Nitrogen fertilization in bamboo forest accelerates the shoot growth and alters the lignification process in shoots

As one of the key nutrients, nitrogen is a major driving force for plant growth and development, and ultimately contributes to biomass improvement. However, little is known about the common genetic basis of bamboo growth with nitrogen fertilization in forests. Here, the physiological-biochemical characteristics showed that nitrogen fertilization in moso bamboo forest obviously affected the activities of multiple enzymes in bamboo shoots, which led to changes in metabolite content. The lignin content was significantly inhibited in bamboo shoots during the early stages of fast growth (from 1.0 m to 4.0 m), while the content was subsequently promoted at the late stage, which resulted in a lignin content similar to that of the control observed in 8.0 m shoots. By integrating the physiological-biochemical and transcriptome data, we generated a global map of changes in the transcriptomic dynamics during fast growth, which showed that upregulated DEGs in 1.0 m and 4.0 m shoots were significantly enriched in growth- and development-related GO terms, while those DEGs in 8.0 m shoots were enriched in lignin biosynthesis-related GO terms. Using weighted correlation network analysis (WGCNA), two complex regulatory networks were constructed: two key structural genes (KSGs) and 118 transcription factors (TFs) involved in nitrogen metabolism and 17 KSGs and 102 TFs involved in lignin biosynthesis. Furthermore, the regulatory mechanism of KSGs targeted by TFs was validated by yeast one-hybrid assays. Overall, nitrogen fertilization differentially affected moso bamboo shoots at different fast growth stages through the expression of genes involved in multiple metabolic pathways, indicating that moso bamboo has plasticity to environmental factors. These results provide a better understanding of the changing patterns in moso bamboo shoots and lay a foundation for the genetic improvement and sustainable management of bamboo forests via nitrogen fertilization.