Integrated physiological, transcriptomic and rhizospheric microbial community analysis unveil the high tolerance of woody bamboo Dendrocalamus brandisii under cadmium toxicity

Cadmium (Cd) can disrupt the physiological functions of plants and affect the soil microenvironment. Previous studies have demonstrated the strong Cd tolerance of woody bamboo species, but the underlying mechanisms remain unclear. Dendrocalamus brandisii is a famous woody bamboo produces highly valued bamboo shoots in SW China and Southeast Asia. To analyze D. brandisii's tolerance mechanisms to Cd stress, changes in physiology, gene expression, and rhizosphere microbial structure were analyzed in a simulated pot experiment, by exposing D. brandisii to different Cd concentrations. According to the results, the roots are the main sites for Cd accumulation. Transmission electron microscopy (TEM) demonstrated that excess Cd induced damage to plant organ cell ultrastructure, as chloroplast structural abnormalities and deformations in cell walls. Based on transcriptome analysis, some key DEGs and their involved pathways, such as metal transporters were identified to perform crucial roles in Cd tolerance. In addition, Cd significantly affects soil pH and further influences microbial community structure. Under Cd stress, the increased abundance of Proteobacteria and Ascomycota likely facilitated Cd tolerance in D. brandisii. Overall, the physiological characteristics of D. brandisii and beneficial rhizospheric microbes may improve the Cd tolerance in this bamboo, implying woody bamboos are a promising environment-restoration plant. These results provide important information for further research on multifunctional genes of Cd tolerance and selective changes in rhizosphere microbial communities.