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Book Chapter
Abuelsoud, Walid, and Papenbrock J. Hirschmann, F. "Sulfur Metabolism and Drought Stress Tolerance in Plants." In Drought Stress Tolerance in Plants: Physiology and Biochemistry, 227-249. Vol. 1. Springer, 2016. Abstract

Complex processes on all levels, transcripts, proteins, and metabolites are involved in drought stress tolerance, but different from species to species. Recent evidences lead to the assumption that sulfur not only acts like other macronutrients, such as nitrate and phosphate, but that an increasing demand for sulfate during metabolic adaptation reactions to drought stress reflects specific roles of sulfur-containing compounds. The biosynthesis of osmolytes and osmoprotectants, such as choline-O-sulfate and polyamines, is increased, the levels of the main antioxidant, the tripeptide glutathione, and its precursor cysteine are elevated, and 3′-phosphoadenosine-5′-phosphate (PAP), produced in secondary sulfur assimilation as a byproduct in sulfation reactions from 3′-phosphoadenosine-5′-phosphosulfate (PAPS), was recently suggested to act in retrograde signaling in drought. Data available on the protection against abiotic stress is summarized and discussed, in particular, the compartment-specific importance of glutathione in connection with the subcellular accumulation of ROS during drought stress. There is evidence that a significant coregulation of sulfur metabolism and the biosynthesis of the drought hormone abscisic acid (ABA) operates to ensure sufficient cysteine availability for aldehyde oxidase maturation. In addition, the role of glucosinolates (Gls) in drought stress will be delineated, as the drought induced accumulation of aliphatic Gl is related to ABA formation whereas indole and aromatic Gl decreased during drought stress, suggesting that these Gls are not involved in the plants’ response to drought.

Journal Article
El-Soud, Walid Abu, Momtaz Mohamed Hegab, Hamada AbdElgawad, Gaurav Zinta, and Han Asard. "Ability of Ellagic Acid to Alleviate Osmotic Stress on Chickpea seedlings." Plant Physiology and Biochemistry (2013): -. AbstractWebsite

Abstract Seed germination and growth of seedlings are critical phases of plant life that are adversely affected by various environmental cues. Water availability is one of the main factors that limit the productivity of many crops. This study was conducted to assess the changes in the sensitivity of chickpea seedlings to osmotic stress by prior treatment of chickpea seeds with a low concentration (50 ppm) of ellagic acid. Ellagic acid was isolated and purified from Padina boryana Thivy by chromatographic techniques. After ellagic acid treatment, seeds were germinated for 10 days under different osmotic potentials (0, -0.2, -0.4, -0.6 and -0.8 MPa) of polyethylene glycol (PEG) solutions. Ellagic acid treatment accelerated the germination and seedling growth of chickpea under osmotic stress conditions. Consistent with the accelerated growth, ellagic acid treated seedlings also showed a significant increase in the total antioxidant capacity (FRAP) as well as an increase in the compatible solutes (proline and glycine betaine) content. Additionally, treated seedlings revealed lower lipid peroxidation levels (MDA), electrolyte leakage (EL) and H2O2. Flavonoid and reduced glutathione (GSH) content, and the activity of antioxidant enzymes [catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), glutathione reductase (GR)] and enzymes of the shikimic acid pathway [phenylalanine ammonia lyase (PAL) and chalcone synthase (CHS)] all showed a remarkable increase with ellagic acid pretreatment compared to untreated seedlings especially under mild osmotic stress values (-0.2 and -0.4 MPa). These results suggested that treatment with ellagic acid could confer an increased tolerance of chickpea seedlings to osmotic stress, through reducing levels of \{H2O2\} and increasing antioxidant capacity.

AbdElgawad, Hamada, Gaurav Zinta, Walid Abuelsoud, Yasser M. Hassan, DalalHussien M. Alkhalifah, Wael N. Hozzein, Rafat Zrieq, Gerrit T. S. Beemster, and Sébastjen Schoenaers. "An actinomycete strain of Nocardiopsis lucentensis reduces arsenic toxicity in barley and maize." 417 (2021): 126055. AbstractWebsite

