Role of Antioxidant Enzymes and Glutathione S-Transferase in Bromoxynil Herbicide Stress Tolerance in Wheat Plants.

BACKGROUND: Numerous pesticides and herbicides used in excess cause oxidative stress in plants. These chemicals protect plants from weeds and pests, but they also have very negative side effects, making them common abiotic stressors. One of the most significant nutritional crops in the world is the wheat plant. Conditions of herbicide stress have a negative impact on the plant's phonological phases and metabolic pathways. Plants primarily make an effort to adjust to the environment and develop oxidative homeostasis, which supports stress tolerance. METHODS: When controlling broadleaf weeds that emerge after cereal crop plants have been planted, bromoxynil is frequently used as a selective-contact herbicide. This study looked at the effects of the cyanobacteria Arthrospira platensis and Nostoc muscorum aqueous extracts, tryptophan, and bromoxynil (Bh) alone or in combination on wheat plant growth parameters. Both tryptophan and cyanobacterial extract were used as chemical and natural safeners against Bh application. The antioxidant activity and transcriptome studies using qRT-PCR were assayed after 24, 48, 72, 96 h, and 15 days from Bh application in the vegetation stage of wheat plants (55 days old). RESULTS: In comparison with plants treated with Bh, wheat plants treated with cyanobacteria and tryptophan showed improvements in all growth parameters. Following application of Bh, wheat plants showed reduced glutathione content, as well as reduced antioxidant enzyme activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-s-transferase. The combination of different treatments and Bh caused alleviation of the harmful effect induced by Bh on the measured parameters. Additionally, the expression of glutathione synthase and glutathione peroxidase, in addition to those of three genes (Zeta, Tau, and Lambda) of the GST gene family, was significantly upregulated when using Bh alone or in combination with different treatments, particularly after 24 h of treatment. CONCLUSION: The current study suggests using cyanobacterial extracts, particularly the A. platensis extract, for the development of an antioxidant defense system against herbicide toxicity, which would improve the metabolic response of developed wheat plants.

Evaluating the responses of some wheat landraces and cultivars cultivated locally in Saudi Arabia to three sources of irrigation water

This study was aimed to investigate the response of some wheat (Triticum aestivum L.) landraces to three irrigation sources, freshwater (FW), well water (WW), and treated municipal wastewater (TMW), regarding the impact on growth, yield, and grains elements contents. The results showed that the various wheat landraces irrigated with treated wastewater were significantly taller (117.3 cm) with multi tillers (22 tiller plant-1), had maximum spikes per plant (2.6), and longer weighty spikes (14.5 cm & 12.1 g). Landraces L1(Burr), L2 (Baldy Burr), C7 (Yecora Rojo), had maximum tillers, L4 (Alssamaa Burr), L5 (Bahaal Burr), L7 (Yecora Rojo) had more spikes per plant and the longer weighty spikes were recorded in L5 Baldy Burr, L1(Burr), heavy spikes were reported in L5 (Bahaal Burr) and L1(Burr). Moreover, these landraces had the highest yield per plant and 1000 grains weight (49.8 g, 12.5 g) respectively. The N, P, K, and Mg contents were increased under TMW, and their levels in landraces and cultivars in order are 3>L2>L4>L5>L1>C6>C7. Even Cu, Fe, Mn, Zn levels were higher in various landraces irrigated with TMW, however, L3, L2, and L4 had maximum contents of all microelements. TMW irrigation enhanced growth, yield, and grain quality in terms of essential elements. The irrigation of landraces L1, L4, L5 with TMW may be a feasible alternative for sustainable wheat production and safe water in arid regions such as Saudi Arabia.

Hydrogen sulfide (H2S) and potassium (K+) synergistically induce drought stress tolerance through regulation of H+-ATPase activity, sugar metabolism, and antioxidative defense in tomato seedlings.

KEY MESSAGE: Exogenous potassium (K+) and endogenous hydrogen sulfide (H2S) synergistically alleviate drought stress through regulating H+-ATPase activity, sugar metabolism and redox homoeostasis in tomato seedlings. Present work evaluates the role of K+ in the regulation of endogenous H2S signaling in modulating the tolerance of tomato (Solanum lycopersicum L. Mill.) seedlings to drought stress. The findings reveal that exposure of seedlings to 15% (w/v) polyethylene glycol 8000 (PEG) led to a substantial decrease in leaf K+ content which was associated with reduced H+-ATPase activity. Treatment with sodium orthovanadate (SOV, PM H+-ATPase inhibitor) and tetraethylammonium chloride (TEA, K+ channel blocker) suggests that exogenous K+ stimulated H+-ATPase activity that further regulated endogenous K+ content in tomato seedlings subjected to drought stress. Moreover, reduction in H+-ATPase activity by hypotaurine (HT; H2S scavenger) substantiates the role of endogenous H2S in the regulation of H+-ATPase activity. Elevation in endogenous K+ content enhanced the biosynthesis of H2S through enhancing the synthesis of cysteine, the H2S precursor. Synergistic action of H2S and K+ effectively neutralized drought stress by regulating sugar metabolism and redox homoeostasis that resulted in osmotic adjustment, as witnessed by reduced water loss, and improved hydration level of the stressed seedlings. The integrative role of endogenous H2S in K+ homeostasis was validated using HT and TEA which weakened the protection against drought stress induced impairments. In conclusion, exogenous K+ and endogenous H2S regulate H+-ATPase activity which plays a decisive role in the maintenance of endogenous K+ homeostasis. Thus, present work reveals that K+ and H2S crosstalk is essential for modulation of drought stress tolerance in tomato seedlings.