Cinnamyl Alcohol Dehydrogenase from Aralia cordata: Cloning of the cDNA and Expression of the Gene in Lignified Tissues

Abstract

A full-length cDNA clone encoding a subunit of cinnamyl alcohol dehydrogenase (CAD) was isolated from a perennial dicot, Aralia cordata. The identity of the clone was demonstrated by two criteria: (i) the amino acid sequences of peptides derived from the purified CAD protein of A. cordata were highly homologous to regions of the amino acid sequence deduced from the nucleotide sequence of the cDNA; and (ii) a fusion protein expressed from γgtll that carried part of the cDNA reacted with an antibody raised against purified CAD protein. Amino-terminal sequencing of the protein indicated that the mature protein is shorter by two amino acids at the amino terminus than the protein predicted from the nucleotide sequence. The level of expression of the gene was higher in stems than in leaves and roots, consistent with the degree of lignification of these tissues. A comparison of amino acid sequences indicated that CAD is a member of the family of alcohol dehydrogenases.