CLONING AND CHARACTERIZATION OF 2 MAIZE CDNAS ENCODING CINNAMOYL-COA REDUCTASE (CCR) AND DIFFERENTIAL EXPRESSION OF THE CORRESPONDING GENES

Cinnamoyl-CoA Reductase (CCR, EC 1.2.1.44) catalyses the first step of the lignin pathway. Two full-length cDNAs identified by sequence anal ysis as CCR-encoding cDNA's were isolated from a maize root cDNA libra ry. These two cDNAs designated ZmCCR1 and ZmCCR2 exhibit 73% sequence conservation at the nucleotide level for their coding regions and are relatively divergent at their 5'- and 3'-untranslated regions. They bo th contain a common signature which is thought to be involved in the c atalytic site of CCR. Northern blot analysis indicated that ZmCCR2 was expressed at very low levels in roots whereas ZmCCR1 was widely expre ssed in different organs. The high level of ZmCCR1 gene expression alo ng the stalk suggests that the corresponding enzyme is probably involv ed in constitutive lignification.