Bacillus velezensis ZM202201 enhances cadmium tolerance in wheat by reinforcing antioxidant defense and modulating metal detoxification pathways

• Bacillus velezensis enhances wheat resistance against Cd stress • B. velezensis increases antioxidant capacity in Cd-stressed wheat • B. velezensis modulates gene expressions of wheat under Cd condition • B. velezensis is a potential microbial inoculant for sustainable wheat cultivation Cadmium (Cd) contamination in agricultural soils poses a significant threat to wheat production and global food safety. Plant growth-promoting bacteria (PGPB) offer a sustainable and environmentally compatible approach for mitigating heavy metal stress. In this study, we investigated the mechanisms through which Bacillus velezensis ZM202201 enhances Cd stress tolerance in wheat. The strain exhibited multiple plant growth-promoting attributes, including indole-3-acetic acid production, siderophore secretion, and nitrogen-fixing ability, along with a high intrinsic Cd resistance. Under Cd exposure, inoculation with ZM202201 significantly improved plant growth parameters (plant height, root length, and biomass) and reduced oxidative damage, as evidenced by lower malondialdehyde (29.8%) and hydrogen peroxide (19.7%) accumulation. These protective effects were associated with enhanced antioxidant capacity, reflected by increased activities of superoxide dismutase, peroxidase, and catalase. Transcriptomic profiling further revealed that inoculation withZM202201 activated Cd detoxification pathways, particularly by upregulating ABCC-type transporters involved in vacuolar sequestration while downregulating specific heavy metal-associated isoprenylated plant proteins. Weighted gene co-expression network analysis identified key gene modules and hub regulators linked to metal transport and redox homeostasis. Collectively, these findings demonstrate that ZM202201 enhances wheat tolerance to Cd by reinforcing antioxidant defense and reprogramming metal detoxification pathways, highlighting its potential as a microbial inoculant for sustainable wheat cultivation in Cd-contaminated soils.