title: Transgenic rice seed expressing flavonoid biosynthetic genes accumulate glycosylated and/or acylated flavonoids in protein bodies.
abstract: Plant-specialized (or secondary) metabolites represent an important source of high-value chemicals. In order to generate a new production platform for these metabolites, an attempt was made to produce flavonoids in rice seeds. Metabolome analysis of these transgenic rice seeds using liquid chromatography-photodiode array-quadrupole time-of-flight mass spectrometry was performed. A total of 4392 peaks were detected in both transgenic and non-transgenic rice, 20-40% of which were only detected in transgenic rice. Among these, 82 flavonoids, including 37 flavonols, 11 isoflavones, and 34 flavones, were chemically assigned. Most of the flavonols and isoflavones were O-glycosylated, while many flavones were O-glycosylated and/or C-glycosylated. Several flavonoids were acylated with malonyl, feruloyl, acetyl, and coumaroyl groups. These glycosylated/acylated flavonoids are thought to have been biosynthesized by endogenous rice enzymes using newly synthesized flavonoids whose biosynthesis was catalysed by exogenous enzymes. The subcellular localization of the flavonoids differed depending on the class of aglycone and the glycosylation/acylation pattern. Therefore, flavonoids with the intended aglycones were efficiently produced in rice seeds via the exogenous enzymes introduced, while the flavonoids were variously glycosylated/acylated by endogenous enzymes. The results suggest that rice seeds are useful not only as a production platform for plant-specialized metabolites such as flavonoids but also as a tool for expanding the diversity of flavonoid structures, providing novel, physiologically active substances.
authors.affiliation: Transgenic Crop Research and Development Centre, National Institute of Agrobiological Sciences (NIAS), Tsukuba, Ibaraki, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ogo
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mori
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Nakabayashi
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Chuo-ku, Chiba 260-8675, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Saito
authors.affiliation: Transgenic Crop Research and Development Centre, National Institute of Agrobiological Sciences (NIAS), Tsukuba, Ibaraki, Japan takaiwa@affrc.go.jp.
authors.forename: Fumio
authors.initials: F
authors.lastname: Takaiwa
mesh_terms: D000215:Acylation; D002853:Chromatography, Liquid; D005419:Flavonoids / Q000378:metabolism*; D006031:Glycosylation; D055442:Metabolome; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D005419:Flavonoids
keywords: Flavonoid; genetically modified plant; glycosylation; liquid chromatography-mass spectrometry; metabolome; rice; secondary metabolite.