates glycosylation and β-oxidation as metabolic detoxification strategies to bypass intracellular accumulation of sinapic acid. In addition, a net loss of sinapic acid upon UGT84A9 suppression may point to a feedback regulation of HCA biosynthesis. Surprisingly, suppression of UGT84A9 under control of the seed-specific NAPINC promoter was maintained in cotyledons during the first two weeks of seedling development and associated with a reduced and delayed transformation of sinapine into sinapoylmalate. The lack of sinapoylmalate did not interfere with plant fitness under UV-B stress. Increased UV-B radiation triggered the accumulation of quercetin conjugates whereas the sinapoylmalate level was not affected.
authors.affiliation: Department of Secondary Metabolism, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: Hettwer
authors.affiliation: Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany; Julius Kühn Institute, Federal Research Centre for Cultivated Plants, Institute for Ecological Chemistry, Plant Analysis and Stored Product Protection, Königin-Luise-Strasse 19, 14195 Berlin, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Böttcher
authors.affiliation: Department of Secondary Metabolism, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany.
authors.forename: Andrej
authors.initials: A
authors.lastname: Frolov
authors.affiliation: Department of Secondary Metabolism, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany; Martin-Luther-University Halle-Wittenberg, Interdisciplinary Center for Crop Plant Research (IZN), Hoher Weg 8, 06120 Halle (Saale), Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Mittasch
authors.affiliation: Research Unit Environmental Simulation, Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Albert
authors.affiliation: Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany.
authors.forename: Edda
authors.initials: E
authors.lastname: von Roepenack-Lahaye
authors.affiliation: Department of Secondary Metabolism, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Strack
authors.affiliation: Martin-Luther-University Halle-Wittenberg, Interdisciplinary Center for Crop Plant Research (IZN), Hoher Weg 8, 06120 Halle (Saale), Germany. Electronic address: carsten.milkowski@izn.uni-halle.de.
authors.forename: Carsten
authors.initials: C
authors.lastname: Milkowski
mesh_terms: D029688:Brassica napus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D002794:Choline / Q000031:analogs & derivatives / Q000378:metabolism / Q000528:radiation effects; D018548:Cotyledon / Q000378:metabolism; D003373:Coumaric Acids / Q000032:analysis / Q000378:metabolism / Q000528:radiation effects; D005964:Glucosyltransferases / Q000378:metabolism* / Q000528:radiation effects; D008293:Malates / Q000378:metabolism; D015394:Molecular Structure; D010666:Phenylpropionates / Q000378:metabolism; D036226:Seedlings / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: C079164:2-O-sinapoylmalate; D003373:Coumaric Acids; D008293:Malates; D010666:Phenylpropionates; C005685:sinapine; C073734:sinapinic acid; D005964:Glucosyltransferases; C420119:UDP-glucose sinapate glucosyltransferase, Brassica napus; D002794:Choline
keywords: Brassica napus; Brassicaceae; Gene silencing; Glucosyltransferase; Metabolite profiling; Phenylpropanoids; Sinapic acid esters; UV-B stress