Functional Expression of an Arabidopsis cDNA Clone Encoding a Flavonol 3′-O-Methyltransferase and Characterization of the Gene Product

Muzac, Ingrid; Wang, Jing; Anzellotti, Dominique; Zhang, Hong; Ibrahim, Ragai K.

doi:10.1006/abbi.1999.1681

Cited by 99 publications

(67 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is not clear whether the 39-O-methylation in chrysoeriol occurs before or after flavone formation. Interestingly, two Arabidopsis O-methyltransferases, AtOMT1 and CCoAOMT7, were both reported to show catalytic activity toward luteolin in vitro (Muzac et al, 2000;Wils et al, 2013). Hence, it is possible that luteolin is methylated to chrysoeriol by AtOMT1 or CCoAOMT7 in our CYP93G1 transgenic Arabidopsis plants.…”

Section: Discussionmentioning

confidence: 87%

Cytochrome P450 93G1 Is a Flavone Synthase II That Channels Flavanones to the Biosynthesis of Tricin O-Linked Conjugates in Rice

et al. 2014

View full text Add to dashboard Cite

Flavones are a major class of flavonoids with a wide range of physiological functions in plants. They are constitutively accumulated as C-glycosides and O-linked conjugates in vegetative tissues of grasses. It has long been presumed that the two structural modifications of flavones occur through independent metabolic routes. Previously, we reported that cytochrome P450 93G2 (CYP93G2) functions as a flavanone 2-hydroxylase (F2H) that provides 2-hydroxyflavanones for C-glycosylation in rice (Oryza sativa). Flavone C-glycosides are subsequently formed by dehydratase activity on 2-hydroxyflavanone C-glycosides. On the other hand, O-linked modifications were proposed to proceed after the flavone nucleus is generated. In this study, we demonstrate that CYP93G1, the closest homolog of CYP93G2 in rice, is a bona fide flavone synthase II (FNSII) that catalyzes the direct conversion of flavanones to flavones. In recombinant enzyme assays, CYP93G1 desaturated naringenin and eriodictyol to apigenin and luteolin, respectively. Consistently, transgenic expression of CYP93G1 in Arabidopsis (Arabidopsis thaliana) resulted in the accumulation of different flavone O-glycosides, which are not naturally present in cruciferous plants. Metabolite analysis of a rice CYP93G1 insertion mutant further demonstrated the preferential depletion of tricin O-linked flavanolignans and glycosides. By contrast, redirection of metabolic flow to the biosynthesis of flavone C-glycosides was observed. Our findings established that CYP93G1 is a key branch point enzyme channeling flavanones to the biosynthesis of tricin O-linked conjugates in rice. Functional diversification of F2H and FNSII in the cytochrome P450 CYP93G subfamily may represent a lineage-specific event leading to the prevalent cooccurrence of flavone C-and O-linked derivatives in grasses today.

show abstract

Section: Discussionmentioning

confidence: 87%

Cytochrome P450 93G1 Is a Flavone Synthase II That Channels Flavanones to the Biosynthesis of Tricin O-Linked Conjugates in Rice

et al. 2014

View full text Add to dashboard Cite

show abstract

“…This group of genes significantly overlapped with the group of genes related to the synthesis of secondary walls (Table 1) and to the group of genes whose expression was enhanced in 35S:NST1 plants in a previous study (Mitsuda et al, 2005). Analysis by quantitative RT-PCR confirmed that the expression of genes involved in the biosynthesis of secondary walls, namely, IRX3, IRX4, IRX5, IRX10, IRX12, At OMT1, and FRAGILE FIBER8 (FRA8) (Taylor et al, 1999(Taylor et al, , 2003Muzac et al, 2000;Jones et al, 2001;Brown et al, 2005;Sawa et al, 2005;Zhong et al, 2005), was indeed suppressed in nst1-1 nst3-1 plants ( Figure 4I). IRX3 and IRX5 encode cellulose synthase (Taylor et al, 1999(Taylor et al, , 2003, IRX4, IRX12, and At OMT1 are related to lignin biosynthesis (Muzac et al, 2000;Jones et al, 2001;Brown et al, 2005;Sawa et al, 2005), and FRA8 is considered to function in the biosynthesis of xylan (Zhong et al, 2005).…”

Section: Nst1 and Nst3 Regulate The Expression Of Genes Involved In Bmentioning

confidence: 79%

NAC Transcription Factors, NST1 and NST3, Are Key Regulators of the Formation of Secondary Walls in Woody Tissues ofArabidopsis

et al. 2007

View full text Add to dashboard Cite

Wood is formed by the successive addition of secondary xylem, which consists of cells with a conspicuously thickened secondary wall composed mainly of lignin and cellulose. Several genes involved in lignin and cellulose biosynthesis have been characterized, but the factors that regulate the formation of secondary walls in woody tissues remain to be identified. In this study, we show that plant-specific transcription factors, designated NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1) and NST3, are key regulators of the formation of secondary walls in woody tissues of Arabidopsis thaliana. In nst1-1 nst3-1 double knockout plants, the secondary wall thickenings in interfascicular fibers and secondary xylem, except for vascular vessels, were completely suppressed without affecting formation of cells destined to be woody tissues. Conversely, as shown previously for NST1, overexpression of NST3 induced ectopic secondary wall thickenings in various aboveground tissues. Furthermore, the expression of chimeric repressors derived from NST1 and NST3 suppressed secondary wall thickenings in the presumptive interfascicular fibers. Because putative orthologs of NST1 and NST3 are present in the genome of poplar, our results suggest that they are also key regulators of the formation of secondary walls in woody plants and could be used as a tool for the genetic engineering of wood and its derivatives.

