Koshiba Taichi, Yamamoto Naoki, Tobimatsu Yuki, Yamamura Masaomi, Suzuki Shiro, Hattori Takefumi, Mukai Mai, Noda Soichiro, Shibata Daisuke, Sakamoto Masahiro, Umezawa Toshiaki
Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan.
Kazusa DNA Research Institute, Kisarazu, Chiba 292-0818, Japan.
Plant Biotechnol (Tokyo). 2017;34(1):7-15. doi: 10.5511/plantbiotechnology.16.1201a. Epub 2017 Mar 17.
Lignin encrusts lignocellulose polysaccharides, and has long been considered an obstacle for the efficient use of polysaccharides during processes such as pulping and bioethanol fermentation. However, lignin is also a potential feedstock for aromatic products and is an important by-product of polysaccharide utilization. Therefore, producing biomass plant species exhibiting enhanced lignin production is an important breeding objective. Herein, we describe the development of transgenic rice plants with increased lignin content. Five (Arabidopsis) and one (rice) MYB transcription factor genes that were implicated to be involved in lignin biosynthesis were transformed into rice ( L. ssp. cv. Nipponbare). Among them, three Arabidopsis MYBs (, , and ) in transgenic rice T lines resulted in culms with lignin content about 1.5-fold higher than that of control plants. Furthermore, lignin structures in -overexpressing rice plants were investigated by wet-chemistry and two-dimensional nuclear magnetic resonance spectroscopy approaches. Our data suggested that heterologous expression of in rice increased lignin content mainly by enriching syringyl units as well as -coumarate and tricin moieties in the lignin polymers. We contemplate that this strategy is also applicable to lignin upregulation in large-sized grass biomass plants, such as , switchgrass, and .
木质素包裹着木质纤维素多糖，长期以来一直被认为是制浆和生物乙醇发酵等过程中多糖高效利用的障碍。然而，木质素也是芳香族产品的潜在原料，并且是多糖利用的重要副产物。因此，培育木质素产量提高的生物质植物品种是一个重要的育种目标。在此，我们描述了木质素含量增加的转基因水稻植株的培育情况。五个（拟南芥）和一个（水稻）与木质素生物合成相关的MYB转录因子基因被转入水稻（L. ssp. cv. 日本晴）。其中，转基因水稻T代株系中的三个拟南芥MYB（、和）导致茎秆木质素含量比对照植株高约1.5倍。此外，通过湿化学和二维核磁共振光谱方法研究了过表达水稻植株中的木质素结构。我们的数据表明，在水稻中异源表达主要通过在木质素聚合物中富集紫丁香基单元以及对香豆酸和小麦黄素部分来增加木质素含量。我们认为这种策略也适用于大型禾本科生物质植物如、柳枝稷、和中的木质素上调。
