Baucher M, Bernard-Vailhé M A, Chabbert B, Besle J M, Opsomer C, Van Montagu M, Botterman J
Departement Genetica, Vlaams Interuniversitair Instituut voor Biotechnologie, Universiteit Gent, Belgium.
Plant Mol Biol. 1999 Feb;39(3):437-47. doi: 10.1023/a:1006182925584.
To improve the digestibility of the forage crop alfalfa (Medicago sativa L.), cinnamyl alcohol dehydrogenase (CAD), which catalyses the last step in the biosynthesis of the lignin monomers, was down-regulated by using an antisense approach. A subset of six transgenic lines with reduced CAD activity and control lines were analysed when grown in the greenhouse and in the field. The down-regulation of the CAD enzyme was associated with a red coloration of the stem. The lignin quantity remained unchanged, but the lignin composition, as determined by thioacidolysis, was altered. The highest reduction of CAD activity was associated with a lower syringyl/guaiacyl (S/G) ratio and a lower S+G yield, mainly because of a decreased amount of S units. An increase in in situ disappearance of dry matter and of cell wall residue was detected in one of the transgenic lines grown in the greenhouse, and for two of the lines grown in the field the rate of disappearance of dry matter slightly improved. Furthermore, these two lines had a higher solubility in alkali as shown by the lower yield of saponified residue. This study opens perspectives for improving forage crop digestibility by the modulation of enzymes involved in lignin biosynthesis.
为提高饲料作物苜蓿（紫花苜蓿）的消化率，通过反义技术下调了催化木质素单体生物合成最后一步的肉桂醇脱氢酶（CAD）。对6个CAD活性降低的转基因株系和对照株系的一个子集在温室和田间种植时进行了分析。CAD酶的下调与茎的红色有关。木质素含量保持不变，但硫代酸解测定的木质素组成发生了改变。CAD活性的最大降低与较低的紫丁香基/愈创木基（S/G）比和较低的S+G产量相关，主要是由于S单元数量减少。在温室种植的一个转基因株系中检测到干物质和细胞壁残渣原位消失增加，在田间种植的两个株系中，干物质消失率略有提高。此外，这两个株系的碱溶性更高，皂化残渣产量更低。本研究为通过调节参与木质素生物合成的酶来提高饲料作物消化率开辟了前景。
