Titanium Dioxide Nanoparticles Affect the Percentage of Free Radical Scavenging, Protein Content and DNA Mismatch Repair Genes in Zea mays L. and Triticum aestivum L.

This paper identifies the potential molecular markers predicting the impact of nTiO(2) on plants and explores the new statistical correlations between the biomarkers and growth parameters. The quantitative mRNA expression of the three genes involved in DNA mismatch repair (MLH1) and cell division (PCNA1 and PCNA2) in Zea mays and Triticum aestivum seedlings were related to the growth parameters measured in response to five nTiO(2) treatments. The results indicated that the higher concentrations were harmless to Z. mays but not to T. aestivum. nTiO(2) treatments increased the total protein levels in both species and significantly inhibited the percentage of DPPH radical scavenging in Z. mays compared with T. aestivum seedlings. The exposure to both 50 mu g/ml and 30 mu g/ml concentrations of nTiO(2) significantly induced the expression of MLH1 and PCNA1 genes in both species; however, the exposure to 30 mu g/ml of nTiO(2) also significantly induced the expression of PCNA2 genes in T. aestivum. The exposure to 50, 70 and 140 mu g/ml significantly inhibited the expression of PCNA2 in both species, while 70 and 140 mu g/ml repressed the expression of MLH1 and PCNA1 in the seedlings of Z. mays. The induction and repression of the expression of the three genes were correlated with some growth parameters and biological indices in both species. This key finding suggests that the above genes may play a vital role in mediating plant stress response to nTiO(2) and could be used as sensitive molecular biomarkers indicative of the oxidative stress of nTiO(2) exposure.