Dynamic metabolic changes in seeds and seedlings of Brassica napus (oilseed rape) suppressing UGT84A9 reveal plasticity and molecular regulation of the phenylpropanoid pathway. (April 2016)

• Record Type: Journal Article
• Authors: Hettwer, Karina; Böttcher, Christoph; Frolov, Andrej; Mittasch, Juliane; Albert, Andreas; von Roepenack-Lahaye, Edda; Strack, Dieter; Milkowski, Carsten
• Is Part Of: Phytochemistry. Volume 124(2016:Apr.)
• Page Start: 46
• Page End: 57
• Publication Date: 2016-04
• Subjects: Brassica napus -- Brassicaceae -- Metabolite profiling -- Gene silencing -- Glucosyltransferase -- Phenylpropanoids -- Sinapic acid esters -- UV-B stress; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2016.01.014
• Languages: English
• ISSNs: 0031-9422

Abstract

Graphical abstract: Suppression of UGT84A9 in seeds of Brassica napus blocks the major sink pathway of sinapic acid via 1- O -sinapoylglucose (SinGlc) and affects the accumulation pattern of hydroxycinnamic acid, hydroxybenzoic acid and flavonoid conjugates in seeds and seedlings. The UV-B stress response is not impaired. Highlights: In seeds of Brassica napus suppression of UGT84A9 affects 65 metabolites. 4- O -glycosylation and β-oxidation are used to bypass accumulation of sinapic acid. The altered chemotype is maintained in young seedlings. The lack of sinapoylmalate has no effect on the UV-B stress response of seedlings. 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 ( UGT84A9 i) lines massive alterations became evident in late stages of seed development affecting the accumulation levels of 58 secondary and 7 primary metabolites. UGT84A9 i 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.