Molecular cloning of cDNAs coding for three sugarcane enzymes involved in lignification

Full-length cDNAs encoding the monolignol biosynthetic enzymes caffeic acid 3-O-methyltransferase (COMT, EC 2.1.1.6), cinnamoyl-CoA reductase (CCR, EC 1.2.1.44) and cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) were clon ed from sugarcane (Saccharum of;officinarum L.). The encoded proteins (39.6 , 40.1 and 38.7 kDa for COMT, CCR and CAD, respectively) were identified ba sed on their sequence identities with the corresponding enzymes from other plant species. Pairwise comparisons: of deduced amino acid sequences with k nown plant lignification proteins allowed the identification of important c onserved domains and specific functional motifs within these enzymes. Two n ew conserved domains, probably involved in substrate specificity. are descr ibed for COMTs. Phylogenetic: analysis showed a very close evolutionary rel ationship between sugarcane and maize sequences. Southern blot analyses are consistent with the presence of at least two copies of each studied gene i n sugarcane genome. The comt ccr and cad transcripts appear to happen in a parallel way in different sugarcane tissues. The mRNA accumulation patterns suggest a transcriptional regulation of these genes dependent on their spe cific role in lignin synthesis. The cloning and characterisation of sugarca ne genes involved in lignification opens Lip the possibility of producing p lants with lower and, or modified lignin by genetic engineering means. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.