COMPARATIVE EFFICIENCY OF DIFFERENT CONSTRUCTS FOR DOWN-REGULATION OFTOBACCO CINNAMYL ALCOHOL-DEHYDROGENASE

A number of research groups have recently succeeded in down regulating cinnamyl alcohol dehydrogenase (CAD EC.1.1.1.195) activity through ge netic engineering with the aim of modifying lignin profiles in plants. In view of the expected extension of this technology to economically important plants, we have tried to obtain additional information on th e best antisense constructs for maximal CAD down regulation using toba cco (Nicotiana tnbacum c-v. Samsun) as a model system. A comparison of different constructs showed that efficiency was greater with homologo us cDNAs (partial or full-length sequence) vs heterologous cDNA. In ad dition, constitutive promoters were, in our hands, more efficient than tissue (xylem) specific promoters. Although a strong down regulation of CAD gene expression was obtained for different transformants at the in vitro stage, a drop in CAD activity reduction was observed for som e of them during development in the greenhouse. These different aspect s are discussed in the context of future applications. (C) 1998 Elsevi er Science Ltd. All rights reserved.