Plasma Membrane NADPH Oxidase Research Articles

Aquaporin-7 Facilitates Proliferation and Adipogenic Differentiation of Mouse Bone Marrow Mesenchymal Stem Cells by Regulating Hydrogen Peroxide Transport.

Hydrogen peroxide (H2O2) is a major form of reactive oxygen species that play an important role in the survival, proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs). The regulatory mechanisms of H2O2 homeostasis in BMSCs are not fully understood. Here we demonstrate for the first time that aquaglyceroporin AQP7 is a functional peroxiporin expressed in BMSCs and remarkably upregulated upon adipodenic induction. The proliferation ability of BMSCs from AQP7-/- mice was significantly decreased, as indicated by fewer clonal formation and cell cycle arrest compared with wildtype BMSCs. AQP7 deficiency caused accumulation of intracellular generated H2O2 during BMSCs proliferation, leading to oxidative stress and inhibition of PI3K/AKT and STAT3 signaling pathways. After adipogenic induction, however, the AQP7-/- BMSCs exhibited greatly reduced adipogenic differentiation with fewer lipid droplets formation and lower cellular triglycerides content than wildtype BMSCs. In such case AQP7 deficiency was found to diminish import of extracellular H2O2 produced by plasma membrane NADPH Oxidases, resulting in altered AMPK and MAPK signaling pathways and reduced expression of lipogenic genes C/EBPα and PPARγ. Our data revealed a novel regulatory mechanism of BMSCs function through AQP7-mediated H2O2 transport across plasma membrane. AQP7 is a peroxiporin mediating H2O2 transport across the plasma membrane of BMSCs. During proliferation, AQP7 deficiency results in accumulation of intracellular generated H2O2 due to reduced export, which inhibited STAT3 and PI3K/AKT/insulin receptor signaling pathways and cell proliferation. During adipogenic differentiation, however, AQP7 deficiency blocked the uptake of extracelluar H2O2 generated through plasma membrane NOX enzymes. The reduced intracellular H2O2 level causes decreased expression of lipogenic genes C/EBPα and PPARγ due to altered AMPK and MAPK signaling pathways, leading to impaired adipogenic differentiation.

Role of Plasma Membrane NADPH Oxidase in Response to Salt Stress in Cucumber Seedlings.

Plasma membrane NADPH oxidases (RBOHs, EC 1.6.3.1) are known as the main ROS generators involved in plant adaptation to stress conditions. In the present work, regulation of NADPH oxidase was analyzed in cucumber (Cucumis sativus L. var. Krak) seedlings exposed to salinity. RBOH activity and gene expression, as well as H2O2 content, were determined in the roots of plants treated with 50 or 100 mM NaCl for 1 h, and 50 mM NaCl for 1 or 6 days. It was found that enzyme activity increased in parallel with an enhancement in the H2O2 level in roots exposed to 100 mM NaCl for 1 h, and to 50 mM NaCl for 1 day. The expression of some CsRboh genes was induced by salt. Moreover, an increase in the activity of G6PDH, providing the substrate for the NADPH oxidase, was observed. In seedlings subjected to salinity for a longer time, antioxidant enzymes—including superoxide dismutase, catalase, and ascorbate peroxidase—were activated, participating in maintaining a steady-state H2O2 content in the root cells. In conclusion, NADPH oxidase and endogenous H2O2 up-regulation seem to be early events in cucumber response to salinity.

Upregulated expression of RESPIRATORY BURST OXIDASE HOMOLOG D underlies lesion-mimic phenotype in dark-treated Arabidopsis pheide a oxygenase mutant leaves.

Upregulated expression of RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) encoding a plasma membrane NADPH oxidase is responsible for the lesion-mimic phenotype in detached Arabidopsis leaves with mutation of PHEIDE a OXYGENASE during extended darkness. Chlorophyll degradation is an indispensable process in leaf senescence, either age-dependent or dark-induced. Besides higher chlorophyll retention, a lesion-mimic phenotype (abbreviated as LMP afterwards) was exhibited in Arabidopsis leaves with mutation of PHEIDE a OXYGENASE (PaO) involved in chlorophyll degradation during dark incubation, but the associated mechanism remains elusive. We found that dark-treated pao leaves showed higher membrane damage and H2O2 accumulation, while scavenging H2O2 by its chemical scavenger diminished LMP. RBOHD which encodes NADPH oxidase was strikingly up-regulated in pao leaves during dark treatment. Chemical inhibition of NADPH oxidase or mutation of RBOHD in pao leaves suppressed LMP. Thus, our study suggests that up-regulated RBOHD transcription is responsible for the formation of LMP in dark-treated pao leaves and there may be a retrograde signaling pathway mediating upregulation of RBOHD which remains to be elucidated.

Nanoceria potently reduce superoxide fluxes from mitochondrial electron transport chain and plasma membrane NADPH oxidase in human macrophages.