show abstract

“…Their specificities, especially those of the new subcluster, overlap with class II OMTs. Recent studies described a multifunctional class II OMT from ripening Fragaria vesca as able to in vitro methylate volatiles as well as various catechol-like structures including caffeoylCoA (56), and a class II OMT capable of specifically methylating quercetin at the 3Ј-position (57). This in vitro functional redundancy of class I and II enzymes may be circumvented in vivo by a tightly controlled compartmentation and tissuespecific expression (11,13).…”

Section: Discussionmentioning

confidence: 99%

A Novel Mg2+-dependent O-Methyltransferase in the Phenylpropanoid Metabolism of Mesembryanthemum crystallinum

Ibdah

Zhang

Schmidt

et al. 2003

Journal of Biological Chemistry

113

149

View full text Add to dashboard Cite

Upon irradiation with elevated light intensities, the ice plant (Mesembryanthemum crystallinum) accumulates a complex pattern of methylated and glycosylated flavonol conjugates in the upper epidermal layer. Identification of a flavonol methylating activity, partial purification of the enzyme, and sequencing of the corresponding peptide fragments revealed a novel S-adenosyl-L-methionine-dependent O-methyltransferase that was specific for flavonoids and caffeoyl-CoA. Cloning and functional expression of the corresponding cDNA verified that the new methyltransferase is a multifunctional 26.6-kDa Mg 2؉ -dependent enzyme, which shows a significant sequence similarity to the cluster of caffeoyl coenzyme A-methylating enzymes. Functional analysis of highly homologous members from chickweed (Stellaria longipes), Arabidopsis thaliana, and tobacco (Nicotiana tabacum) demonstrated that the enzymes from the ice plant, chickweed, and A. thaliana possess a broader substrate specificity toward o-hydroquinone-like structures than previously anticipated for Mg 2؉ -dependent O-methyltransferases, and are distinctly different from the tobacco enzyme. Besides caffeoyl-CoA and flavonols, a high specificity was also observed for caffeoylglucose, a compound never before reported to be methylated by any plant O-methyltransferase. Based on phylogenetic analysis of the amino acid sequence and differences in acceptor specificities among both animal and plant Omethyltransferases, we propose that the enzymes from the Centrospermae, along with the predicted gene product from A. thaliana, form a novel subclass within the caffeoyl coenzyme A-dependent O-methyltransferases, with potential divergent functions not restricted to lignin monomer biosynthesis.Methylation by S-adenosyl-L-methionine (AdoMet) 1 dependent O-methyltransferases (OMTs) (EC 2.1.1) is a common modification in natural product biosynthesis. Site-specific O-methylation modulates the physiological properties of such compounds and reduces the chemical reactivity of phenolic hydroxyl groups (1). In plants, O-methylation is also required for monolignol biosynthesis and accounts for the structural differences and properties of lignin, which next to cellulose is the most prominent polymer on earth (2).Plant OMTs can be categorized into two major classes (3). Class I includes a group of low molecular weight (23,000 to 27,000) and Mg 2ϩ -dependent OMTs, whereas class II consists of higher molecular weight OMTs of about 38,000 to 43,000 that do not require Mg 2ϩ for catalytic activity. Prominent class II members include caffeic acid, flavonoid, coumarin, and alkaloid OMTs (4 -6). Within the class I OMTs, a group of small caffeoyl coenzyme A OMTs (CCoAOMTs) have been suggested to be key enzymes in the biosynthesis of monolignols, the precursors of gymnosperm and angiosperm lignins (7,8). In angiosperms, this task may also be performed by class II OMTs that are specific for caffeic acid, caffeyl aldehyde, or caffeyl alcohol (COMT) (9 -11). This apparent redundancy results in a cell-and tis...

show abstract

Functional Expression of an Arabidopsis cDNA Clone Encoding a Flavonol 3′-O-Methyltransferase and Characterization of the Gene Product

Cited by 99 publications

References 12 publications

Cytochrome P450 93G1 Is a Flavone Synthase II That Channels Flavanones to the Biosynthesis of Tricin O-Linked Conjugates in Rice

Cytochrome P450 93G1 Is a Flavone Synthase II That Channels Flavanones to the Biosynthesis of Tricin O-Linked Conjugates in Rice

NAC Transcription Factors, NST1 and NST3, Are Key Regulators of the Formation of Secondary Walls in Woody Tissues ofArabidopsis

A Novel Mg2+-dependent O-Methyltransferase in the Phenylpropanoid Metabolism of Mesembryanthemum crystallinum

Contact Info

Product

Resources

About