Characterization of flavone synthase I from rice

Lee, Yoon Jung; Kim, Jeong-Ho; Kim, Bong Gyu; Lim, Yoongho; Ahn, Joong‐Hoon

doi:10.5483/bmbrep.2008.41.1.068

Cited by 48 publications

(38 citation statements)

References 12 publications

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“…Thus, our data strongly indicated that a completely different enzyme system is involved in flavone O-glycoside biosynthesis. A recombinant rice FNSI protein (OsFNS1-1), which converted naringenin to apigenin in vitro, was previously reported (Lee et al, 2007). It remains to be elucidated whether the enzyme shows the same activity in planta.…”

Section: Discussionmentioning

confidence: 99%

“…The biosynthesis of flavones was largely unknown in monocots until recent years. A recombinant rice DOX protein, designated as OsFNS1-1, was found to convert naringenin directly to apigenin, and it represented the first FNSI reported outside Apiaceae (Lee et al, 2007). On the other hand, we recently described a sorghum (Sorghum bicolor) pathogen-inducible P450 gene that resulted in the accumulation of 2-hydroxyflavanone O-hexosides in transgenic Arabidopsis (Arabidopsis thaliana; Du et al, 2010).…”

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CYP93G2 Is a Flavanone 2-Hydroxylase Required for C-Glycosylflavone Biosynthesis in Rice

et al. 2010

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C-Glycosylflavones are ubiquitous in the plant kingdom, and many of them have beneficial effects on human health. They are a special group of flavonoid glycosides in which the sugars are C-linked to the flavone skeleton. It has been long presumed that C-glycosylflavones have a different biosynthetic origin from O-glycosylflavonoids. In rice (Oryza sativa), a C-glucosyltransferase (OsCGT) that accepts 2-hydroxyflavanone substrates and a dehydratase activity that selectively converts C-glucosyl-2-hydroxyflavanones to 6C-glucosylflavones were recently described. In this study, we provide in vitro and in planta evidence that the rice P450 CYP93G2 protein encoded by Os06g01250 is a functional flavanone 2-hydroxylase. CYP93G2 is related to the CYP93B subfamily, which consists of dicot flavone synthase II enzymes. In the presence of NADPH, recombinant CYP93G2 converts naringenin and eriodictyol to the corresponding 2-hydroxyflavanones. In addition, CYP93G2 generates 2-hydroxyflavanones, which are modified by O-glycosylation in transgenic Arabidopsis (Arabidopsis thaliana). Coexpression of CYP93G2 and OsCGT in Arabidopsis resulted in the production of C-glucosyl-2-hydroxyflavanones in the dibenzoylmethane tautomeric form. The same structure was reported previously for the in vitro OsCGT reaction products. Thus, CYP93G2 generates 2-hydroxyflavanone substrates from flavanones for C-glucosylation by OsCGT in planta. Furthermore, knocking down Os06g01250 in rice (O. sativa subsp. japonica 'Zhonghua 11') preferentially depleted the accumulation of C-glycosylapigenin, C-glycosylluteolin, and C-glycosylchrysoeriol but did not affect the levels of tricin, which is frequently present as O-glycosides in cereals. Taken together, our work conclusively assigned CYP93G2 as the first enzyme that channels flavanones to C-glycosylflavone biosynthesis in rice.

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Section: Discussionmentioning

confidence: 99%

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CYP93G2 Is a Flavanone 2-Hydroxylase Required for C-Glycosylflavone Biosynthesis in Rice

et al. 2010

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“…None of these flavone metabolites are synthesized by cruciferous plants, including Arabidopsis (Martens and Mithöfer, 2005). Recently, two rice genes (Os10g39140 and Os03g03034) encoding DOX enzymes were reported to show FNSI activities in vitro (Kim et al, 2008;Lee et al, 2008b). In this study, we also generated transgenic Arabidopsis tt6 plants overexpressing either rice gene for metabolite analysis.…”

Section: Transgenic Analysis Of Putative Fnsi and Fnsii Genes In The mentioning

confidence: 99%

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

et al. 2014

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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.

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“…Moreover, AtDMR6's spatial expression was specifically detected at sites that are in direct contact with the pathogen (van Damme et al, 2008). However, two FNSI enzymes described in rice Lee et al, 2008) show high amino acid identity with AtDMR6, suggesting that this protein instead has FNSI activity in Arabidopsis plants.…”

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The Identification of Maize and Arabidopsis Type I FLAVONE SYNTHASEs Links Flavones with Hormones and Biotic Interactions

et al. 2015

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Flavones are a major group of flavonoids with diverse functions and are extensively distributed in land plants. There are two different classes of FLAVONE SYNTHASE (FNS) enzymes that catalyze the conversion of the flavanones into flavones. The FNSI class comprises soluble Fe 2+ /2-oxoglutarate-dependent dioxygenases, and FNSII enzymes are oxygen-and NADPH-dependent cytochrome P450 membrane-bound monooxygenases. Here, we describe the identification and characterization of FNSI enzymes from maize (Zea mays) and Arabidopsis (Arabidopsis thaliana). In maize, ZmFNSI-1 is expressed at significantly higher levels in silks and pericarps expressing the 3-deoxy flavonoid R2R3-MYB regulator P1, suggesting that ZmFNSI-1 could be the main enzyme for the synthesis of flavone O-glycosides. We also show here that DOWNY MILDEW RESISTANT6 (AtDMR6), the Arabidopsis homologous enzyme to ZmFNSI-1, has FNSI activity. While dmr6 mutants show loss of susceptibility to Pseudomonas syringae, transgenic dmr6 plants expressing ZmFNSI-1 show similar susceptibility to wild-type plants, demonstrating that ZmFNSI-1 can complement the mutant phenotype. AtDMR6 expression analysis showed a tissue-and developmental stage-dependent pattern, with high expression in cauline and senescing leaves. Finally, we show that Arabidopsis cauline and senescing leaves accumulate apigenin, demonstrating that Arabidopsis plants have an FNSI activity involved in the biosynthesis of flavones. The results presented here also suggest cross talk between the flavone and salicylic acid pathways in Arabidopsis; in this way, pathogens would induce flavones to decrease salicylic acid and, hence, increase susceptibility.

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Characterization of flavone synthase I from rice

Cited by 48 publications

References 12 publications

CYP93G2 Is a Flavanone 2-Hydroxylase Required for C-Glycosylflavone Biosynthesis in Rice

CYP93G2 Is a Flavanone 2-Hydroxylase Required for C-Glycosylflavone Biosynthesis in Rice

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

The Identification of Maize and Arabidopsis Type I FLAVONE SYNTHASEs Links Flavones with Hormones and Biotic Interactions

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