Accumulation of arsenic in plant tissues poses a substantial threat to global crop yields. The use of plant growth-promoting bacterial strains to mitigate heavy metal toxicity has been illustrated before. However, its potential to reduce plant arsenic uptake and toxicity has not been investigated to date. Here, we describe the identification and characterization of a Nocardiopsis lucentensis strain isolated from heavy metal contaminated soil. Inoculation with this bioactive actinomycete strain decreased arsenic root and shoot bioaccumulation in both C3 and C4 crop species namely barley and maize. Upon arsenate treatment, N. lucentensis S5 stimulated root citric acid production and the plant’s innate detoxification capacity in a species-specific manner. In addition, this specific strain promoted biomass gain, despite substantial tissue arsenic levels. Detoxification (metallothionein, phytochelatin, glutathione-S-transferase levels) was upregulated in arsenate-exposed shoot and roots, and this response was further enhanced upon S5 supplementation, particularly in barley and maize roots. Compared to barley, maize plants were more tolerant to arsenate-induced oxidative stress (less H2O2 and lipid peroxidation levels). However, barley plants invested more in antioxidative capacity induction (ascorbate-glutathione turnover) to mitigate arsenic oxidative stress, which was strongly enhanced by S5. We quantify and mechanistically discuss the physiological and biochemical basis of N. lucentensis-mediated plant biomass recovery on arsenate polluted soils. Our findings substantiate the potential applicability of a bactoremediation strategy to mitigate arsenic-induced yield loss in crops.

AbdElgawad, Hamada, Walid Abuelsoud, Mahmoud M. Y. Madany, Samy Selim, Gaurav Zinta, Ahmed S. M. Mousa, and Wael N. Hozzein. "Actinomycetes Enrich Soil Rhizosphere and Improve Seed Quality as well as Productivity of Legumes by Boosting Nitrogen Availability and Metabolism." Biomolecules 10, no. 12 (2020). Abstract

The use of actinomycetes for improving soil fertility and plant production is an attractive strategy for developing sustainable agricultural systems due to their effectiveness, eco-friendliness, and low production cost. Out of 17 species isolated from the soil rhizosphere of legume crops, 4 bioactive isolates were selected and their impact on 5 legumes: soybean, kidney bean, chickpea, lentil, and pea were evaluated. According to the morphological and molecular identification, these isolates belong to the genus Streptomyces. Here, we showed that these isolates increased soil nutrients and organic matter content and improved soil microbial populations. At the plant level, soil enrichment with actinomycetes increased photosynthetic reactions and eventually increased legume yield. Actinomycetes also increased nitrogen availability in soil and legume tissue and seeds, which induced the activity of key nitrogen metabolizing enzymes, e.g., glutamine synthetase, glutamate synthase, and nitrate reductase. In addition to increased nitrogen-containing amino acids levels, we also report high sugar, organic acids, and fatty acids as well as antioxidant phenolics, mineral, and vitamins levels in actinomycete treated legume seeds, which in turn improved their seed quality. Overall, this study shed the light on the impact of actinomycetes on enhancing the quality and productivity of legume crops by boosting the bioactive primary and secondary metabolites. Moreover, our findings emphasize the positive role of actinomycetes in improving the soil by enriching its microbial population. Therefore, our data reinforce the usage of actinomycetes as biofertilizers to provide sustainable food production and achieve biosafety.

Al-Wakeel, S. A. M., M. A. Gabr, and W. Abu El-Soud. "Allelopathic effects of Acacia nilotica leaf residue on Pisum sativum L." Allelopathy Journal 19, no. 2 (2007): 411-422. Abstract2007_al_wakeel_et_al.pdfWebsite

A greenhouse pot experiment was conducted to assess the allelopathic effects of Acacia nilotica leaves on the growth and metabolic activities of 45-day-old pea (Pisum sativum L.) plants. Qualitative and quantitative HPLC analysis of water extract of Acacia nilotica leaves revealed that protocatechuic and caffeic acids were the principal phenolic compounds accompanied by major amounts of ferulic, cinnamic acids and apigenin; whereas, pyrogallic, p-coumaric, syringic acids and coumarin were found in trace amounts. The lower doses of Acacia leaf residue (0.25 and 0.5%, w/w) stimulated the growth of pea shoot and root, but the higher doses (0.75, 1.0, 1.5 and 2%, w/w) were inhibitory to seedling growth and the effect was concentration dependent. The total phenolic content of pea shoots (particularly phenolic glycosides), increased at lower doses of Acacia residue and decreased with higher ones While, the phenolic aglycones increased with higher doses than lower ones. Chlorophyll a, b and carotenoids accumulated in pea shoot at lower doses of Acacia leaf residues, accompanied by accumulation of total sugar, mainly the insoluble fraction. On the other hand, the inhibition in the contents of photosynthetic pigments at higher doses of Acacia residues was paralleled by significant reduction in all sugar fractions. The contents of total nitrogen and phosphorus (their insoluble forms), increased with lower Acacia residues (0.25 and 0.5%); whereas all nitrogen and phosphorus fractions declined by increasing Acacia doses up to 1%. The total nucleic acids, including DNA and RNA increased with lower Acacia residue doses and gradually declined with the increase in Acacia level up to 1%.

