Microbial reassembly-driven multi-niche functional compensation alleviates uranium stress in rapeseed.

BACKGROUND: Uranium (U) pollution harms soil and plants. It is still unclear how microbes help plants survive uranium stress in different root and leaf environments. OBJECTIVES: In this study, We examined how soil microbial reassembly affects rapeseed growth and the microbes living in soil, roots, and leaves under uranium stress, and explored the functional compensation mechanisms involved. METHODS: A pot experiment was conducted with rapeseed grown in three soil backgrounds (original, sterilized, sterilized-inoculated) under control and 150 mg⋅kg-1 uranium stress. Plant growth, uranium content, and 16S rRNA sequences from four niches (bulk soil, rhizosphere, roots, leaves) were analyzed. RESULTS: Uranium predominantly accumulated in roots, with limited translocation to shoots. Uranium stress increased chlorophyll content but still induced chlorosis. Ecological niche shaped microbial community structure more strongly than soil treatment or uranium stress. Even though the microbial community did not fully return to its original state, it became enriched with uranium-tolerant, growth-promoting bacteria (e.g., Mesorhizobium, Streptomyces, Castellaniella). The reassembled community was associated with alleviated photosynthetic damage and improved phenotype under uranium stress. CONCLUSION: Niche differentiation primarily drives community assembly, and maximizing function does not require complete structural restoration. The naturally enriched multifunctional consortia under uranium stress provide a promising basis for plant-microbe combined remediation.