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

Abstract

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 ( Solanum lycopericum 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 (Solanum lycopericum 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.

Expression analysis of Some Stress-Related Genes Induced by Cadmium on Tomato (Solanum lycopersicum L.) Plants

“…Metallothionein binding proteins (MTs) protect plants from metal stress and toxicity. Numerous studies have shown that MTs are highly expressed in many plants exposed to heavy metal toxicity [7,8,27]. Cysteine residue has the ability to bind heavy metals both physiologically (such as zinc, copper, and selenium) and xenobiotically (such as cadmium, mercury, silver, and arsenic) via thiol groups.…”

“…It plays a critical role in the defense system against ROS, which occurs as a result of stress factors, by maintaining the GSH level and acts as a substrate for glutathione-Stransferases. In many recent studies, it was stated that GR-1 expression increased against cadmium stress in various plants [7,9,[31][32][33][34][35].…”

“…This also shows that; it is the ineffectiveness of the resistance mechanism against cadmium stress in both roots and shoots after the specified concentrations. It was determined that the GR pathway was inhibited due to possible cellular damage and it could not provide protection against cadmium stress by using the stress recovery pathway [7,[31][32][33][34].…”

“…This causes changes in the expression of some genes that play a role in dealing with stress caused by heavy metal pollution. This change in gene expression allows plants to cope with stress [3,7,[22][23][24].…”

“…avy metal pollution, one of the most important environmental pollutants, is reported to accumulate in soil and water at high concentration, causing genotoxicity and damage to many functional biomolecules in living things. Heavy metals, which accumulate intensely in soil and water ecosystems, can be included in the food chain, especially by means of plant-based nutrients [6,7]. Thus, the heavy metals included in the food chain, may deteriorate the structure of many biomolecules such as proteins, enzymes and especially nucleic acids [8][9][10][11].…”