Effect of Zinc Heavy Metal on Stress-Related Genes in Tomato (Solanumlycopericum L.) Plants

Heavy metal pollution is a major environmental problem all over the world. It is known that high concentration of heavy metals in soils and waters cause genotoxicity and damage to most of the functional biomolecules. The aim of this study was to determine the molecular changes in tomato (Solanumlycopericum L.) genome under heavy metal of zinc stress.Zinc is a microelement which should be taken in very less amounts by plants, animals and humans. In plants, zinc in low concentration is essential for root and stem elongation, RNA levels, the cell's ribosome content and protein formation mechanism. But at high concentrations, it is toxic for plants like cadmium, lead and copper.In this current study, the molecular response of tomato (Solanumlycopericum L.) plants to zinc stress was examined by transcript accumulation analysis of two stress-related genes: (i) MT2 (metallothionein) gene, coding for a metal-binding protein and (ii) GR1 (glutathionreductase) gene, a marker of enzymatic ROS scavenging mechanism. A quantitative Real-Time PCR experiment was performed with MT2 and GR1 genes using RNA isolated from tomato roots or shoots treated for 24h with zinc at concentrations ranging from 20 to 1280ppm. Results showed that the genes were over-expressed in zinc-stressed tomato. The highest relative fold change value was measured on GR1 for both root and shoot indicating the activation of the oxidative stress enzyme to tolerate zinc stress.