Cerium oxide nanoparticles, also known as nanoceria, possess antioxidative and anti-inflammatory activities in animal models of inflammatory disorders, such as sepsis. However, it remains unclear how nanoceria affect cellular superoxide fluxes in macrophages, a critical type of cells involved in inflammatory disorders. Using human ML-1 cell-derived macrophages, we showed that nanoceria at 1-100μg/ml potently reduced superoxide flux from the mitochondrial electron transport chain (METC) in a concentration-dependent manner. The inhibitory effects of nanoceria were also shown in succinate-driven mitochondria isolated from the macrophages. Furthermore, nanoceria markedly mitigated the total intracellular superoxide flux in the macrophages. These data suggest that nanoceria could readily cross the plasma membrane and enter the mitochondrial compartment, reducing intracellular superoxide fluxes in unstimulated macrophages. In macrophages undergoing respiratory burst, nanoceria also strongly reduced superoxide flux from the activated macrophage plasma membrane NADPH oxidase (NOX) in a concentration-dependent manner. Token together, the results of the present study demonstrate that nanoceria can effectively diminish superoxide fluxes from both METC and NOX in human macrophages, which may have important implications for nanoceria-mediated protection against inflammatory disease processes.

Modulation of Intracellular ROS and Senescence-Associated Phenotypes of Xenopus Oocytes and Eggs by Selective Antioxidants.

Aging of oocytes and eggs diminishes their reproductive and developmental potential. It has been demonstrated previously that reactive oxygen species (ROS) contribute to accelerated aging of various cells. In the present study, we measured intracellular levels of ROS and investigated effects of several selective antioxidants (AOXs) on the viability and functional activity of aging oocytes and eggs of the African clawed frog Xenopus laevis. The fluorescent cell-permeable dye DCFDA, which is widely employed for ROS detection in cultured mammalian cells, was used to monitor ROS levels in the fresh and bench-aged oocytes and eggs by an optimized protocol. It was found that intracellular ROS contents were increased in frog oocytes and eggs aged for 48 h. It was further demonstrated using selective cell-permeable AOXs targeting different ROS-generating mechanisms, that the major source of ROS in Xenopus oocytes and eggs is the plasma membrane NADPH oxidase, and that mitochondrial generation contributes to the intracellular ROS content to a lesser extent. Targeted inhibition of NADPH oxidase with a natural organic compound apocynin reduced ROS levels significantly in Xenopus oocytes and eggs, maintained their normal phenotype and supported their functional competence. To our knowledge this is the first report concerning beneficial effects of apocynin on the isolated gamete cells, such as oocytes and eggs.

The Barley (Hordeum vulgare ssp. vulgare) Respiratory Burst Oxidase Homolog (HvRBOH) Gene Family and Their Plausible Role on Malting Quality.

Controlled generation of reactive oxygen species (ROS) is pivotal for normal plant development and adaptation to changes in the external milieu. One of the major enzymatic sources of ROS in plants are the plasma-membrane localized NADPH oxidases, also called as Respiratory Burst Oxidase Homologs (RBOH). In addition to the six previously reported, seven new members of RBOH gene family were identified in barley using in silico analysis. Conservation of genomic structure and key residues important for catalytic activity and co-factor binding was observed in barley RBOH genes. Phylogenetic analysis of plant RBOHs revealed distinct clades for monocot and dicot RBOH proteins. Hence, we propose to use the rice nomenclature for naming barley RBOH genes. Temporal changes in ROS profiles were observed during barley malting and was accompanied by changes in protein carbonylation, lipid peroxidation, and antioxidant capacity. Among the nine differentially expressed HvRBOHs during various malting stages, HvRBOHA and HvRBOHC showed most significant sustained changes in expression. RNAi knockdown lines with reduced expression of HvRBOHA/C gene exhibited genetic compensation via inducible expression of other gene family members during malting. However, the physiological consequence of reduced expression of HvRBOHA/C manifested as a poor malting quality profile attributable to low alpha-amylase activity and high levels of beta-glucan. We propose that the HvRBOHs play a critical role in modulating the redox milieu during the early stages of malting, which in turn can significantly impact carbohydrate metabolism.

Transcriptional co-regulation of plasma membrane H+-ATPase and NADPH oxidase during root growth