Mohamed, Mervat S., Walid Abu El-Soud, and Magda F. Mohamed. "Cloning and expression of the recombinant NP24I protein from tomato fruit and study of its antimicrobial activity." AFRICAN JOURNAL OF BIOTECHNOLOGY 10 (2011): 14276-14285. Abstract

Thaumatin-like proteins (TLPs) constitutes a homogeneous family, members of which are produced by plants in response to different kinds of stress. NP24 protein is one of such salt-induced protein from tomato (Solanum lycopersicum) and it belongs to TLPs family. NP24 is a 24 kDa (207 amino acid) antimicrobial TLP found in tomato fruits. One isoform (NP24I) of NP24 was discovered in the outer pericarp of tomato fruit and is reported to play a possible role in ripening of the fruit in addition to its antimicrobial activity. In this study, the total RNA was isolated successfully from the outer pericarp of ripe (red) tomato fruit. cDNA was prepared and the gene coding for NP24I protein was amplified using conventional polymerase chain reaction (PCR). The gene was then cloned into Mach1 (TM)- T1 (R) Escherichia coli cells, then subcloned into the over-expression vector pET-28a (+) using BL21 expression bacteria. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the gene was over-expressed in E. coli as inclusion bodies. Optimization of the recombinant NP24I protein solubility was achieved by cold induction through decreasing both expression temperature and Isopropyl-beta-thio galactopyranoside (IPTG) concentration. The recombinant NP24I protein was purified using Ni-NTA resin, and then the antimicrobial activity of the purified recombinant NP24I protein was tested. The aims of this work were to study the cloning and expression of NP24 protein from local tomato cultivar in a prokaryotic system and to test the activity of the recombinant NP24, as well as to prove the activity of native protein on the bacterial as well as fungal growth.

Al-Wakeel, S. M., M. M. A. Gabr, W. M. Abu-El-Soud, and A. M. Saleh. "Coumarin and salicylic acid activate resistance to Macrophomina phaseolina in Helianthus annuus." Acta Agronomica Hungarica 61, no. 1 (2013): 23-35. Abstract2013_al-wakeel_et_al.pdf

The induction of resistance to charcoal rot disease caused by Macrophomina phaseolina (Tassi) Goidanich in sunflower (Helianthus annuus L.) was studied after seed treatments with coumarin (COU) and salicylic acid (SA) at three different levels (0.3, 1.0 and 3.0 mM). The priming of sunflower seeds with 0.3 mM COU or 1.0 mM SA resulted in decreased disease severity and offered about 50% protection and more than 80% reduction in the length of stem lesions under greenhouse conditions. Both COU and SA treatments induced the accumulation of soluble sugars and phytoalexins, as well as stimulating the activity of β-1,3-glucanase and chitinase.

Gourcilleau, D., M. B. Bogeat-Triboulot, D. Le Thiec, C. Lafon-Placette, A. Delaunay, W. Abu El-Soud, F. Brignolas, and S. Maury. "DNA methylation and histone acetylation: genotypic variations in hybrid poplars, impact of water deficit and relationships with productivity." ANNALS OF FOREST SCIENCE 67, no. 2 (2010): 208. AbstractWebsite

Several reports on annual plants have already shown the involvement of epigenetic modifiers such as DNA methylation in their adaptation to abiotic stresses.
Nevertheless, the genotypic variations of epigenetic modifiers, their possible correlations with morphological traits and the impact of water deficit have not been described for perennial plants.
Six genotypes of Populus deltoides x P. nigra were subjected or not to a moderate water deficit treatment. Various morphological traits such as the height of the plants, their biomass and the total leaf area were measured to characterize the productivity in both conditions. Levels of DNA methylation, histone acetylation and the activities and isoform accumulation of the corresponding enzymes were measured at the shoot apex, the site of morphogenesis. Genotypic variation was observed for the morphological traits and the epigenetic variables and correlations were established among them. Genotypic variation for DNA methylation was detected in hybrid poplars. A positive correlation was demonstrated between DNA methylation percentage and productivity under well watered conditions.
While there was a general decrease of growth for all genotypes in response to a moderate water deficit, genotypic dependant variations of DNA methylation were found suggesting different strategies among hybrids.

