Fen Yu

The bamboo shoot is a crucial component of bamboo forest economy. Previous studies have demonstrated that rapid lignification occurs during the postharvest storage of bamboo shoots. However, the mechanism underlying rapid lignification after bamboo shoot harvesting remains unclear. To explore this phenomenon in Moso bamboo (Phyllostachys edulis (Carrière) J. Houz.) shoots, we employed morphological, cytological, lignin content determination, and transcriptomic analysis methods. Our results indicated that the optimal consumption period is within 12–24 h postharvest. We identified 19,038 differentially expressed genes (DEGs), with the majority enriched in pathways related to stress response, photosynthesis, and the biosynthesis of phenylalanine, abscisic acid, and jasmonic acid (JA). Additionally, copy number analysis of ten enzyme-coding genes involved in lignin synthesis revealed the regulatory network of lignin synthesis following shoot harvesting. The study offers insights into the rapid lignification process in bamboo shoots postharvest, potentially regulated by stress responses and JA. Feasible preservation methods were also explored to extend the storage duration at room temperature.

The Moso bamboo culm neck, connected with the rhizome and the shoot bud, is an important hub for connecting and transporting the aboveground and belowground systems of bamboo for the shoot bud development and rapid growth. Our previous study revealed that the culm neck generally undergoes six different developmental stages (CNS1–CNS6), according to the primary thickening growth of the underground shoot bud. However, the molecular mechanism of the culm neck development remains unknown. The present study focused on the developmental process of the CNS3–CNS5 stages, representing the early, middle, and late elongation stages, respectively. These stages are densely packed with vascular tissues and consist of epidermis, hypodermis, cortex, and ground tissue. Unlike the hollow structure of the culms, the culm necks are solid structures. As the culm neck continues to grow, the lignin deposition increases noticeably, contributing to its progressive strengthening. For the transcriptome analysis, a total of 161,160 transcripts with an average length of 2373 were obtained from these stages using both PacBio and Illumina sequencing. A total of 92.2% of the reads mapped to the Moso bamboo reference genome. Further analysis identified a total of 5524 novel genes and revealed a dynamic transcriptome. Secondary-metabolism- and transport-related genes were upregulated particularly with the growth of the culm neck. Further analysis revealed the molecular processes of lignin accumulation in the culm neck, which include differentially expressed genes (DEGs) related to cell wall loosening and remodeling and secondary metabolism. Moreover, the upregulations of transcription factors such as MYBH and RSM in the MYB family play crucial roles during critical transitions in the culm neck development, such as changes in the angle between the rhizome and the culm neck. Our new findings provide essential insights into the cellular roadmaps, transcriptional networks, and key genes involved in the culm neck development.