Identification and Characterization of Superoxide Dismutase in Lactuca sativa against Zinc Oxide and Titanium Dioxide Nanotoxicity

Abstract

Nanoparticles (NPs) have found their way into our daily lives and there is a need to critically evaluate the risks posed by such nanomaterils towards edible crops. Present study aimed to find out Zinc oxide (ZnO) and Titanium dioxide (TiO2) NPs induced phytotoxicity in Lettuce (lactuca sativa). The present study demonstrates that TiO2-NPs as well as ZnO-NPs are taken up by lettuce plants. TiO2 and ZnO translocation was confirmed by Scanning Electron Microscopy and X-Ray Diffraction. Expressed sequences tags of Superoxide Dismutases (SODs) in lettuce were identified and analysed phylogenetically after successful retrieval from three different databases, namely; Compositae genome project, DDBJ/EMBL/GenBank sequence database and GenomeNET. All the lettuce SODs, as a result of clustering within the tree, fell within three classes of Arabidopsis SODs namely; Cu/Zn-SOD, Mn-SOD, and Fe-SOD. Gene expression changes of SODs in lettuce plants were examined using quantitative real time PCR indicating that the SOD genes (Mn-SOD and Cu/Zn-SOD) responded similarly against ZnO and TiO2 nanotoxicity. Both SOD genes were induced in response to ZnO and TiO2 nanotoxicity. Fold change against ZnO was observed as 2.848, 3.608, and 3.85 and against TiO2 was 23, 17.66, and 3.45 in Cu/Zn-SOD1, Cu/Zn-SOD2, and Mn-SOD respectively. Effects of NPs on enzyme activity were also examined. The SOD activity (inhibition rate %) in control, ZnO, and TiO2 NPs treated lettuce plants was quantified as 43, 50, and 46% respectively