Abuelsoud, Walid, and Jutta Papenbrock. "Drought differentially elicits antioxidant defense systems in two genotypes of Euphorbia tirucalli." 259 (2019): 151460. AbstractWebsite

Euphorbia tirucalli, a member of Euphorbiaceae, is a drought and salt-tolerant species. It is distributed in subtropical and semi-arid parts of Africa and was brought to Asia and North America. The plant has succulent stems performing CAM metabolism and small non-succulent leaves performing C3 metabolism. Different genotypes of E. tirucalli showed different tolerance to drought stress, especially Morocco and Senegal genotypes. This difference has tempted us to investigate the difference in antioxidant stress mechanisms in stems as compared to leaves. Plants from both genotypes have been subjected to drought (10% Volumetric Water Content, VWC) for 8 weeks and the leaves and stems were investigated for their reactive oxygen species (ROS) and antioxidants levels. Shoots of Morocco genotype retained water more efficiently under drought compared to Senegal shoots. Although H2O2 accumulated in stems under drought compared to leaves, however, the stems have elevated levels of various non-enzymatic and enzymatic antioxidants. Stems of Morocco increased their levels of H2O2 more under drought compared to Senegal stems, and Morocco stems showed a higher increase in their non-enzymatic and enzymatic antioxidants under drought. Morocco stems are distinguished by increased ascorbate peroxidase (APX) and peroxidase (POX) activities, while in Senegal stems catalase (CAT) activity specifically increased under drought. Levels of H2O2 in leaves were higher as compared to stems even under control conditions; however, leaves did not show increased antioxidant enzymes levels under drought stress. This tendency to accumulate H2O2 could be used by E. tirucalli as strategy to kill and get rid of leaves under drought to reduce transpirational water loss. These differences in antioxidant systems of Morocco and Senegal genotypes could, at least partly, explain their differences in drought tolerance and may reflect evolutionary adaptations to different local native climates.

Selim, Samy, Walid Abuelsoud, Mohammad M. Al-Sanea, and Hamada AbdElgawad. "Elevated CO2 differently suppresses the arsenic oxide nanoparticles-induced stress in C3 (Hordeum vulgare) and C4 (Zea maize) plants via altered homeostasis in metabolites specifically proline and anthocyanin metabolism." 166 (2021): 235-245. AbstractWebsite

Nano-sized arsenic oxide nanoparticles (As2O3-NP) limit crop growth and productivity. As2O3-NP represent a strong environmental hazard. The predicted rise in future atmospheric CO2 could boost plant growth both under optimal and heavy metal stress conditions. So far, the phytotoxicity of As2O3-NP and their interaction with eCO2 were not investigated at physiological and metabolic levels in crop species groups such as C3 and C4. We investigated how eCO2 level (620 ppm) alleviated soil As2O3-NP toxicity induced growth and mitigated oxidative damages through analysing photosynthetic parameters, primary (sugars and amino acids) and secondary (phenolics, flavonoids and anthocyanins) metabolism in C3 (barley) and C4 (maize) plants. Compared to maize, barley accumulated higher As2O3-NP level, which inhibited growth and induced oxidative damage particularly in barley (increased H2O2 and lipid peroxidation). Interestingly, eCO2 differently mitigated As2O3-NP toxicity on photosynthesis, which consequently improved sugar metabolism. Moreover, high carbon availability in eCO2 treated plants directed to produce osmo-protectant (soluble sugars and proline) and antioxidants (anthocyanins and tocopherols). In the line with increased proline and anthocyanins, their metabolism was also improved. Notable differences occurred between the two plant species. The ornithine pathway was preferred in maize while in barley proline accumulation was mainly through glutamate pathway. Moreover, under As2O3-NP stress, barley preferentially accumulated anthocyanins while maize accumulated total phenolics and flavonoids. This work contributes to improving our understanding of the differences in growth, physiological and biochemical responses of major crops of two functional photosynthetic groups (C3 and C4 plants) under ambient and elevated CO2 grown under As2O3-NP stress.

