Polyamines Confer Salt Tolerance in Mung Bean (Vigna radiata L.) by Reducing Sodium Uptake, Improving Nutrient Homeostasis, Antioxidant Defense, and Methylglyoxal Detoxification Systems - PubMed (original) (raw)

Polyamines Confer Salt Tolerance in Mung Bean (Vigna radiata L.) by Reducing Sodium Uptake, Improving Nutrient Homeostasis, Antioxidant Defense, and Methylglyoxal Detoxification Systems

Kamrun Nahar et al. Front Plant Sci. 2016.

Abstract

The physiological roles of PAs (putrescine, spermidine, and spermine) were investigated for their ability to confer salt tolerance (200 mM NaCl, 48 h) in mung bean seedlings (Vigna radiata L. cv. BARI Mung-2). Salt stress resulted in Na toxicity, decreased K, Ca, Mg, and Zn contents in roots and shoots, and disrupted antioxidant defense system which caused oxidative damage as indicated by increased lipid peroxidation, H2O2 content, [Formula: see text] generation rate, and lipoxygenase activity. Salinity-induced methylglyoxal (MG) toxicity was also clearly evident. Salinity decreased leaf chlorophyll (chl) and relative water content (RWC). Supplementation of salt affected seedlings with exogenous PAs enhanced the contents of glutathione and ascorbate, increased activities of antioxidant enzymes (dehydroascorbate reductase, glutathione reductase, catalase, and glutathione peroxidase) and glyoxalase enzyme (glyoxalase II), which reduced salt-induced oxidative stress and MG toxicity, respectively. Exogenous PAs reduced cellular Na content and maintained nutrient homeostasis and modulated endogenous PAs levels in salt affected mung bean seedlings. The overall salt tolerance was reflected through improved tissue water and chl content, and better seedling growth.

Keywords: ROS signaling; abiotic stress; methylglyoxal; oxidative damage; polyamine; salinity.

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Figures

FIGURE 1

FIGURE 1

Effect of exogenous polyamines on Na uptake and nutrient homeostasis in mung bean seedlings under salt stress (NaCl, 200 mM). Root Na (A), shoot Na (B), root K (C), and shoot K (D) root Ca (E), shoot Ca (F), root Mg (G), shoot Mg (H), root Zn (I), and shoot Zn (J) contents. Here, Put, Spd, and Spm indicate putrescine (0.2 mM), spermidine (0.2 mM), and spermine (0.2 mM), respectively. Mean (±SD) was calculated from three replicates for each treatment. Bars with different letters are significantly different at P ≤ 0.05 applying Tukey’s HSD test.

FIGURE 2

FIGURE 2

Histochemical detection of ROS in leaves, content of ROS, LOX activity, and membrane lipid peroxidation in salt (NaCl, 200 mM) affected mung bean seedlings. DAB staining (A) of H2O2 and NBT staining (B) of O2•- in leaves, H2O2 content (C), O2•- generation rate (D), LOX activity (E), and MDA content (F). Here, Put, Spd, and Spm indicate putrescine (0.2 mM), spermidine (0.2 mM), and spermine (0.2 mM), respectively. Mean (±SD) was calculated from three replicates for each treatment. Bars with different letters are significantly different at P ≤ 0.05 applying Tukey’s HSD test.

FIGURE 3

FIGURE 3

Effect of exogenous polyamines on non-enzymatic antioxidants in mung bean seedlings under salt (NaCl, 200 mM) stress. Ascorbate (AsA) content (A), DHA content (B), AsA/DHA ratio (C), GSH content (D), GSSG content (E), and GSH/GSSG ratio (F). Here, Put, Spd, and Spm indicate putrescine (0.2 mM), spermidine (0.2 mM), and spermine (0.2 mM), respectively. Mean (±SD) was calculated from three replicates for each treatment. Bars with different letters are significantly different at P ≤ 0.05 applying Tukey’s HSD test.

FIGURE 4

FIGURE 4

Effect of exogenous polyamines on glyoxalase enzymes and in reducing MG toxicity in mung bean seedlings subjected to salt (NaCl, 200 mM) stress. Activity of Gly I (A), activity of Gly II (B), and MG content (C). Here, Put, Spd, and Spm indicate putrescine (0.2 mM), spermidine (0.2 mM), and spermine (0.2 mM), respectively. Mean (±SD) was calculated from three replicates for each treatment. Bars with different letters are significantly different at P ≤ 0.05 applying Tukey’s HSD test.

FIGURE 5

FIGURE 5

Endogenous levels of free polyamines in salt (NaCl, 200 mM) affected mung bean seedlings induced by treatment with exogenous polyamines. Endogenous Put (A), Spd (B), and Spm (C) contents and the ratio of (Spd+Spm)/Put (D). Here, Put, Spd, and Spm indicate exogenous putrescine (0.2 mM), spermidine (0.2 mM), and spermine (0.2 mM), respectively. Mean (±SD) was calculated from three replicates for each treatment. Bars with different letters are significantly different at P ≤ 0.05, applying Tukey’s HSD test.

FIGURE 6

FIGURE 6

Mechanism of PAs-induced salt stress tolerance. In glyoxalase system, HA indicates hemithioacetal and SLG indicates S-

D

-lactoylglutathione.

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