Synergistic response of arbuscular mycorrhizal fungi and hyphosphere microbiome to arsenic contamination in agricultural soils

Arbuscular mycorrhizal fungi (AMF) can modulate arsenic (As) bioavailability through hyphal interactions with microbes. However, whether AMF hyphae assemble a core hyphosphere microbiome adapted to As stress and how this shapes in situ As transformation are still unknown. We conducted field experiments across agricultural soils with an As gradient (21-172 mg kg^-1), using in situ mesh devices to collect hyphosphere and nonhyphosphere soils during a 98-d wheat growth period. We integrated 16S rRNA and ITS gene sequencing, PICRUSt2-based functional prediction, co-inertia and co-occurrence analyses, and sequential As extraction to investigate the hyphosphere microbiome's structure, functional potential, and AMF-microbe interactions. AMF hyphae significantly increased microbial diversity and niche breadth in the hyphosphere and reshaped community composition. Co-inertia and network analyses showed stronger associations under high As stress. We identified 100 ASVs as a core hyphosphere microbiome - dominated by Proteobacteria, Bacteroidetes, and Verrucomicrobia - rich in arsC, arsH, and arsB/ACR3 genes. Network modules formed by these taxa correlated positively with bioavailable As, suggesting adaptive potential under stress. This study provides the first field-based evidence that AMF hyphae selectively recruit a core microbiome with potential As-transforming functions, offering microbial targets for AMF-assisted remediation of As-contaminated soils.