Saleh, A. M., and W. Abu El-Soud. "Evidence for “gibberellin-like” activity of coumarin." 100 (2015): 51-57. AbstractWebsite

AbstractThe existing body of information defines some regulatory functions to secondary metabolites like coumarin (COU). Experience and some experimental results in our laboratory tempted us to test a GA-like activity of COU. Experiments were conducted with endospermic (de-embryonated) and embryonic wheat half grains treated with different concentrations of COU, for different time courses, alone or in combination with the GA-biosynthesis inhibitor paclobutrazol (P). Results showed that treatment with COU caused stimulation of amylase synthesis and secretion from aleurone layer cells. P did not affect synthesis but slightly reduced excretion of amylase. However, germination percentage of intact wheat grains and seedling growth were inhibited by COU in a concentration-dependent manner. This indicates that COU has some GA-like effect, and also affects other aspects of germination and seedling establishment. This GA-like effect was also confirmed by the observed increase in elongation of wheat seedlings second leaf sheath and pea stem when treated with COU. These potential regulatory roles of COU may indicate that secondary metabolites have more important roles during different plant developmental processes.

Hozzein, Wael N., Walid Abuelsoud, Mohammed A. M. Wadaan, Ahmed M. Shuikan, Samy Selim, Soad Al Jaouni, and Hamada AbdElgawad. "Exploring the potential of actinomycetes in improving soil fertility and grain quality of economically important cereals." The Science of the total environment 651, no. Pt 2 (2019): 2787-2798. Abstract

The search for environment-friendly, economical and healthy alternatives to agrochemicals tempted us to evaluate the potential of naturally occurring actinomycetes to improve soil properties, plant growth and photosynthesis, grain yield and chemical composition of economically important cereals (wheat, barley, oat, maize and sorghum). To this end, actinomycetes were isolated from soils of local cereals fields, then their biological activities, namely antibacterial, antiprotozoal, antioxidant, and phenolic and flavonoid contents were evaluated. The four most active isolates (9, 16, 24 and 26) were selected and used for enriching the soils until seed set. Each isolate was separately applied. Seeds of the selected cereals were grown in the actinomycete-enriched soils. The soils were analyzed for their electrical conductivity, pH values, total phenolics, organic matter and mineral content. At the vegetative stage, chlorophyll content and gas exchange rates were measured. Mature seeds were then harvested, the yield was evaluated and the seeds were analyzed for their primary and secondary metabolites. The selected isolates improved the grain yield in all tested cereals and most noticeably in barley and maize as compared to control counterparts. These positive effects were probably a result of increased carbon gain due to higher chlorophyll and photosynthetic rate. Isolate 26 showed the highest effect on grains composition profiles followed by the isolate 16. Phenolics and sugars of all grains increased by treatment with the tested isolates. Isolate 26 was the most effective in this regard. All isolates generally improved vitamins, amino acids and organic acids contents in grains. However, fatty acids profile showed a decrease in the content of all measured fatty acids by isolate 26 and an increase in the contents by isolate 16. These results emphasize the potential of actinomycete enrichment as an alternative to agrochemicals and strongly suggest that they can be used in organic farming.

AbdElgawad, Hamada, Gaurav Zinta, Momtaz Mohamed Hegab, Renu Pandey, Han Asard, and Walid Abuelsoud. "High salinity induces different oxidative stress and antioxidant responses in maize seedlings organs." Frontiers in Plant Science 7 Article 276 (2016). AbstractWebsite

