Investigation of antioxidant genes and some biochemical traits of bread wheat under mercury metal stress

Mercury, as a heavy metal element, plays an important role in contaminating the environment and causing toxicity and stress in living organisms. . Heavy metals are defined as metals having an atomic number greater than 20 densities greater than 5 grams per cubic centimeter.Non-toxic stresses, including heavy metals, cause much damage to wheat. The industrialization of societies is releasing many toxic compounds on the biosphere. Among heavy metals, mercury is considered to be the most toxic metal in the environment. This metal is considered as the major environmental pollutant. Its toxicity is a big problem for ecological, evolutionary, nutritional and environmental reasons. In fact, heavy metals do not excrete the body after entering the body and accumulate in the tissues of the body. Despite the contamination of resources used in heavy metals, while reducing the quantity and quality of agricultural products, sustainable production and human health are also at risk. The same causes many diseases and complications in the body, the pollution of the environment with heavy elements will transfer them to crops, which is now spreading as a global problem.Mercury ions produce oxidative stress that produces reactive oxygen species in plants. This pro cess damages the structure of the membranes and disrupts the cytoplasm of the cell. To reduce and eliminate various active oxygen species and avoid oxidative damage in plants, the activity of antioxidant enzymes such as catalase increases. One of the other mechanisms of coping with heavy metal stresses in living cultures is the production of intracellular, rich in cysteine amino acids such as metallothionein. The high number and special makeup of cysteine amino acids in these proteins has made it possible to connect them to metals.

A split plot experiment was conducted in a completely randomized design with hydroponic culture. The treatments consisted of chloride ivy with concentrations (0, control, 5, 10 and 15 μm) as the main factor and bread wheat genotypes (morvared, gonbad and N9108) as a sub factor.

Results showed that the expression of catalase and metallothionein gene was increased in morvared and N9108 genotypes by mercury chloride and the highest expression of these genes was obtained by treatment with 15 mM mercuric chloride (9.2 and 2.7 times more than control) Was. In Gonbad cultivar, the amount of gene expression was increased by treatment with mercury chloride compared to control, but this increase was lower than the other two genotypes. By increasing the concentration of mercury chloride, there was a significant decrease in the chlorophyll content of different genotypes, as well as chloride ivy significantly increased the oxidative cell index in the treated seedlings compared with the control It can be concluded that the morvared cultivar and the promising line of N9108 under heavy metal stress showed a better response than the gonbad. Used to deal with heavy metal stresses. According to the results of this experiment, it seems that the antioxidant defense system plays an important role in the defense strategy of the wheat plant against the tension of mercury metal and this defense system is induced and activated at the transcriptional level to help the plant.