From the rhizosphere to plant fitness: Implications of microplastics soil pollution

Microplastics (MPs) are a widespread contaminant in the terrestrial environment, with potential impacts on the soil-plant system not yet well understood. This study explores the effects of oxidised low-density polyethylene-MPs (LDPE-MPs) on the rhizosphere ecology and plant fitness of Fragaria x ananassa (Duchesne ex Weston) Duchesne ex Rozier. The rhizospheric microbial community was investigated under the influence of 0,5% LDPE-MPs by internal transcribed spacer (ITS) and 16 S rRNA metagenomic analysis; photosynthetic parameters, antioxidant enzyme activities, and nutrient accumulation were assessed to evaluate plant physiological and biochemical status. Genes related to jasmonic acid (JA), ethylene biosynthesis, and nitrate signalling pathways were analysed to define the plant molecular response. Our results showed a shift in the rhizosphere microbial community. We identified MPs molecular biomarkers in the contaminated rhizosphere (Fusarium, Thanatephorus and Pseudallescheria) with potential pathogenic functions and two novel molecular biomarkers (Ohtaekwangia and Ascobolus). MPs pollution negatively impacts plant fitness, which showed decreased chlorophyll a and b (40 and 48%, respectively), a change in nutrient content (fluctuations between 14,42 and 26,7%) at the leaf level and increased activity of antioxidant enzymes. Gene expression related to JA, ethylene biosynthesis, and nitrogen signalling pathways is enhanced in plants grown in contaminated soil, as well as the root endophytic and epiphytic microorganism interactions. Our results demonstrate that MPs pollution influences the rhizosphere microbial community and functions, and consequently, negatively impacts plant health.