Alleviation of isoproturon toxicity to wheat by exogenous application of glutathione

Remediation of isoproturon-contaminated soil by Sphingobium sp. strain YBL2: Bioaugmentation, detoxification and community structure

The widely used phenylurea herbicide isoproturon (IPU) and its residues can inhibit the growth of subsequently planted crops. However, reports on bioremediation of IPU-contaminated soil are scarce. In this study, Sphingobium sp. strain YBL2-gfp (a derivative of the IPU-degrading Sphingobium sp. strain YBL2 isolated by our lab) was constructed to bioremediate IPU-contaminated soil. In pot experiments, strain YBL2-gfp colonized the roots of wheat and eliminated IPU residues in the soil within 21 d, effectively alleviating its toxicity and restoring wheat growth. IPU treatment reduced the richness and diversity of soil bacteria, while inoculation YBL2-gfp mainly affected richness with less impact on diversity. The high concentrations of IPU and inoculation of YBL2-gfp alone reduced the soil microbial community connections, while bioaugmentation treatment enhanced the soil microbial community connections. Additionally, strain YBL2-gfp stimulated the metabolic capacity of the indigenous microbes, promoting the degradation of IPU and reducing the negative impact of high concentrations of IPU on microbial community. Taken together, this study offers relatively comprehensive insights into the practical application of bioaugmentation, demonstrating that strain YBL2 has the potential to remediate IPU-contaminated soils.

Exogenous glutathione maintains the postharvest quality of mango fruit by modulating the ascorbate-glutathione cycle

Background

Mango fruit is prone to decay after harvest and premature senescence, which significantly lowers its quality and commercial value.

Methods

The mango fruit (Mangifera indica L.cv. Guixiang) was treated with 0 (control), 2, 5, and 8 mM of reduced glutathione (GSH) after harvest. The fruit was stored at 25 ± 1 °C for 12 days to observe the changes in the antioxidant capacity and postharvest quality.

Results

Compared with the control, the 5 mM GSH treatment significantly decreased the weight loss by 44.0% and 24.4%, total soluble solids content by 25.1% and 4.5%, and soluble sugar content by 19.0% and 27.0%. Conversely, the 5 mM GSH treatment increased the firmness by 25.9% and 30.7% on days 4 and 8, respectively, and the titratable acidity content by 115.1% on day 8. Additionally, the 5 mM GSH treatment decreased the malondialdehyde and hydrogen peroxide contents and improved the antioxidant capacity of mango fruit by increasing the superoxide dismutase and peroxidase activities and upregulating the expression of the encoding genes. Meanwhile, the higher levels of monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase enzyme activities and gene expressions accelerated the AsA-GSH cycle, thereby increasing the accumulation of AsA and GSH and maintaining the redox balance.

Conclusions

Overall, the experimental results suggest that 5 mM GSH maintains high antioxidant capacity and postharvest quality of mangoes and can use as an effective preservation technique for postharvest mangoes.

Antioxidant Potential of Glutathione and Crosstalk with Phytohormones in Enhancing Abiotic Stress Tolerance in Crop Plants

Glutathione (GSH) is an abundant tripeptide that can enhance plant tolerance to biotic and abiotic stress. Its main role is to counter free radicals and detoxify reactive oxygen species (ROS) generated in cells under unfavorable conditions. Moreover, along with other second messengers (such as ROS, calcium, nitric oxide, cyclic nucleotides, etc.), GSH also acts as a cellular signal involved in stress signal pathways in plants, directly or along with the glutaredoxin and thioredoxin systems. While associated biochemical activities and roles in cellular stress response have been widely presented, the relationship between phytohormones and GSH has received comparatively less attention. This review, after presenting glutathione as part of plants' feedback to main abiotic stress factors, focuses on the interaction between GSH and phytohormones, and their roles in the modulation of the acclimatation and tolerance to abiotic stress in crops plants.

Effect of Pyrazosulfuron-Methyl on the Photosynthetic Characteristics and Antioxidant Systems of Foxtail Millet

Foxtail millet (Setaria Italica L.) plays a principal role in food security in Africa and Asia, but it is sensitive to a variety of herbicides. This study was performed to clarify whether pyrazosulfuron-methyl can be used in foxtail millet fields and the effect of pyrazosulfuron-methyl on the photosynthetic performance of foxtail millet. Two foxtail millet varieties (Jingu 21 and Zhangzagu 10) were subjected to five doses (0, 15, 30, 60, and 120 g ai ha-1) of pyrazosulfuron-methyl in pot and field experiments. The plant height, leaf area, stem diameter, photosynthetic pigment contents, gas exchange parameters, chlorophyll fluorescence parameters, antioxidant enzyme activities, and antioxidant contents at 7 and 15 days after pyrazosulfuron-methyl application, and the yield of foxtail millet were measured. The results suggested that pyrazosulfuron-methyl inhibited the growth of foxtail millet and reduced the photosynthetic pigment contents, photosynthetic rate, and photosynthetic system II activity. Similarly, pyrazosulfuron-methyl decreased the antioxidant enzyme activities and antioxidant contents. These results also indicated that the toxicity of pyrazosulfuron-methyl to foxtail millet was decreased gradually with the extension of time after application; however, the foxtail millet yield was still significantly reduced. Therefore, pyrazosulfuron-methyl is not recommended for application in foxtail millet fields.

