The cinnamyl alcohol dehydrogenase (CAD) gene family in flax (Linum usitatissimum L.): Insight from expression profiling of cads induced by elicitors in cultured flax cells

Abstract

Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme in the biosynthesis of lignin and lignans as it catalyzes the final step of monolignol biosynthesis, using NADPH as a cofactor. In higher plants, CAD is encoded by a multigene family consisting of three major classes. Based on the recently released flax (Linum usitatissimum L.) whole-genome sequences, in this study we identified six CAD family genes that contain an ADH_N domain and an ADH_zinc_N domain, which suggests that the putative flax CADs (LuCADs) are zinc-dependent alcohol dehydrogenases and members of the plant CAD family. In addition, expression analysis using quantitative real-time PCR revealed spatial variations in the expression of LuCADs in different organs. Comparative analysis between LuCAD enzymatic activity and LuCAD transcripts indicates that the variation of LuCAD enzymatic activities by elicitors is reflected by transcription of LuCADs in flax suspension-cultured cells. Taken together, our genome-wide analysis of CAD genes and the expression profiling of these genes provide valuable information for understanding the function of CADs, and will assist future studies on the physiological role of monolignols associated with plant defense.