Salinity negatively affects plant growth and causes significant crop yield losses world-wide. Maize is an economically important cereal crop affected by high salinity. In this study, maize seedlings were subjected to 75 mM and 150 mM NaCl, to emulate high soil salinity. Roots, mature leaves (basal leaf-pair 1,2) and young leaves (distal leaf-pair 3,4) were harvested after 3 weeks of sowing. Roots showed the highest reduction in biomass, followed by mature and young leaves in the salt-stressed plants. Concomitant with the pattern of growth reduction, roots accumulated the highest levels of Na+ followed by mature and young leaves. High salinity induced oxidative stress in the roots and mature leaves, but to a lesser extent in younger leaves. The younger leaves showed increased electrolyte leakage (EL), malondialdehyde (MDA), and hydrogen peroxide (H2O2) concentrations only at 150 mM NaCl. Total antioxidant capacity (TAC) and polyphenol content increased with the increase in salinity levels in roots and mature leaves, but showed no changes in the young leaves. Under salinity stress, reduced ascorbate (ASC) and glutathione (GSH) content increased in roots, while total tocopherol levels increased specifically in the shoot tissues. Similarly, redox changes estimated by the ratio of redox couples (ASC/total ascorbate and GSH/total glutathione) showed significant decreases in the roots. Activities of enzymatic antioxidants, catalase (CAT, EC 1.11.1.6) and dehydroascorbate reductase (DHAR, EC 1.8.5.1), increased in all organs of salt-treated plants, while superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione-s-transferase (GST, EC 2.5.1.18) and glutathione reductase (GR, EC 1.6.4.2) increased specifically in the roots. Overall, these results suggest that Na+ is retained and detoxified mainly in roots, and less stress impact is observed in mature and younger leaves. This study also indicates a possible role of ROS in the systemic signaling from roots to leaves, allowing leaves to activate their defense mechanisms for better protection against salt stress.

Madany, Mahmoud M. Y., Gaurav Zinta, Walid Abuelsoud, Wael N. Hozzein, Samy Selim, Han Asard, and Hamada AbdElgawad. "Hormonal seed-priming improves tomato resistance against broomrape infection." Journal of Plant Physiology 250 (2020): 153184. AbstractWebsite

Although it is well known that parasitic weeds such as Orobanche (broomrape) significantly reduce the yield of economically important crops, their infection-induced oxidative changes need more exploration in their host plants. Moreover, applying an eco-friendly approach to minimize the infection is not yet available. This study was conducted to understand the effect of Orobanche ramosa infection on oxidative and redox status of tomato plants and the impact of hormonal (indole acetic acid (IAA); 0.09 mM and salicylic acid (SA); 1.0 mM) seed-priming upon mitigating the infection threats. Although Orobanche invades tomato roots, its inhibitory effects on shoot biomass were also indicted. Orobanche infection usually induces oxidative damage i.e., high lipid peroxidation, lipoxygenase activity and H2O2 levels, particularly for roots. Interestingly, hormonal seed-priming significantly enhanced tomato shoots and roots growth under both healthy and infected conditions. Also, IAA and SA treatment significantly reduced Orobanche infection-induced oxidative damage. The protective effect of seed-priming was explained by increasing the antioxidant defense markers including the antioxidant metabolites (i.e., total antioxidant capacity, carotenoids, phenolics, flavonoids, ASC, GSH, tocopherols) and enzymes (CAT, POX, GPX, SOD, GR, APX, MDHAR, DHAR), particularly in infected tomato seedlings. Additionally, cluster analysis indicated the differential impact of IAA- and SA-seed-priming, whereas lower oxidative damage and higher antioxidant enzymes’ activities in tomato root were particularly reported for IAA treatment. The principal component analysis (PCA) also proclaimed an organ specificity depending on their response to Orobanche infection. Collectively, here and for the first time, we shed the light on the potential of seed-priming with either IAA or SA to mitigate the adverse effect of O. ramosa stress in tomato plants, especially at oxidative stress levels.

Selim, Samy, Walid Abuelsoud, Salam S. Alsharari, Bassam F. Alowaiesh, Mohammad M. Al-Sanea, Soad Al Jaouni, Mahmoud M. Y. Madany, and Hamada AbdElgawad. "Improved Mineral Acquisition, Sugars Metabolism and Redox Status after Mycorrhizal Inoculation Are the Basis for Tolerance to Vanadium Stress in C3 and C4 Grasses." Journal of Fungi 7 (2021). AbstractWebsite

