Abstract

O-Methylation of plant secondary metabolites, which plays important roles in the biosynthesis of various natural products and function of plants, is catalyzed by a superfamily of S-adenosyl- L-methionine-dependent O-methyltransferases (OMTs). The objectives of the research were to isolate and characterize OMT-like cDNA clones from Arabidopsis thaliana and Serratula tinctoria , and carry out a phylogenomic analysis of well characterized OMTs to develop a framework phylogenetic tree for predicting putative function and substrate specificity of newly identified gene sequences. Two OMT-like cDNA clones of A. thaliana obtained from TAIR (The Arabidopsis Information Resources) were heterologously expressed for molecular and biochemical characterization. The recombinant proteins did not show enzymatic activity with the substrates tested suggesting that these two putative OMTs genes could be pseudogenes. S. tinctoria accumulates small amounts of 3-methylquercetin as an intermediate for the synthesis of 3,3'-dimethyl derivative.