Laboratori de Genetica Molecular Vegetal, Centre de Recerca en AgriGenomica (CRAG), Consorci CSIC-IRTA-UAB-UB, Edifici CRAG, Campus UAB, Bellaterra (Cerdanyola del Vallés), Barcelona, Spain.
Mol Plant. 2012 Jul;5(4):817-30. doi: 10.1093/mp/ssr097. Epub 2011 Dec 6.
Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme involved in the last step of monolignol biosynthesis. The effect of CAD down-regulation on lignin production was investigated through a transgenic approach in maize. Transgenic CAD-RNAi plants show a different degree of enzymatic reduction depending on the analyzed tissue and show alterations in cell wall composition. Cell walls of CAD-RNAi stems contain a lignin polymer with a slight reduction in the S-to-G ratio without affecting the total lignin content. In addition, these cell walls accumulate higher levels of cellulose and arabinoxylans. In contrast, cell walls of CAD-RNAi midribs present a reduction in the total lignin content and of cell wall polysaccharides. In vitro degradability assays showed that, although to a different extent, the changes induced by the repression of CAD activity produced midribs and stems more degradable than wild-type plants. CAD-RNAi plants grown in the field presented a wild-type phenotype and produced higher amounts of dry biomass. Cellulosic bioethanol assays revealed that CAD-RNAi biomass produced higher levels of ethanol compared to wild-type, making CAD a good target to improve both the nutritional and energetic values of maize lignocellulosic biomass.
肉桂醇脱氢酶（CAD）是木质素生物合成最后一步的关键酶。通过转基因方法在玉米中研究了 CAD 下调对木质素生产的影响。转基因 CAD-RNAi 植物表现出不同程度的酶活性降低，具体取决于分析的组织，并显示细胞壁组成的改变。CAD-RNAi 茎的细胞壁含有木质素聚合物，S/G 比略有降低，但不影响总木质素含量。此外，这些细胞壁积累了更高水平的纤维素和阿拉伯木聚糖。相比之下，CAD-RNAi 中肋的细胞壁总木质素含量和细胞壁多糖减少。体外降解性测定表明，尽管程度不同，但 CAD 活性抑制所诱导的变化使中肋和茎比野生型植物更易降解。在田间生长的 CAD-RNAi 植物表现出野生型表型，产生了更高量的干生物量。纤维素生物乙醇测定表明，与野生型相比，CAD-RNAi 生物质产生了更高水平的乙醇，这使得 CAD 成为提高玉米木质纤维素生物质营养价值和能量值的一个很好的目标。