Naphthalic anhydride decreases persistence of alachlor and atrazine and elevates tolerance of maize

The present study aimed at alleviating the impacts of alachlor (Ala) or atrazine (Atr) on maize growth by seed-dressing with naphthalic anhydride (NA, 0.4% w/w by seed weight). The dressed and undressed seeds were germinated for 10 days and treated with Ala or Atr at 3.2 or 1.8 kg ha^-1, respectively, then the herbicide residues were determined in shoots one day after treatment. Atr residues were higher than Ala and remained in the same level for the 2^nd day then retracted consistently up to 12 days. Meanwhile, GSH and GST were significantly induced while growth parameters were reduced; the effect of Atr was higher than Ala. Nonetheless, ABA, phenolics and anthocyanins as well as PAL, TAL and CI were increased but IAA was decreased coincidently with enhanced IAA-O and peroxidase. The immediate detection of the herbicide residues could conclude that growth reduction as elucidated from the decreased IAA concomitant with elevating ABA, phenolics and anthocyanin contents and enzyme activities are consequences of the herbicide persistence. The drop of IAA was preceded by the stimulation of IAA-O and peroxidase while the increased phenolics and anthocyanins followed PAL, TAL and CI stimulation confirming the regulatory roles of these enzymes. The application of NA greatly lowered the herbicide residues concurrently with ameliorations in growth parameters, GSH, GST, and maintained the balancing of secondary metabolites and plant growth regulators. Lowering Ala and Atr residues by NA in synchronization with enhanced GSH and GST could conclude that NA encouraged the detoxification of the herbicide. Moreover, the balances of IAA, ABA, phenolics and anthocyanins were mostly maintained in normal levels concomitantly with growth ameliorations suggesting that phytohormones and secondary metabolites are involved in the elevation of maize tolerance to Ala and Atr.

Phytotoxicity assessment of isoproturon on growth and physiology of non-targeted aquatic plant Lemna minor L. - A comparison of continuous and pulsed exposure with equivalent time-averaged concentrations

Phenylurea herbicides are often present in the aquatic ecosystems and may be accumulated by the non-targeted organisms and impose a negative effect on the organism and the community. This study aims to investigate and compare the effects of two different isoproturon (IPU) pulse exposure scenarios on the non-targeted aquatic plant Lemna minor with effects observed in the standard test with continuous exposure. The obtained results showed that continuous IPU treatment causes significant reduction of photosynthetic pigment concentration and proteins as well as inhibition of L. minor growth. The activities of CAT, G-POX, and APX were significantly induced to diminish the accumulation of ROS under IPU treatment, but the induction of antioxidant enzymes was not sufficient to protect the plants from herbicide-induced oxidative stress. The growth of L. minor under pulse exposure to IPU recovers fast, but pulse treatment results in significant physiological changes in treated plants. The accumulation of H₂O₂ and lipid peroxidation products, alongside the reduced concentration of proteins and photosynthetic pigments in pulse treatment after a recovery period, indicates that IPU causes prolonged oxidative stress in L. minor plants. The recovery potential of L. minor plants after treatment with herbicides may have an important role in maintaining the population of essential primary producers in aquatic ecosystems, but IPU-induced physiological changes could potentially have a significant role in modulating the response of the plants to the next exposure event.

Elimination of the Effect of Some Herbicides on the Growth of Zea mays and Accumulation in the Soil Using Urea

ABSTRACT: This study evaluates the effect of urea on growth of herbicide-treated maize and its accumulation in the soil. When the seedlings were 15 days old, the plots were divided into five groups. One group served as control, two received treatments with metolachlor and isoproturon at the dose of 1.5 kg ha-1 and 2.5 L ha-1, respectively. The two remaining groups received the same dose of herbicide along with urea added at a rate of 129 kg ha-1. The application of the two herbicides appeared to cause a significant decrease in shoot dry weight, photosynthetic pigments, d-aminolevulinate dehydratase enzyme [ALA-D, EC 4.2.1.24] and total soluble carbohydrates of the maize plants. The application of urea appeared to alleviate the effects of both herbicides on maize growth. A statistical analysis demonstrated a significant association between the soil criteria and the accumulation of herbicides in it. This study clearly highlights the urgent need for use of urea to retract the effects of herbicides on maize growth.

