The Roles of a Flavone-6-Hydroxylase and 7-O-Demethylation in the Flavone Biosynthetic Network of Sweet Basil

Berim, Anna; Gang, David R.

doi:10.1074/jbc.m112.420448

Cited by 49 publications

(57 citation statements)

References 60 publications

(70 reference statements)

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“…Furthermore, reinforcement of biosynthetic route to methoxylated flavonoids is thus given here with the tentative identification of compounds from the flavanone to flavone pathway. [22,23] In view that the genus Plectranthus, and specifically species P. amboinicus, has seen limited study by ESI MS/MS characterization, the results presented here expand the knowledge base and the characterization of the genus. [1,3] A key finding is the confirmation of the tendency for the genus Plectranthus to form conjugates.…”

Section: Discussionmentioning

confidence: 89%

“…Berim and Gang describe a biosynthetic route from methoxyflavanones to methoxyflavones. [22] Compound IV, however, does not exhibit the elimination of methoxy moiety in its mass spectrum. The sequence 329, 314, 299, and 281 indicates the elimination of two methyl groups followed by a dehydration step in the fragmentation sequence.…”

Section: Hplc Esi Ms Msmentioning

confidence: 97%

“…[9][10][11][12][13] A study of biosynthetic pathway to polymethoxy flavones from Lamiaceae species suggests that methylation at C-7 is a needed substrate structural feature for the enzyme system that catalyzes hydroxylation at C-6. [22] Furthermore, the study revealed that hydroxylation of the C-5 position of the flavone ring structure is also a necessity at the active site of the enzyme. It is therefore proposed that compound III which is isomeric to cirsimaritin, 4 0 5-dihydroxy-6,7-dimethoxyflavone, is ladanein, 5,6-dihydroxy-4 0 ,7-dimethoxyflavone.…”

Section: Hplc Esi Ms Msmentioning

confidence: 99%

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The application of HPLC ESI MS in the investigation of the flavonoids and flavonoid glycosides of a Caribbean Lamiaceae plant with potential for bioaccumulation

Peter

Peru

Fahlman

et al. 2015

Journal of Environmental Science and Health, Part B

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As part of an exchange technology program between the government of Barbados and Environment Canada, methanolic and aqueous extracts from the flavonoid-rich Lamiaceae family were characterized using negative-ion electrospray mass spectrometry. The species investigated is part of the Caribbean Pharmacopoeia, and is used for a variety of health issues, including colds, flu, diabetes, and hypertension. The extracts were investigated for structural elucidation of phenolics, identification of chemical taxonomic profile, and evidence of bio-accumulator potential. The methanolic and aqueous leaf extracts of Plectranthus amboinicus yielded rosmarinic acid, ladanein, cirsimaritin, and other methoxylated flavonoids. This genus also shows a tendency to form conjugates with monosaccharides, including glucose, galactose, and rhamnose. The aqueous extract yielded four isomeric rhamnosides. The formation of conjugates by Plectranthus amboinicus is thus evidence of high bioaccumulator significance.

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Section: Discussionmentioning

confidence: 89%

Section: Hplc Esi Ms Msmentioning

confidence: 97%

Section: Hplc Esi Ms Msmentioning

confidence: 99%

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The application of HPLC ESI MS in the investigation of the flavonoids and flavonoid glycosides of a Caribbean Lamiaceae plant with potential for bioaccumulation

Peter

Peru

Fahlman

et al. 2015

Journal of Environmental Science and Health, Part B

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“…Other P450s acting in flavonoid biosynthetic pathways include 2-hydroxyisoflavanone synthase (commonly known as isoflavone synthase, CYP93Cs) (Akashi et al 1999a;Jung et al 2000), isoflavone 2 0 -hydroxylase (CYP81E1) (Akashi et al 1998a), and flavone 6-hydroxylase (CYP82D33, D62) (Berim and Gang 2013). However, they are not involved in floral pigment biosynthesis or have not been used to modify flower color.…”

