MOLECULAR CHARACTERIZATION OF A CDNA-ENCODING CAFFEOYL COENZYME-A 3-O-METHYLTRANSFERASE OF STELLARIA LONGIPES

A cDNA clone encoding S-adenosyl-L-methionine: trans-caffeoyl-CoA 3-O- methyltransferase (EC 2.1.1.104; CCoAOMT) from Stellaria longipes Gold ie (long-stalked chickweed) was isolated and studied. Structural analy sis of both the nucleotide sequence and the predicted amino acid seque nce suggests that our cloned sequence encoded a CCoAOMT enzyme of Stel laria longipes, which shared overall structural similarity with other plant CCoAOMTs but exhibited certain distinct characteristics. Souther n blot hybridization and cloning analyses indicating a small CCoAOMT g ene family in the Stellaria longipes genome and the absence of introns in the coding region of the cDNA-corresponding gene, Sequence variati ons in the coding region were found among three genotypes from geograp hically isolated populations. Higher levels of CCoAOMT mRNA mere detec ted in stems and leaves than in roots. The cDNA-encoded protein expres sed in Escherichia coli was shown to utilize caffeoyl-CoA, but not caf feic acid or 5-hydroxy ferulic acid, as its substrate.