Molecular Cloning of cDNA from Sugarcane Coding for Caffeic Acid O-Methyltransferase (COMT) Involved in Lignification

Full-length cDNA encoding the monolignol biosynthetic enzymes caffeic acid 3-O-methyltransferase (COMT, EC 2.1.1.6) was cloned from improved population of Saccharum officinarum. Caffeic acid 3-O-methyltransferase catalyzes the conversion of caffeic acid to ferulic acid and of 5-hydroxyferulic acid to sinapic acid. The gene encoding for a protein of 39.6 kDa was identified based on their sequence identities with the corresponding enzymes from other plant species. Pairwise comparisons of deduced amino acid sequences with known plant lignification proteins allowed the identification of important conserved domains and specific functional motifs within these enzymes. Two new conserved domains, probably involved in substrate specificity, are described for COMTs.