Divergent evolution of flavonoid 2-oxoglutarate-dependent dioxygenases in parsley

FEBS Lett. 2003 Jun 5;544(1-3):93-8. doi: 10.1016/s0014-5793(03)00479-4.


Flavone synthases (FNSs) catalyze the oxidation of flavanones to flavones, i.e. the formation of apigenin from (2S)-naringenin. While many plants express a microsomal-type FNS II, the soluble FNS I appears to be confined to a few species of the Apiaceae and was cloned recently from parsley plants. FNS I belongs to the Fe(II)/2-oxoglutarate-dependent dioxygenases characterized by short conserved sequence elements for cofactor binding, and its evolutionary context and mode of action are under investigation. Using a homology-based reverse transcription polymerase chain reaction approach, two additional flavonoid-specific dioxygenases were cloned from immature parsley leaflets, which were identified as flavanone 3beta-hydroxylase (FHT) and flavonol synthase (FLS) after expression in yeast cells. Sequence alignments revealed marginal differences among the parsley FNS I and FHT polypeptides of only 6%, while much less identity (about 29%) was observed with the parsley FLS. Analogous to FNS I, FLS oxidizes the flavonoid gamma-pyrone by introducing a C2, C3 double bond, and (2R,3S)-dihydrokaempferol (cis-dihydrokaempferol) was proposed recently as the most likely intermediate in both FNS I and FLS catalysis. Incubation of either FNS I or FLS with cis-dihydrokaempferol exclusively produced kaempferol and confirmed the assumption that flavonol formation occurs via hydroxylation at C3 followed by dehydratation. However, the lack of apigenin in these incubations ruled out cis-dihydrokaempferol as a free intermediate in FNS I catalysis. Furthermore, neither (+)-trans-dihydrokaempferol nor unnatural (-)-trans-dihydrokaempferol and 2-hydroxynaringenin served as a substrate for FNS I. Overall, the data suggest that FNS I has evolved uniquely in some Apiaceae as a paraphyletic gene from FHT, irrespective of the fact that FNS I and FLS catalyze equivalent desaturation reactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Chromatography, Thin Layer
  • Cloning, Molecular
  • DNA, Complementary / metabolism
  • Evolution, Molecular
  • Models, Chemical
  • Molecular Sequence Data
  • Oxidoreductases / chemistry*
  • Oxidoreductases / pharmacology*
  • Oxygen / metabolism
  • Peptides / chemistry
  • Petroselinum / enzymology*
  • Phylogeny
  • Plant Proteins*
  • Polymerase Chain Reaction
  • Recombinant Proteins / chemistry
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Homology, Amino Acid
  • Substrate Specificity


  • DNA, Complementary
  • Peptides
  • Plant Proteins
  • Recombinant Proteins
  • Oxidoreductases
  • flavonol synthase
  • Oxygen

Associated data

  • GENBANK/AY230247
  • GENBANK/AY230248
  • GENBANK/AY230249