Bidirectional interference between nanoplastics and arsenic in arbuscular mycorrhizal symbiosis: Reciprocal modulation of uptake, transformation and translocation

Nanoplastics, which persist in the environment with high specific surface areas, interact with the well-documented pollutant arsenic, thereby exacerbating its phytotoxicity. Arbuscular mycorrhizal fungi, forming symbiotic relationships with most plants and enhancing their arsenic tolerance, possess hyphae capable of capturing nanoplastics. However, no studies have investigated either how arbuscular mycorrhizal fungi absorb and transfer arsenic during nanoplastics co-exposure, or whether nanoplastics are internalized by arbuscular mycorrhizal fungi hyphae and translocated to mycorrhizal tissues under arsenic stress. In this study, a two-compartment in vitro monoxenic cultivation system was used to investigate the synergistic translocation and transformation of arsenic-nanoplastic co-contaminants at the plant-microbe interface. The results indicated that nanoplastics hindered the arsenic absorption by arbuscular mycorrhizal fungi hyphae and promoted the transformation of inorganic arsenic to organic arsenic via upregulating the relative expression of the RiMT-11 gene in the hyphae. Scanning electron microscopy and confocal laser scanning microscopy imaging confirmed nanoplastics internalization by hyphae and subsequent translocation to mycorrhizae under arsenic exposure. This study deciphers nanoplastic-arsenic-arbuscular mycorrhizal fungi interaction mechanisms and validates arbuscular mycorrhizal fungi's potential role in the bioremediation of arsenic-nanoplastic co-contaminated soils.