Comparative physiological, transcriptomic and metabolomic analyses reveal the mechanisms underlying the exceptionally long internodes in bamboo (Bambusa distegia)

Bamboo has emerged as a globally significant sustainable resource, playing an increasingly vital role in "bamboo-for-plastic" initiatives and other green industries. Internode length represents a key agronomic trait that determines fiber yield and processing efficiency in bamboo. To elucidate the mechanisms governing internode elongation, this study investigated Bambusa distegia, a species characterized by exceptionally long internodes (over 100 cm). Comparative analysis of growth dynamics with Phyllostachys edulis and Dendrocalamus farinosus, and cytological comparison between B. distegia and P. edulis, revealed that B. distegia exhibited a growth duration of approximately 60 days for its longest internode, compared to ~20 days for P. edulis and ~40 days for D. farinosus, indicating that the extended internodes in B. distegia originate from prolonged growth duration and increased cell number, rather than accelerated elongation rate or enhanced cell length. Integrated histological, transcriptomic, and metabolomic analyses demonstrated that sustained cytokinin signaling serves as the key mechanism maintaining prolonged cell division activity. Through weighted gene co-expression network analysis (WGCNA) and co-expression network construction, core regulatory factors were identified, including cytokinin biosynthetic enzymes (CYP735A), modifying enzymes (UGT85A), cell cycle regulators (CYCD3/CYCA3), and key transcription factors (ERF, TCP14). This study systematically clarifies the molecular basis of long internode formation in bamboo and provides valuable genetic targets and theoretical support for breeding industrial bamboo varieties with optimized internode structure and enhanced utilization efficiency, thereby promoting sustainable utilization and value-added development of bamboo resources.