Rhizosphere microbiome-mediated cadmium and lead mobilization in Erigeron canadensis across a regional contamination gradient: Trade-offs between diversity loss and functional gene enrichment

Erigeron canadensis , an invasive plant with significant biomass and heavy metal tolerance, has the potential for phytoremediation of soil heavy-metal contaminants. This study aimed to screen the key factors for improving the phytoremediation capacity of E. canadensis by examining rhizospheric ecological characteristics under varying levels of heavy metal pollution. Results showed that E. canadensis exhibited greater ability to enrich Cd and Pb in mildly polluted environments, with distinct mechanisms driving this pattern across three groups: HX (Huayuan County), LX (Liuyang City), and YX (Yueyang City), which represented different levels of pollution. Soil properties such as pH, total nitrogen, alkaline-hydrolyzed nitrogen (readily available nitrogen), and organic matter significantly influenced heavy metal uptake. Furthermore, the rhizosphere environment facilitated the adaptation of plant and enrichment of heavy metals by altering the microbial community, specifically by reducing overall diversity while increasing the relative abundance of key taxa characterized by metal resistance and plant growth-promoting abilities, including Lysobacter , Corynebacterium , Humicola , and Colletotrichum . These microorganisms adapted to Cd/Pb stress with some specific genes (e.g., Fur, PerR, and CueR) and enzymes (e.g., P-type ATPases, catalase, and alcohol dehydrogenase) related to heavy metal transport and uptake. This study elucidated the relationship between rhizospheric ecological factors and the regulatory mechanisms of phytoremediation. Selected microbial taxa might be developed as bioinoculants, improving phytoremediation efficiency and enhancing the ecological restoration capacity while also providing insights for the management of invasive species. • Under low pollution, E. canadensis exhibited both improved remediation and root accumulation of Cd/Pb. • Soil pH, nitrogen and organic matter were the key factors in accumulating Cd/Pb of E. canadensis . • Soil Lysobacter , Corynebacterium , and Humicola also affected the Cd/Pb uptake in E. canadensis . • Microbial genes (Fur, PerR, CueR) and enzymes (catalase) might enhance plant Cd/Pb remediation.