Integrative analysis reveals cold acclimation mechanisms in Bambusa multiplex with comparative insights from Bambusa ventricosa and Phyllostachys edulis

Bambusa multiplex (cold-tolerant) and Bambusa ventricosa (cold-sensitive) were introduced to Jiangsu Province, China, beyond their natural distribution ranges, over 25 years ago. However, the mechanisms underlying cold adaptation in B. multiplex remain unclear. In this study, we investigated the physiological and anatomical responses of these two bamboo species under cold stress and conducted comparative analyses of their metabolomic and transcriptomic profiles under both cold and warm conditions. Additionally, we compared these datasets with those of Phyllostachys edulis (Moso bamboo) to gain broader insights into stress response mechanisms in bamboos. The results revealed that B. ventricosa has relatively large, thick leaves with high water content, which may contribute to its cold susceptibility. In contrast, B. multiplex has smaller, thinner leaves with lower water content and higher stomatal density, which likely enhance gas exchange and cold adaptation. Despite differences in leaf morphology, microscopic leaf anatomy (epidermis thickness, cuticle thickness, and bulliform cells) showed no significant variation, suggesting that other factors may drive cold adaptability. Distinct metabolite and gene expression profiles, including those of several transcription factors, were observed between the species under both cold and warm conditions. Specific metabolites, such as proline, catechin, and ABA, as well as stress-related pathways, such as WRKY, MYB, ABA, and proline synthesis, were highly expressed in B. multiplex under cold stress, indicating their role in cold acclimation. Comparisons between B. multiplex (8 upregulated and 11 downregulated pathways), B. ventricosa (10 upregulated and 21 downregulated pathways, including photosynthesis, receptor kinases, and stress pathways), and Moso bamboo (30 upregulated and 12 downregulated pathways) highlighted unique cold adaptation strategies for each species. Moso bamboo presented the most robust cold response, including the upregulation of the WRKY, NAC, MYB, HSF, RNA processing, and ethylene signaling pathways. Furthermore, comparative metabolome analysis revealed that these three bamboo species have evolved distinct adaptations in terms of enzyme activity and gene expression for cold acclimation, whereas core metabolic processes remain conserved.