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

Farmers use plastic mulching films to suppress weeds and protect plants from biotic and abiotic stresses; however, these films can become a source of microplastics in ecosystems. To better understand how plastic film-derived microplastics influence the rhizosphere microbiome and plant health, we examined the effects of plastic residues on Arabidopsis thaliana grown in treated soils. Plastic residues (≥5 mm) were mixed with agricultural soils at 5% (w/w) and incubated at 25 °C and 80% relative humidity in the dark for 120 d to allow microbial community stabilization. Neither the presence of plastics, soil incubation, nor their interaction significantly affected seedling growth or flowering time. However, rhizobacterial compositions were significantly changed by plastic treatment, incubation, and their interaction, despite no change in the α-diversity within each bacterial community tested in this study. Notably, the abundance of bacterial families, such as Alcanivoracaceae, Cytophagaceae, and Latescibacteraceae, shifted in response to plastic. Additionally, changes in the microbiome and treatment conditions induced transcriptional alterations in genes involved in photosynthesis, nitrogen assimilation, and the response to oxidative stress. These findings suggest that plastic residues in soil indirectly affect the bacterial community and plant gene expression; thus, their interaction should be considered to maintain sustainable agroecosystems.