Identification of a flavonol 7-O-rhamnosyltransferase gene determining flavonoid pattern in Arabidopsis by transcriptome coexpression analysis and reverse genetics

J Biol Chem. 2007 May 18;282(20):14932-41. doi: 10.1074/jbc.M611498200. Epub 2007 Feb 21.


Glycosylation plays a major role in the remarkable chemical diversity of flavonoids in plants including Arabidopsis thaliana. The wide diversity encoded by the large family-1 glycosyltransferase (UGT) gene family makes it difficult to determine the biochemical function of each gene solely from its primary sequence. Here we used transcriptome coexpression analysis combined with a reverse genetics approach to identify a gene that is prominent in determining the flavonoid composition of Arabidopsis. Using transcriptome coexpression analysis accessible on the ATTED-II public data base, the expression pattern of a UGT gene, UGT89C1, was found to be highly correlated with known flavonoid biosynthetic genes. No C-7 rhamnosylated flavonols were detected in either of two T-DNA ugt89c1 mutants. This specific metabolite deficiency in the mutants was complemented by stable transformation with the genomic fragment containing intact UGT89C1. Glutathione S-transferasefused recombinant UGT89C1 protein converted kaempferol 3-O-glucoside to kaempferol 3-O-glucoside-7-O-rhamnoside and recognized 3-O-glycosylated flavonols and UDP-rhamnose as substrates, but not flavonol aglycones, 3-O-glycosylated anthocyanins or other UDP-sugars. These results show that UGT89C1 is a flavonol 7-O-rhamnosyltransferase. The abundance of UGT89C1 transcripts in floral buds was consistent with the flavonoid accumulation of C-7 rhamnosylated flavonols in Arabidopsis organs. Our present study demonstrates that the integration of transcriptome coexpression analysis with a reverse genetic approach is a versatile tool for understanding a multigene family of a metabolic pathway in Arabidopsis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthocyanins / metabolism
  • Arabidopsis / enzymology
  • Arabidopsis / genetics*
  • Arabidopsis Proteins / biosynthesis
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Flavonols / metabolism
  • Gene Expression
  • Gene Expression Regulation, Enzymologic / physiology*
  • Gene Expression Regulation, Plant / physiology*
  • Hexosyltransferases / biosynthesis
  • Hexosyltransferases / genetics*
  • Hexosyltransferases / metabolism
  • Kaempferols / biosynthesis
  • Transcription, Genetic / physiology*


  • Anthocyanins
  • Arabidopsis Proteins
  • Flavonols
  • Kaempferols
  • kaempferol 3-rhamnosyldiglucoside
  • Hexosyltransferases
  • UGT89C1 protein, Arabidopsis