Structural and compositional modifications in lignin of transgenic alfalfa down-regulated in caffeic acid 3-O-methyltransferase and caffeoyl coenzyme A 3-O-methyltransferase
Structural and compositional modifications in lignin of transgenic alfalfa down-regulated in caffeic acid 3-O-methyltransferase and caffeoyl coenzyme A 3-O-methyltransferase
复制标题
DOI：
10.1016/s0031-9422(02)00434-x
复制
发表时间：
2003-01-01
期刊：
影响因子：
3.8
通讯作者：
Dixon, RA
中科院分区：
文献类型：
--
作者：
Marita, JM;Ralph, J;Dixon, RA
从缺乏咖啡酸 3-O-甲基转移酶的苜蓿中分离出的木质素含有苯并二恶烷，这是由于掺入了新型单体 5-羟基松柏醇而产生的。由于可溶性木质素成分中的含量很高，并且使用了灵敏的核磁共振仪器，因此揭示了独特的结构特征。鉴定出一种新型末端单元，即 5-羟基愈创木酰甘油单元。可以确定松柏醇、芥子醇和新型 5-羟基松柏醇可以与木质素中形成的 5-羟基愈创木基单元交叉偶联，后者产生苯并二恶烷单元的长链。还有证据表明 5-羟基松柏醇与正常（愈创木基或紫丁香基）木质素单元偶联。缺乏咖啡酰辅酶A 3-O-甲基转移酶的苜蓿中的木质素在结构上与对照木质素相似，但转基因表现出木质素含量显着降低（接近20%）和纤维素适度增加（接近10%），反映出纤维素：木质素比率增加了30%。两种转基因成分的变化可能通过提高苜蓿茎部分的消化率来增强苜蓿作为主要饲料作物的利用。由爱思唯尔科学有限公司出版
Isolated lignins from alfalfa deficient in caffeic acid 3-O-methyltransferase contained benzodioxanes resulting from the incorporation of the novel monomer, 5-hydroxyconiferyl alcohol. Due to the high level incorporated into the soluble lignin fraction and the use of sensitive NMR instrumentation, unique structural features were revealed. A new type of end-unit, the 5-hydroxyguaiacyl glycerol unit, was identified. It was possible to establish that coniferyl alcohol, sinapyl alcohol, and the novel 5-hydroxyconiferyl alcohol can cross-couple with the 5-hydroxyguaiacyl units that are formed in the lignin, the latter giving rise to extended chains of benzodioxane units. There is also evidence that 5-hydroxyconiferyl alcohol couples with normal (guaiacyl or syringyl) lignin units. Lignin in the alfalfa deficient in caffeoyl CoA 3-O-methyltransferase was structurally similar to the control lignin but the transgenic exhibited a dramatic decrease in lignin content (similar to20%) and modest increase in cellulose (similar to10%) reflecting a 30% increase in cellulose:lignin ratio. The compositional changes in both transgenics potentially allow enhanced utilization of alfalfa as a major forage crop by increasing the digestibility of its stem fraction. Published by Elsevier Science Ltd.