Vanadium (V) can be beneficial or toxic to plant growth and the interaction between arbuscular mycorrhizal fungi (AMF) and V stress was rarely investigated at physiological and biochemical levels of plant groups (C3 and C4) and organs (roots and shoots). We tested the potential of AMF to alleviate the negative effects of V (350 mg V/Kg soil) on shoots and roots of rye and sorghum. Relative to sorghum (C4), rye (C3) showed higher levels of V and lower levels of key elements under V stress conditions. V inhibited growth, photosynthesis, and induced photorespiration (increased HDR & GO activities) and oxidative damage in both plants. AMF colonization reduced V stress by differently mitigating the oxidative stress in rye and sorghum. This mitigation was accompanied with increases in acid and alkaline phosphatase activities in plant roots and increased organic acids and polyphenols exudation into the soil, thus reduced V accumulation (29% and 58% in rye and sorghum shoot, respectively) and improved absorption of mineral nutrients including Ca, Mg and P. AMF colonization improved photosynthesis and increased the sugar accumulation and metabolism. Sugars also acted as a supplier of C skeletons for producing of antioxidants metabolite such as ascorbate. At the antioxidant level, rye was more responsive to the mitigating impact of AMF. Higher antioxidants and detoxification defence system (MTC, GST, phenolics, tocopherols and activities of CAT, SOD and POX) was recorded for rye, while sorghum (C4) improved its GR activity. The C3/C4-specificity was supported by principal component analysis. Together, this study provided both fundamental and applied insights into practical strategies to mitigate the phytotoxicity hazards of V in C3 and C4 grasses. Moreover, our results emphasize the importance of AMF as an environment-friendly factor to alleviate stress effects on plants and to improve growth and yield of unstressed plants.

AbdElgawad, Hamada, Gaurav Zinta, Badreldin A. Hamed, Samy Selim, Gerrit Beemster, Wael N. Hozzein, Mohammed A. M. Wadaan, Han Asard, and Walid Abuelsoud. "Maize roots and shoots show distinct profiles of oxidative stress and antioxidant defense under heavy metal toxicity." Environmental Pollution 258 (2020): 113705. AbstractWebsite

Heavy metal accumulation in agricultural land causes crop production losses worldwide. Metal homeostasis within cells is tightly regulated. However, homeostasis breakdown leads to accumulation of reactive oxygen species (ROS). Overall plant fitness under stressful environment is determined by coordination between roots and shoots. But little is known about organ specific responses to heavy metals, whether it depends on the metal category (redox or non-redox reactive) and if these responses are associated with heavy metal accumulation in each organ or there are driven by other signals. Maize seedlings were subjected to sub-lethal concentrations of four metals (Zn, Ni, Cd and Cu) individually, and were quantified for growth, ABA level, and redox alterations in roots, mature leaves (L1,2) and young leaves (L3,4) at 14 and 21 days after sowing (DAS). The treatments caused significant increase in endogenous metal levels in all organs but to different degrees, where roots showed the highest levels. Biomass was significantly reduced under heavy metal stress. Although old leaves accumulated less heavy metal content than root, the reduction in their biomass (FW) was more pronounced. Metal exposure triggered ABA accumulation and stomatal closure mainly in older leaves, which consequently reduced photosynthesis. Heavy metals induced oxidative stress in the maize organs, but to different degrees. Tocopherols, polyphenols and flavonoids increased specifically in the shoot under Zn, Ni and Cu, while under Cd treatment they played a minor role. Under Cu and Cd stress, superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR) activities were induced in the roots, however ascorbate peroxidase (APX) activity was only increased in the older leaves. Overall, it can be concluded that root and shoot organs specific responses to heavy metal toxicity are not only associated with heavy metal accumulation and they are specialized at the level of antioxidants to cope with.

Abuelsoud, Walid, Anne Cortleven, and Thomas Schmülling. "Photoperiod stress induces an oxidative burst-like response and is associated with increased apoplastic peroxidase and decreased catalase activities." Journal of Plant Physiology 253 (2020): 153252. AbstractWebsite

Periodic changes of light and dark regulate numerous processes in plants. Recently, a novel type of stress caused by an extended light period has been described in Arabidopsis thaliana and was named photoperiod stress. Although photoperiod stress causes the induction of numerous stress response genes of which many are indicators of oxidative stress, the exact timing and mechanisms involved in dealing with this stress have not yet been investigated. We describe the response of the cellular redox system in wild-type Arabidopsis and the photoperiod stress sensitive cytokinin receptor mutant ahk2 ahk3 and the clock mutant cca1 lhy. Photoperiod stress caused several changes in the ROS scavenging system including a reduction of the ascorbic acid (AsA) redox status and strong peroxide formation during the night following the extended photoperiod. The changes were associated with reduced catalase (CAT) and increased apoplastic peroxidase (PRX) activities. Consistently, the expression of the apoplastic PRX genes PRX4, PRX33, PRX34 and PRX71 was strongly induced by photoperiod stress. We show that extending the light period by only few hours may cause a stress response during the following night suggesting that the photoperiod stress response might occur in a natural setting.

