Molecular characterization of a cDNA encoding caffeoyl-coenzyme A 3 -O- methyltransferase of Stellaria longipes.

ABSTRACT

A cDNA clone encoding S-adenosyl-L-methionine trans-caffeoyl-CoA 3-O-methyltransferase (EC 2·1·1·104; CCoAOMT) from Stellana longipes Goldie (long-stalked chickweed) was isolated and studied. Structural analysis of both the nucleotide sequence and the predicted amino acid sequence suggests that our cloned sequence encoded a CCoAOMT enzyme of Stellaria longipes, which shared overall structural similarity with other plant CCoAOMTs but exhibited certain distinct characteristics. Southern blot hybridization and cloning analyses indicating a small CCoAOMT gene family in the Stellana longipes genome and the absence of introns in the coding region of the cDNA- corresponding gene. Sequence variations in the coding region were found among three genotypes from geographically isolated populations. Higher levels of CCoAOMT mRNA were detected in stems and leaves than in roots. The cDNAencoded protein expressed in Eschendia coli was shown to utilize caffeoyl-CoA, but not caffeic acid or 5-hydroxy ferulic acid, as its substrate.