Poplar is a key player in biomass resource and a dominant species for lignocellulosic biofuel production around the world. Today, the use of poplars is mainly concentrated in the aboveground parts. However, as an important part of trees, the poplar root system developed, roots account for about 20 % of the volume of the tree, and the root material volume is very considerable and its utilization potential is huge. The root lignin is central to biomass production in poplar. However, there are very few studies on root lignin structure. Recently, we found a root-specific transcription factor, NUCLEAR FACTOR Y subunit B21 (NF-YB21), is involved in regulating root growth and lignification. In the present study, physiology, transgenosis, transcriptomics, metabolome, Confocal Raman Microscopy (CRM) and Nuclear Magnetic Resonance (NMR) techniques were performed to further investigate the regulatory mechanisms of PdNF-YB21 on lignin structure in poplar roots. The results of transcriptome and metabolome showed that there were more genes and metabolites related to S-lignin synthesis in transgenic plants. Root firmness measurements, CRM and NMR results showed that overexpression of PdNF-YB21 dramatically improved root hardness, increased root lignin content and S/G ratio, and increased the concentrations of glucan, xylan and lignin in roots, which promoted root growth. In short, this present study not only illustrated the regulatory mechanisms of PdNF-YB21 on lignin structure in poplar roots, but also proposed a directive breeding of new poplar species for current biorefinery process.

杨树是生物质资源的主要参与者，也是世界范围内木质纤维素生物燃料生产的主要物种。如今，杨树的使用主要集中在地上部分。但是，作为树木的重要组成部分，杨树的根系发达，根系约占树木体积的20％，根系物质的体积非常可观，其利用潜力巨大。木质素是杨树生物量生产的核心。但是，关于根木质素结构的研究很少。最近，我们发现了根特异性转录因子NUCLEAR FACTOR Y亚基B21（NF-YB21），参与调节根的生长和木质化。在本研究中，进行了生理学，转基因，转录组学，代谢组学，共聚焦拉曼显微镜（CRM）和核磁共振（NMR）技术，以进一步研究PdNF-YB21对杨树根木质素结构的调控机制。转录组和代谢组的结果表明，转基因植物中与S-木质素合成相关的基因和代谢产物更多。根系硬度测量，CRM和NMR结果表明PdNF-YB21过表达显着提高了根部硬度，增加了根部木质素含量和S / G比，并增加了根中葡聚糖，木聚糖和木质素的浓度，从而促进了根部生长。简而言之，本研究不仅阐明了PdNF-YB21对杨树根中木质素结构的调控机制，而且还提出了针对当前生物精炼工艺的新杨树种的定向育种。