Characterization of two candidate flavone 8-O-methyltransferases suggests the existence of two potential routes to nevadensin in sweet basil

Berim, Anna; Gang, David R.

doi:10.1016/j.phytochem.2013.05.001

Cited by 24 publications

(33 citation statements)

References 26 publications

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“…To investigate the genes responsible for the biosynthesis of wogonin, we screened the gene models annotated as OMTs from the S. baicalensis genome sequence, then performed BLAST searches against the database using sweet basil 8-OMT sequences as baits (Berim and Gang, 2013). This returned six genes encoding type II OMTs ( Supplemental Table 16), which were closely related to the PFOMT (phenylpropanoid and flavonoid OMT) gene family, so we named them SbPFOMTs.…”

Section: Identification Of Genes Encoding O-methyltransferases With Pmentioning

confidence: 99%

The Reference Genome Sequence of Scutellaria baicalensis Provides Insights into the Evolution of Wogonin Biosynthesis

et al. 2019

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Scutellaria baicalensis Georgi is important in Chinese traditional medicine where preparations of dried roots, ''Huang Qin,'' are used for liver and lung complaints and as complementary cancer treatments. We report a high-quality reference genome sequence for S. baicalensis where 93% of the 408.14-Mb genome has been assembled into nine pseudochromosomes with a super-N50 of 33.2 Mb. Comparison of this sequence with those of closely related species in the order Lamiales, Sesamum indicum and Salvia splendens, revealed that a specialized metabolic pathway for the synthesis of 4 0 -deoxyflavone bioactives evolved in the genus Scutellaria. We found that the gene encoding a specific cinnamate coenzyme A ligase likely obtained its new function following recent mutations, and that four genes encoding enzymes in the 4 0 -deoxyflavone pathway are present as tandem repeats in the genome of S. baicalensis. Further analyses revealed that gene duplications, segmental duplication, gene amplification, and point mutations coupled to gene neo-and subfunctionalizations were involved in the evolution of 4 0 -deoxyflavone synthesis in the genus Scutellaria. Our study not only provides significant insight into the evolution of specific flavone biosynthetic pathways in the mint family, Lamiaceae, but also will facilitate the development of tools for enhancing bioactive productivity by metabolic engineering in microbes or by molecular breeding in plants. The reference genome of S. baicalensis is also useful for improving the genome assemblies for other members of the mint family and offers an important foundation for decoding the synthetic pathways of bioactive compounds in medicinal plants.

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Section: Identification Of Genes Encoding O-methyltransferases With Pmentioning

confidence: 99%

The Reference Genome Sequence of Scutellaria baicalensis Provides Insights into the Evolution of Wogonin Biosynthesis

et al. 2019

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“…The relative proportion of 8‐substituted flavones is ca. 40–60% in all lines (Berim and Gang, ). Accordingly, it was reasonable to expect ESTs from all basil lines to be represented in promising candidate contigs.…”

Section: Resultsmentioning

confidence: 97%

“…The strongly varying F8H activities (Figure ) are in contrast with the relative abundances of 8‐oxygenated flavones, which are similar in all four basil lines (Berim et al ., ; Berim and Gang, ). One of the factors that could contribute to this discrepancy is the spatial separation of salvigenin, which is produced in the cytosol, and ObF8H proteins, which are likely to be active in plastids.…”

Section: Resultsmentioning

confidence: 99%

“…With the functional 8‐oxygenation, the cells lines designated ‘8HS’ would be expected to accumulate 8‐hydroxysalvigenin. The strains based on the parent strain designated ‘GB’, which additionally expressed the basil flavone 8‐ O ‐methyltransferase, ObF8OMT‐1 (Berim and Gang, ), were expected to yield gardenin B as the major 8‐substituted flavone. In addition to ObF8H‐1, non‐photosynthetic basil Fdx and FNR were introduced into all cell strains to provide the necessary electron transfer capacity.…”

Section: Resultsmentioning

confidence: 99%

“…Relevant steps of the flavone metabolic network in basil. Enzyme designations (Ob FOMT 1‐5, CYP 82D33, ObF8 OMT ‐1) are as published originally (Berim et al ., ; Berim and Gang, ,b). 7‐ O ‐Demethylase activity was demonstrated earlier (Berim and Gang, ).…”

Section: Introductionmentioning

confidence: 99%

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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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Harnessing Plant Trichome Biochemistry for the Production of Useful Compounds

Tissier

2018

Molecular Pharming

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Characterization of two candidate flavone 8-O-methyltransferases suggests the existence of two potential routes to nevadensin in sweet basil

Cited by 24 publications

References 26 publications

The Reference Genome Sequence of Scutellaria baicalensis Provides Insights into the Evolution of Wogonin Biosynthesis

The Reference Genome Sequence of Scutellaria baicalensis Provides Insights into the Evolution of Wogonin Biosynthesis

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

Harnessing Plant Trichome Biochemistry for the Production of Useful Compounds

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