CYP93G2 is a flavanone 2-hydroxylase required for C-glycosylflavone biosynthesis in rice

Plant Physiol. 2010 Sep;154(1):324-33. doi: 10.1104/pp.110.161042. Epub 2010 Jul 20.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Chromatography, Liquid
  • Cytochrome P-450 Enzyme System / metabolism*
  • DNA, Bacterial / genetics
  • Flavones / biosynthesis*
  • Flavones / chemistry
  • Glycosides / biosynthesis*
  • Glycosides / chemistry
  • Mass Spectrometry
  • Molecular Sequence Data
  • Mutagenesis, Insertional / genetics
  • Oryza / enzymology*
  • Oryza / genetics
  • Phylogeny
  • Plant Leaves / metabolism
  • Plants, Genetically Modified
  • Recombinant Proteins / metabolism
  • Sequence Analysis, Protein
  • Sequence Homology, Amino Acid
  • Sorghum / enzymology
  • Substrate Specificity


  • DNA, Bacterial
  • Flavones
  • Glycosides
  • Recombinant Proteins
  • T-DNA
  • Cytochrome P-450 Enzyme System
  • cytochrome P-450 CYP93B1 (Glycyrrhiza echinata)

Associated data

  • GENBANK/AK071127
  • GENBANK/AK099468