PdNF-YB21 positively regulated root lignin structure in poplar

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.