Reduced Glutathione Mediates Pheno-Ultrastructure, Kinome and Transportome in Chromium-Induced Brassica napus L

Chromium (Cr) as a toxic metal is widely used for commercial purposes and its residues have become a potential environmental threat to both human and plant health. Oilseed rape (Brassica napus L.) is one of the candidate plants that can absorb the considerable quantity of toxic metals from the soil. Here, we used two cultivars of B. napus cvs. ZS 758 (metal-tolerant) and Zheda 622 (metal-susceptible) to investigate the phenological attributes, cell ultrastructure, protein kinases (PKs) and molecular transporters (MTs) under the combined treatments of Cr stress and reduced glutathione (GSH). Seeds of these cultivars were grown in vitro at different treatments i.e., 0, 400 μM Cr, and 400 μM Cr + 1 mM GSH in control growth chamber for 6 days. Results had confirmed that Cr significantly reduced the plant length, stem and root, and fresh biomass such as leaf, stem and root. Cr noticeably caused the damages in leaf mesophyll cells. Exogenous application of GSH significantly recovered both phenological and cell structural damages in two cultivars under Cr stress. For the PKs, transcriptomic data advocated that Cr stress alone significantly increased the gene expressions of BnaA08g16610D, BnaCnng19320D, and BnaA08g00390D over that seen in controls (Ck). These genes encoded both nucleic acid and transition metal ion binding proteins, and protein kinase activity (PKA) and phosphotransferase activities in both cultivars. Similarly, the presence of Cr revealed elite MT genes [BnaA04g26560D, BnaA02g28130D, and BnaA02g01980D (novel)] that were responsible for water transmembrane transporter activity. However, GSH in combination with Cr stress significantly up-regulated the genes for PKs [such as BnaCnng69940D (novel) and BnaC08g49360D] that were related to PKA, signal transduction, and oxidoreductase activities. For MTs, BnaC01g29930D and BnaA07g14320D were responsible for secondary active transmembrane transporter and protein transporter activities that were expressed more in GSH treatment than either Ck or Cr-treated cells. In general, it can be concluded that cultivar ZS 758 is more tolerant toward Cr-induced stress than Zheda 622.

Exogenous glutathione improves high root-zone temperature tolerance by modulating photosynthesis, antioxidant and osmolytes systems in cucumber seedlings

To investigate the physiological responses of plants to high root-zone temperature (HT, 35 °C) stress mitigated by exogenous glutathione (GSH), cucumber (Cucumis sativus L.) seedlings were exposed to HT with or without GSH treatment for 4 days and following with 4 days of recovery. Plant physiological variables, growth, and gene expression related to antioxidant enzymes and Calvin cycle were quantified. The results showed that HT significantly decreased GSH content, the ratio of reduced to oxidized glutathione (GSH/GSSG), chlorophyll content, photosynthesis and related gene expression, shoot height, stem diameter, as well as dry weight. The exogenous GSH treatment clearly lessened the HT stress by increasing the above variables. Meanwhile, HT significantly increased soluble protein content, proline and malondialdehyde (MDA) content as well as O₂•⁻ production rate, the gene expression and activities of antioxidant enzymes. The GSH treatment remarkably improved soluble protein content, proline content, antioxidant enzymes activities, and antioxidant enzymes related gene expression, and reduced the MDA content and O₂•⁻ production rate compared to no GSH treatment in the HT condition. Our results suggest that exogenous GSH enhances cucumber seedling tolerance of HT stress by modulating the photosynthesis, antioxidant and osmolytes systems to improve physiological adaptation.

Phaseolus vulgaris L. Seedlings Exposed to Prometryn Herbicide Contaminated Soil Trigger an Oxidative Stress Response

Herbicides from the family of S-triazines, such as prometryn, have been widely used in crop production and can constitute an environmental pollution in both water and soil. As a valuable crop, the common bean (Phaseolus vulgaris L.) is grown all over the world and could be exposed to such herbicides. We wanted to investigate the possible stress sustained by the common bean growing in prometryn-polluted soil. Two situations were observed: when soil was treated with ≥100 μM prometryn, some, but not all, measured growth parameters were affected in a dose-dependent manner. Growth was reduced, and photosynthetic pigments and photosynthetic products were less accumulated when soil was treated with ≥100 μM prometryn. Reactive oxygen species (ROS) produced had a deleterious effect, as seen by the accumulation of oxidized lipid in the form of malondialdehyde (MDA). Higher prometryn (500 μM) concentrations had a disastrous effect, reducing antioxidant activities. At a low (10 μM) concentration, prometryn increased antioxidant enzymatic activities without affecting plant growth or MDA production. Gene expression of proline metabolism genes and proline accumulation confirm that bean plants respond to a stress according to the prometryn concentration. Physiological responses such as antioxidative enzymes APX, CAT, and the enzyme implicated in the metabolization of xenobiotics, GST, were increased at 10 and 100 μM, which indicated a prevention of deleterious effects of prometryn, suggesting that bean is a suitable material both for herbicide pollution sensing and as a crop on a low level of herbicide pollution.