Lignin is an aromatic polymer and macromolecular organic material and is one of the major components of plant cellular walls. It provides mechanical support for plants and protection against pathogen invasion. Caffeoyl-CoA O-methyltransferase (CCoAOMT) is recognized to be involved in phenylpropanoid metabolism and lignin synthesis, and plays an important role in precursor synthesis of G-lignin units. In this study, a gene encoding CCoAOMT (Genbank ID: AY860952) was isolated from birch (Betula platyphylla Suk.). The predicted BpCCoAOMT polypeptide had high affinity with CCoAOMT from other species. Real-time quantitative polymerase chain reaction (RT-qPCR) results revealed that BpCCoAOMT is most highly expressed in young stems. To study its function in vivo, antisense BpCCoAOMT complementary deoxyribonucleic acid (cDNA) was transformed into tobacco (SR-1) by the Agrobacterium tumefaciens-mediated method. The expression of NtCCoOAMT in antisense BpCCoAOMT transgenic tobacco was down-regulated and total lignin content of transgenic plants decreased by 39% compared to control plants. Maüle reagent was used to distinguish lilac lignin and guaiac wood lignin in situ, which enables S-lignin to exhibit a specific red response. Results revealed that all transgenic tobacco plants were dark brown, while controls were dark red. This indicated that S-lignin content in the xylem was reduced. Compared to wild-type (WT) plants, transgenic tobacco plants had delayed flowering and some had slender stems, curling, and easy lodging. This indicates that the decrease in lignin content interferes with the normal growth of plants.

中文翻译：

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白桦的反义BpCCoAOMT基因的异位表达。木质素含量降低影响烟草的生长发育

木质素是一种芳香族聚合物和高分子有机材料，是植物细胞壁的主要成分之一。它为植物提供机械支持并防止病原体入侵。咖啡酰-CoA O-甲基转移酶（CCoAOMT）被认为与苯丙烷代谢和木质素合成有关，并且在G-木质素单元的前体合成中起重要作用。在这项研究中，从桦树（Betula platyphylla Suk。）分离出编码CCoAOMT（Genbank ID：AY860952）的基因。预测的BpCCoAOMT多肽与其他物种的CCoAOMT具有高亲和力。实时定量聚合酶链反应（RT-qPCR）结果表明BpCCoAOMT在幼茎中表达最高。为了研究其在体内的功能，通过根癌农杆菌介导的方法将反义BpCCoAOMT互补脱氧核糖核酸（cDNA）转化为烟草（SR-1）。NtCCoOAMT在反义BpCCoAOMT中的表达转基因烟草被下调，与对照植物相比，转基因植物的总木质素含量降低了39％。使用Maüle试剂在原位区分丁香木质素和愈创木脂木素，从而使S-木质素表现出特定的红色反应。结果显示，所有转基因烟草植物均为深棕色，而对照为深红色。这表明木质部中的S-木质素含量降低。与野生型（WT）植物相比，转基因烟草植物的开花延迟，有些具有细长的茎，卷曲和易于倒伏。这表明木质素含量的降低会干扰植物的正常生长。