Effect of Fe3O4 and CuO Nanoparticles on Morphology, Genotoxicity, and miRNA Expression on Different Barley (Hordeum vulgare L.) Genotypes.

Metal nanoparticles (NPs) have an influence on plant growth and development. They can alter plant shoot and root length, fresh biomass production, and even influence the genome. Nanoparticles are also able to affect expression levels of plant microRNAs. MicroRNAs are able to protect plants from biotic stress, including pathogens which cause powdery mildew. In this study, Hordeum vulgare L. varieties "Marthe" and "KWS Olof" were grown in hydroponics with magnetic iron oxide (Fe3O4) and copper oxide (CuO) NPs added at 17, 35, and 70 mg/L. Plant morphology, genotoxicity, and expression of miR156a were investigated. The Fe3O4 and CuO NPs demonstrated different effects on the barley varieties, namely, Fe3O4 nanoparticles increased plant shoot and root lengths and fresh biomass, while CuO nanoparticles decreased them. CuO NPs presence caused larger changes on barley genome compared to Fe3O4 NPs. Thus, Fe3O4 NPs reduced genome stability to 72% in the "Marthe" variety and to 76.34% in the "KWS Olof" variety, while CuO NPs reduced genome stability to 53.33% in "Marthe" variety and in the "KWS Olof" variety to 68.81%. The miR156a expression levels after Fe3O4 NPs treatment did not change in the "Marthe" variety, but increased in the "KWS Olof" variety, while CuO NPs treatment increased miRNA expression levels in the "Marthe" variety but decrease them in the "KWS Olof" variety. As NPs are able to influence miRNA expression and miRNAs can affect the plant resistance, obtained results suggest that tested NPs may alter plant resistance response to pathogens.