Identification and Characterization of Glutathione S-transferase against Zinc Oxide and Titanium Dioxide Nanotoxicity in Lactuca sativa

Abstract

Zinc oxide (ZnO) and Titanium dioxide(TiO2) nanoparticles (NPs) are released into the environment and pose serious risks to plants. Impact of these NPs on edible food crops, which is a point of entry of NPs into the food chain, is very little documented. In the present study, we aimed to identify Glutathione S transferase (GST) genes from Lactuca sativa (lettuce) genome and check their response against nanotoxicity imposed by ZnO and TiO2 NPs. Translocation of the NPs in lettuce was confirmed through X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis. In silico analysis revealed the presence of 113 putative GST genes in lettuce from Compositae genome project database, GenomeNET and DDBJ/EMBL/GenBank sequence database; that were divided into 5 classes through phylogenetic analysis. Quantitative real time PCR was used to monitor the changes in expression ofTC18793 gene of phi class, TC20111 and TC20660 genes of tau class in ZnO and TiO2 treated plants. Expression of TC18793, TC20111 and TC20660 genes was upregulated by 39.2, 4.7 and 5.7 fold respectively in ZnO NP treated plants while TC18793, TC20111 and TC20660 genes was upregulated by 0.79, 17.90 and 0.94 fold in TiO2 NP treated plants. GST specific enzyme activity was also significantly increased (p<0.05) in ZnO and TiO2 treated plants. Our results indicate that TiO2.and ZnO NPs may cause the phytotoxicity in lettuce.