Agri-plastics in soils drive changes in the rhizosphere bacterial community and plant transcriptome in Arabidopsis

Farmers use low-density polyethylene plastic mulching films to suppress weeds and protect plants from biotic and abiotic stresses; however, these films are a source of microplastics in ecosystems. Understanding the effect of film-derived microplastics on the rhizosphere microbiome and plant growth and development is therefore crucial. Here, we investigated how plastic residues in soils affect the interaction between the rhizosphere microbiome and Arabidopsis ( Arabidopsis thaliana). To this end, we prepared plastic residues (≥5 mm), mixed them with agricultural field soils (5%, w/w), and incubated the mixed soils at 25°C and 80% relative humidity in the dark for 120 days to allow stabilization of the microbial community at the laboratory scale. The two independent variables (the presence of plastics and soil incubation) and their interaction did not affect seedling growth or flowering time. Bacterial taxon compositions in the rhizosphere were significantly changed by plastic treatment, soil incubation, and their interaction, although the evenness, richness, and diversity within each bacterial community remained unchanged. Notably, population sizes of bacterial families, such as Alcanivoracaceae, Cytophagaceae, and Latescibacteraceae, in the rhizosphere were altered by the presence of plastic. Additionally, the two independent variables and variation in the rhizomicrobiome induced changes in the transcription patterns of genes involved in photosynthesis, nitrogen assimilation, and the response to oxidative stress, suggesting that plastic residues influence microbial and plant activity. These findings suggest that plastic residues in soil indirectly affect the bacterial community and plant physiology; thus, their interaction should be considered in efforts to maintain sustainable agroecosystems.