Causevic, Adisa, Marie-Véronique Gentil, Alain Delaunay, Walid El-Soud, Zacarias Garcia, Christophe Pannetier, Franck Brignolas, Daniel Hagège, and Stéphane Maury. "Relationship between DNA methylation and histone acetylation levels, cell redox and cell differentiation states in sugarbeet lines." Planta 224 (2006): 812-827. AbstractWebsite
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AbdElgawad, Hamada, Sébastjen Schoenaers, Gaurav Zinta, Yasser M. Hassan, Mohamed Abdel-Mawgoud, DalalHussien M. Alkhalifah, Wael N. Hozzein, Han Asard, and Walid Abuelsoud. "Soil arsenic toxicity differentially impacts C3 (barley) and C4 (maize) crops under future climate atmospheric CO2." 414 (2021): 125331. AbstractWebsite

Soil arsenic (As) contamination limits global agricultural productivity. Anthropogenic emissions are causing atmospheric CO2 levels to rise. Elevated CO2 (eCO2) boosts plant growth both under optimal and suboptimal growth conditions. However, the crop-specific interaction between eCO2 and soil arsenic exposure has not been investigated at the whole plant, physiological and biochemical level. Here, we tested the effects of eCO2 (620 ppm) and soil As exposure (mild and severe treatments, 25 and 100 mg As/Kg soil) on growth, photosynthesis and redox homeostasis in barley (C3) and maize (C4). Compared to maize, barley was more susceptible to soil As exposure at ambient CO2 levels. Barley plants accumulated more As, particularly in roots. As accumulation inhibited plant growth and induced oxidative damage in a species-specific manner. As-exposed barley experienced severe oxidative stress as illustrated by high H2O2 and protein oxidation levels. Interestingly, eCO2 differentially mitigated As-induced stress in barley and maize. In barley, eCO2 exposure reduced photorespiration, H2O2 production, and lipid/protein oxidation. In maize eCO2 exposure led to an upregulation of the ascorbate-glutathione (ASC/GSH)-mediated antioxidative defense system. Combined, this work highlights how ambient and future eCO2 levels differentially affect the growth, physiology and biochemistry of barley and maize crops exposed to soil As pollution.

Selim, Samy, Hamada AbdElgawad, Salam S. Alsharari, Muhammad Atif, Mona Warrad, Nashwa Hagagy, Mahmoud M. Y. Madany, and Walid Abuelsoud. "Soil enrichment with actinomycete mitigates the toxicity of arsenic oxide nanoparticles on wheat and maize growth and metabolism." Physiologia PlantarumPhysiologia Plantarum 173, no. 3 (2021): 978-992. AbstractWebsite

Abstract The use of plant growth-promoting bacteria (PGPB) to enhance plant growth and protection against heavy metal toxicity has been extensively studied. However, its potentiality to reduce arsenate toxicity, a threat to plant growth and metabolism, has been hardly investigated. Moreover, the toxic effect of arsenic oxide nanoparticles (As-NPs) on plants and possible mechanisms for its alleviation has not yet been explored. In this study, the impact of the bioactive actinomycete Streptomyces spp. on the growth, physiology and stress-related metabolites, such as sugars and proline, on As-NPs-stressed wheat and maize plants was investigated. Soil amendment with arsenic oxide nanoparticles (As-NPs) induced the uptake and accumulation of As in the plants of both species, resulting in reduced growth and photosynthesis, but less marked in maize than in wheat plants. Under As-NPs-free conditions, Streptomyces spp. treatment markedly improved growth and photosynthesis in wheat only. The application of Streptomyces spp. reduced As accumulation, recovered the As-NPs-induced growth, photosynthesis inhibition, and oxidative damage in plants of both species. Wheat plants specifically accumulated soluble sugars, while both species accumulated proline. Under As-NPs stress, the ornithine pathway of proline biosynthesis was more important in maize than in wheat plants, while the glutamine pathway was dominant in wheat ones. The addition of Streptomyces spp. further induced the accumulation of proline and starch in both plant species. Overall, despite a different response to Streptomyces spp. under nontoxic conditions, the amendment of as-contaminated soil with Streptomyces spp. induced similar metabolic responses in the two tested species, which trigger stress recovery.

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