GmAMT2.1/2.2-dependent ammonium nitrogen and metabolites shape rhizosphere microbiome assembly to mitigate cadmium toxicity.

Cadmium (Cd), a heavy metal, is negatively associated with plant growth. AMT (ammonium transporter) genes can confer Cd resistance and enhance nitrogen (N) uptake in soybeans. The potential of AMT genes to alleviate Cd toxicity by modulating rhizosphere microbiota remains unkonwn. Here, the rhizosphere microbial taxonomic and metabolic differences in three genotypes, i.e., double knockout and overexpression lines and wild type, were identified. The results showed that GmAMT2.1/2.2 genes could induce soybean to recruit beneficial microorganisms, such as Tumebacillus, Alicyclobacillus, and Penicillium, by altering metabolites. The bacterial, fungal, and cross-kingdom synthetic microbial communities (SynComs) formed by these microorganisms can help soybean resist Cd toxicity. The mechanisms by which SynComs help soybeans resist Cd stress include reducing Cd content, increasing ammonium (NH₄⁺-N) uptake and regulating specific functional genes in soybeans. Overall, this study provides valuable insights for the developing microbial formulations that enhance Cd resistance in sustainable agriculture.