Baucher M., Chabbert B., Pilate G., Van Doorsselaere J., Tollier M. T., Petit-Conil M., Cornu D., Monties B., Van Montagu M., Inze D., Jouanin L., Boerjan W.
Laboratorium voor Genetica, Department of Genetics, Flanders Interuniversity Institute for Biotechnology (M.B., J.V.D., M.V.M., D.I., W.B.), and Laboratoire Associe de I'Institut National de la Recherche Agronomique (France), Universiteit Gent, K.L. Ledeganckstraat 35, B-9000, Belgium (M.B., D.I.).
Plant Physiol. 1996 Dec;112(4):1479-1490. doi: 10.1104/pp.112.4.1479.
Cinnamyl alcohol dehydrogenase (CAD) catalyzes the last step in the biosynthesis of the lignin precursors, the monolignols. We have down-regulated CAD in transgenic poplar (Populus tremula X Populus alba) by both antisense and co-suppression strategies. Several antisense and sense CAD transgenic poplars had an approximately 70% reduced CAD activity that was associated with a red coloration of the xylem tissue. Neither the lignin amount nor the lignin monomeric composition (syringyl/guaiacyl) were significantly modified. However, phloroglucinol-HCl staining was different in the down-regulated CAD plants, suggesting changes in the number of aldehyde units in the lignin. Furthermore, the reactivity of the cell wall toward alkali treatment was altered: a lower amount of lignin was found in the insoluble, saponified residue and more lignin could be precipitated from the soluble alkali fraction. Moreover, large amounts of phenolic compounds, vanillin and especially syringaldehyde, were detected in the soluble alkali fraction of the CAD down-regulated poplars. Alkaline pulping experiments on 3-month-old trees showed a reduction of the kappa number without affecting the degree of cellulose degradation. These results indicate that reducing the CAD activity in trees might be a valuable strategy to optimize certain processes of the wood industry, especially those of the pulp and paper industry.
肉桂醇脱氢酶（CAD）催化木质素前体（即单木质醇）生物合成的最后一步。我们通过反义策略和共抑制策略下调了转基因杨树（欧洲山杨×银白杨）中的CAD。几个反义及正义CAD转基因杨树的CAD活性降低了约70%，这与木质部组织变红有关。木质素的含量和木质素单体组成（紫丁香基/愈创木基）均未发生显著改变。然而，下调CAD的植株中盐酸间苯三酚染色不同，这表明木质素中醛基单元数量发生了变化。此外，细胞壁对碱处理的反应性也发生了改变：在不溶性皂化残渣中发现的木质素含量较低，并且更多的木质素可从可溶性碱部分沉淀出来。此外，在CAD下调的杨树的可溶性碱部分中检测到大量酚类化合物、香草醛，尤其是丁香醛。对3个月大的树木进行的碱性制浆实验表明，卡伯值降低，而不影响纤维素降解程度。这些结果表明，降低树木中的CAD活性可能是优化木材工业某些工艺，尤其是制浆造纸工业工艺的一种有价值的策略。
