Antibiotic resistome patterns across wheat soil microdomains under cadmium exposure and their associations with rhizosphere metabolite profiles.

The co-contamination of heavy metals and antibiotic resistance genes (ARGs) poses an increasing challenge to agroecosystems, yet its relationships with rhizosphere metabolism and microbial communities remain poorly understood. We integrated metagenomic sequencing, untargeted metabolomics, and absolute qPCR in a wheat pot experiment to characterize resistome patterns across unplanted bulk soil (O), root-zone soil (PS), and rhizosphere soil (PR) under three Cd treatments. At the booting stage, observed ARG subtype richness and total TPM-normalized ARG abundance were higher in root-associated compartments, whereas responses to cadmium within PR were heterogeneous and non-monotonic. Absolute qPCR broadly supported enrichment of selected resistance genes in root-associated soils. Community analyses identified Pseudomonadota and Actinomycetota as potential ARG-associated taxa. Metabolomic differentiation between PR and O was substantially greater than the differences among Cd treatments within PR, while metabolite-ARG associations partly reflected compartment-level covariation. ARG and metal resistance gene abundances showed strong covariation relationship, and contig-level analysis identified genetic contexts consistent with potential linkage among resistance determinants across both control and Cd-amended treatments. Overall, spatial differentiation among soil microdomains was more consistent than treatment-associated Cd patterns. These findings identify the wheat rhizosphere as an important zone of ARG enrichment under Cd exposure while highlighting the need for host-resolved and functional validation.