Abstract
Glycine betaine is an osmoprotectant compound which enhances cell tolerance in plant species in response to environmental stresses. This study aimed to investigate the effect of exogenous application of glycine betaine on some antioxidant activities of tobacco plants overexpressing P5CS gene. Sterile tobacco seedlings with four to six leaves were transferred to MS medium containing 0, 100, and 200 mM NaCl, after which glycine betaine (20 and 40 mg l-1) were foliar sprayed on the surface of the plants. After four weeks, glycine betaine treatment enhanced the antioxidant capacity of the plant through activation of catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). In contrast, H2O2 content and MDA level were reduced by glycine betaine under similar conditions. Therefore, application of exogenous glycine betaine under salt stress improved stress tolerance in T and non-T plants. Meanwhile, our results indicated the positive effect of glycine betaine in T plants was greater than in non-T plants. On the other hand, this result suggested that the synergistic effects of glycine betaine and proline in plants enhanced the antioxidant defense system in T plants overexpressing P5CS gene.
Highlights
Salt stress is one of the most important factors, which limits and reduces the growth and development of plants worldwide
It was hypothesized that, increasing proline in transgenic tobacco plants and application of glycine betaine in the medium may offer positive effects on the response of tobacco plants under salinity stress? the present study investigated the protective effect of GB on the antioxidant defense systems of transgenic (T) tobacco plants overexpressing pyrroline5-carboxylate synthase (P5CS) gene to determine the relationship between osmoprotectant properties of GB and its antioxidant capacity under salt stress
Analysis of variance showed that salt, GB and plant effect were significant on H2O2 and MDA content (Table1)
Summary
Salt stress is one of the most important factors, which limits and reduces the growth and development of plants worldwide. It is known that accumulation of compatible osmolytes such as proline (Pro) and glycine betaine (GB) (Díaz et al, 2005) as well as reactive oxygen species (ROS) detoxification in plants increases salt tolerance. Drought, and heavy metal stresses induce generation of reactive oxygen species (ROS) such as superoxide and hydrogen peroxide (Rajaeian & Ehsanpour, 2015). The enzymatic antioxidants include superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). In this system, superoxide radical is converted to hydrogen peroxide (H2O2) by SOD enzyme (Bowler et al, 1992). H2O2 is converted to water by catalase and peroxidase enzymes (Fridovich, 1983)
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