Feedback inhibition of the general phenylpropanoid and flavonol biosynthetic pathways upon a compromised flavonol-3-O-glycosylation.
J. Exp. Bot. 63, 2465-2478 (2012)
Flavonols, phenylalanine-derived secondary metabolites, have protective and regulatory functions in plants. In Arabidopsis thaliana, they are consecutively glycosylated at their 3-OH and 7-OH groups. UGT78D1 and UGT78D2 are the major flavonol 3-O-glycosyltransferases in Arabidopsis leaves. The ugt78d1 ugt78d2 double mutant, which was strongly compromised in the initial 3-O-glycosylation, showed a severe and specific repression of flavonol biosynthesis, retaining only one-third of the wild-type level. This metabolic phenotype was associated with a repressed transcription of several flavonol biosynthetic genes including the committed step chalcone synthase [(CHS) or TRANSPARENT TESTA 4 (TT4)]. Furthermore, the committed step of the upstream, general phenylpropanoid pathway, phenylalanine ammonia-lyase (PAL), was down-regulated in its enzyme activity and in the transcription of the flavonol-related PAL1 and PAL2. However, a complete blocking of flavonoid biosynthesis at CHS released PAL inhibition in a tt4 ugt78d1 ugt78d2 line. PAL activity was even enhanced in the flavonol synthase 1 mutant, which compromises the final formation of flavonol aglycones. The dependence of the PAL feedback inhibition on flavonols was confirmed by chemical complementation of tt4 ugt78d1 ugt78d2 using naringenin, a downstream flavonoid intermediate, which restored the PAL repression. Although aglycones were not analytically detectable, this study provides genetic evidence for a novel, flavonol-dependent feedback inhibition of the flavonol biosynthetic pathway and PAL. It was conditioned by the compromised flavonol-3-O-conjugation and a decrease in flavonol content, yet dependent on a residual, flavonol synthase 1 (FLS1)-related capacity to form flavonol aglycones. Thus, this regulation would not react to a reduced metabolic flux into flavonol biosynthesis, but it might prevent the accumulation of non-glycosylated, toxic flavonols.
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Artikel: Journalartikel
Dokumenttyp
Wissenschaftlicher Artikel
Typ der Hochschulschrift
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Schlagwörter
Feedback inhibition; flavonoids; flavonols; flavonol synthase; phenylalanine ammonia-lyase; phenylpropanoids; UDP-carbohydrate-dependent glycosyltransferase; PHENYLALANINE AMMONIA-LYASE; TRANSCRIPTOME COEXPRESSION ANALYSIS; TRANS-CINNAMIC ACID; ARABIDOPSIS-THALIANA; AUXIN TRANSPORT; DIFFERENTIAL EXPRESSION; FUNCTIONAL-ANALYSIS; PLANT-GROWTH; FACTOR HY5; ZEA-MAYS
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Sprache
Veröffentlichungsjahr
2012
Prepublished im Jahr
HGF-Berichtsjahr
2012
ISSN (print) / ISBN
0022-0957
e-ISSN
1460-2431
ISBN
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Konferenztitel
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Konferenzband
Quellenangaben
Band: 63,
Heft: 7,
Seiten: 2465-2478
Artikelnummer: ,
Supplement: ,
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Verlag
Oxford University Press
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0000-00-00
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Gutachter
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0000-00-00
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0000-00-00
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weitere Inhaber
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Begutachtungsstatus
Peer reviewed
POF Topic(s)
30202 - Environmental Health
30204 - Cell Programming and Repair
Forschungsfeld(er)
Environmental Sciences
Genetics and Epidemiology
PSP-Element(e)
G-504900-002
G-500500-001
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Erfassungsdatum
2012-06-06