Metarhizium anisopliae Mitigates the Phytotoxicity of Lead and Nanoplastics on Rice by Modifying Physiological, Transcriptomic, Metabolomic Activities, and Soil Microbiome

Polyethylene nanoplastics (NP) and lead (Pb) increasingly co-occur in agriculture, where their effects exacerbate phytotoxic impacts. We tested whether the endophytic entomopathogenic fungus, Metarhizium anisopliae, can mitigate individual or combined stress of NP and Pb in rice by examining fungus-soil-plant mechanisms using physiological assays, transcriptomics, metabolomics, and rhizosphere microbiome profiling. Rice seedlings were grown under eight treatments (individual or combined stress of Pb and NP, with or without M. anisopliae). Individual and combined Pb and NP stress reduced seedling growth, chlorophyll content, and hormonal levels, while increasing oxidative damage. Pb and NP interactions showed synergistic toxicity, causing severe growth suppression and lipid peroxidation, and repressing photosynthesis and hormone-related pathways. M anisopliae inoculation alleviated these effects and enhanced rice growth by reducing Pb uptake and translocation, restoring antioxidant and hormonal balance, and up-regulating pathways including flavonoid biosynthesis, ABC transporters, and hormone signaling. Pb measurements showed fungal inoculation restricted Pb uptake as a protective mechanism. M. anisopliae reshaped the soil bacterial community, enriching taxa associated with plant growth promotion and contaminant tolerance. These findings identify M. anisopliae seed inoculation as a strategy to mitigate Pb and NP phytotoxicity in rice by integrating contaminant uptake control with plant and rhizosphere reprogramming.