Section: Flavone Biosynthesismentioning

confidence: 98%

Metabolic Engineering of Flower Color Pathways Using Cytochromes P450

Tanaka

Brugliera

2014

Fifty Years of Cytochrome P450 Research

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A single plant species can contain more than 250 cytochromes P450. Cytochromes P450 catalyze various reactions in plant biosynthetic pathways and play critical and diversified roles in the biosynthesis of primary and specialized (secondary) compounds, including flavonoids. Flavonoids and their colored derivatives, anthocyanins, are major constituents of flower color. Functional combinations of the cytochromes P450, flavonoid 3, and flavone synthase II (FNSII, CYP93B) determine flavonoid structure and flower color. The number of hydroxyl groups on the B-ring of anthocyanins catalyzed by F3 0 H and F3 0 5 0 H have an impact on the color: the more the bluer. Wild-type or traditionally bred carnations, roses, and chrysanthemums lack blue/violet flower colors because of the deficiency of a F3 0 5 0 H and therefore lack the trihydroxylated (B-ring) anthocyanins based upon delphinidin. Metabolic engineering of the anthocyanin pathway and specifically manipulation of F3 0 5 0 H and F3 0 H genes has produced an array of flower color modifications in many species. By optimizing transgene expression and suppressing endogenous genes in a species-specific manner, transgenic carnations, roses, and chrysanthemums producing novel violet/blue-hued flowers were engineered. Downregulation of F3 0 5 0 H and F3 0 H genes, often with expression of a dihydroflavonol 4-reductase gene, yielded redder flowers in petunia, tobacco, and torenia. Modulation of FNSII gene expression also impacts flower color as flavones act as co-pigments to induce bluing of anthocyanins and flavones and anthocyanins also share the same precursors.

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“…Similar or identical methoxylated flavonoids are common in the mint family, but are also found scattered in various families across the plant kingdom (Wollenweber, ). Flavonoid 6‐hydroxylation has been clarified in three species, and found to be catalyzed by non‐homologous proteins in all three instances (Latunde‐Dada et al ., ; Anzellotti and Ibrahim, ; Berim and Gang, ), exemplifying the frequency of convergent evolution in plant specialized metabolism (Pichersky and Lewinsohn, ). The enzymatic flavonoid 8‐hydroxylation has only been detected in crude protein extracts from the petals of Chrysanthemum segetum (Asteraceae) (Halbwirth and Stich, ).…”

Section: Introductionmentioning

confidence: 99%

Unexpected roles for ancient proteins: flavone 8‐hydroxylase in sweet basil trichomes is a Rieske‐type, PAO‐family oxygenase

2014

Self Cite

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SUMMARYMost elucidated hydroxylations in plant secondary metabolism are catalyzed by oxoglutarate-or cytochrome P450-dependent oxygenases. Numerous hydroxylations still evade clarification, suggesting that they might be performed by alternative enzyme types. Here, we report the identification of the flavone 8-hydroxylase (F8H) in sweet basil (Ocimum basilicum L.) trichomes as a Rieske-type oxygenase. Several features of the F8H activity in trichome protein extracts helped to differentiate it from a cytochrome P450-catalyzed reaction and identify candidate genes in the basil trichome EST database. The encoded ObF8H proteins share approximately 50% identity with Rieske-type protochlorophyllide a oxygenases (PTC52) from higher plants. Homology cloning and DNA blotting revealed the presence of several PTC52-like genes in the basil genome. The transcripts of the candidate gene designated ObF8H-1 are strongly enriched in trichomes compared to whole young leaves, indicating trichome-specific expression. The full-length ObF8H-1 protein possesses a predicted N-terminal transit peptide, which directs green fluorescent protein at least in part to chloroplasts. The F8H activity in crude trichome protein extracts correlates well with the abundance of ObF8H peptides. The purified recombinant ObF8H-1 displays high affinity for salvigenin and is inactive with other tested flavones except cirsimaritin, which is 8-hydroxylated with less than 0.2% relative activity. The efficiency of in vivo 8-hydroxylation by engineered yeast was improved by manipulation of protein subcellular targeting. BLAST searches showed that occurrence of several PTC52-like genes is rather common in sequenced plant genomes. The discovery of ObF8H suggests that Rieske-type oxygenases may represent overlooked candidate catalysts for oxygenations in specialized plant metabolism.

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The Roles of a Flavone-6-Hydroxylase and 7-O-Demethylation in the Flavone Biosynthetic Network of Sweet Basil

Cited by 49 publications

References 60 publications

The application of HPLC ESI MS in the investigation of the flavonoids and flavonoid glycosides of a Caribbean Lamiaceae plant with potential for bioaccumulation

The application of HPLC ESI MS in the investigation of the flavonoids and flavonoid glycosides of a Caribbean Lamiaceae plant with potential for bioaccumulation

Metabolic Engineering of Flower Color Pathways Using Cytochromes P450

Unexpected roles for ancient proteins: flavone 8‐hydroxylase in sweet basil trichomes is a Rieske‐type, PAO‐family oxygenase

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