During root growth, plasma membrane NADPH oxidase (NOX) and PM H+-ATPase function cooperatively to maintain the membrane electrical balance while mediating cell growth through wall relaxation. A threshold [Ca+2]cyt and H2O2 mediate the feed-forward loop between these two enzymes in Vigna radiata seedlings. The apoplastic superoxide (O2ˉ) being produced by NOX is subsequently dismutated to H2O2 either spontaneously or by the activity of apoplastic Cu/Zn superoxide dismutase (SOD) enzyme. Since SOD utilises apoplastic H+ (extruded from cytosol by PM H+-ATPase) and O2ˉ as substrates, its functioning is inevitably depending on PM H+-ATPase and NOX activities. Further conversion of H2O2 by class III peroxidase (Prx) to hydroxyl radical (OH) is instrumental for wall polysaccharide cleavage and cell wall relaxation. Thus, SOD and Prx activities appear to be co-ordinated with the upstream interplay between NOX and PM H+-ATPase in the regulatory network for root growth (Majumdar and Kar, 2019, J Plant Physiol 232: 248–256). In the present investigation, possible co-regulation among NOX and PM H+-ATPase, at gene expression level, has been studied during root growth of V. radiata seedlings using quantitative real-time PCR (qRT-PCR). It is evident that a transcriptional co-regulation exists between the two enzymes and inhibition of any one enzyme or removal of its product represses gene expression of the other. As observed for their activities, H2O2 and Ca+2 apparently regulate expression of both NOX and PM H+-ATPase genes and the probable mechanism is discussed.

OsRbohB-mediated ROS production plays a crucial role in drought stress tolerance of rice.

We found that a rice NADPH oxidase gene OsRbohB contributes drought tolerance and its functions are involved in the interaction of the OsRbohB-mediated ROS production and ABA signaling. The plasma membrane NADPH oxidases, also known as respiratory burst oxidase homologs, are the key producers of ROS under both normal and stress conditions in plants. However, their functions in rice development and stress tolerance are still under investigation. Here, we found that a rice NADPH oxidase gene OsRbohB, also named OsNOX1, is expressed in all tissues examined throughout the development stages with higher transcripts in leaves. The transcriptional expression of OsRbohB is also strongly stimulated by dehydration, salt and several phytohormonal treatments. Compared with wide-type and the OsRbohB-overexpressing transgenic plants, osrbohB, a Tos17 insertion knockout mutant of OsRbohB, shows lower ROS production, abscisic acid (ABA) content and transcripts of a series of stress-related genes. The osrbohB mutant also exhibits lower seed germination rate, organ size and thousand seed weight, but higher stomatal aperture and sensitivity to drought. Moreover, a number of genes involved in plant development, stress response, transcriptional regulation, and particularly ABA signaling are differentially expressed in osrbohB plants under both normal growth and drought conditions. All these results suggest the roles of OsRbohB in drought tolerance of rice, which probably performed through the interaction of the OsRbohB-mediated ROS production and ABA signaling.

Jasmonic acid and hydrogen sulfide modulate transcriptional and enzymatic changes of plasma membrane NADPH oxidases (NOXs) and decrease oxidative damage in Oryza sativa L. during thiocyanate exposure.

It is evident that the plasma membrane NADPH oxidases (NOXs) play an important role in the generation of superoxide radicals (O2-•) in plants during defense responses. This study was to clarify activation of NOXs in oxidative damage in Oryza sativa during SCN- exposure, particularly in the roles of jasmonic acid (JA) and hydrogen sulfide (H2S) on transcriptional and enzymatic changes of NOXs. Results indicated that enzymatic activity of NOXs in both roots and shoots was significantly enhanced during SCN- exposure, whereas the application of JA and H2S donor (NaHS) significantly repressed NOXs activity in SCN-treated rice seedlings. Similarly, ROS analysis showed that SCN- exposure elevated the content of O2-•, hydrogen peroxide (H2O2) and malondialdehyde (MDA) in rice tissues significantly, whereas decreases in O2-• and H2O2 were detected in roots and shoots of SCN-treated rice seedlings due to application of JA and NaHS. PCR analysis revealed different expression patterns of 7 plasma membrane-localized NOX genes in rice roots and shoots against SCN- exposure, suggesting that various isogenes of NOXs might regulate and determine activity of NOXs in rice organs. In conclusion, SCN- exposure was able to trigger activation of NOXs effectively, and led to oxidative damage and lipid peroxidation; the effects of JA and NaHS on inactivation of NOXs was evident and tissue specific, which in turn modulated ROS accumulation in rice plants.

Class I phosphoinositide 3-kinases control sustained NADPH oxidase activation in adherent neutrophils

Phagocytes, especially neutrophils, can produce reactive oxygen species (ROS), through the activation of the NADPH oxidase (NOX2). Although this enzyme is crucial for host-pathogen defense, ROS production by neutrophils can be harmful in several pathologies such as cardiovascular diseases or chronic pulmonary diseases. The ROS production by NOX2 involves the assembly of the cytosolic subunits (p67phox, p47phox, and p40phox) and Rac with the membrane subunits (gp91phox and p22phox). Many studies are devoted to the activation of NOX2. However, the mechanisms that cause NADPH oxidase deactivation and thus terminate ROS production are not well known. Here we investigated the ability of class I phosphoinositide 3-kinases (PI3Ks) to sustain NADPH oxidase activation. The NADPH oxidase activation was triggered by seeding neutrophil-like PLB-985 cells, or human neutrophils on immobilized fibrinogen. Adhesion of the neutrophils, mediated by β2 integrins, induced activation of the NADPH oxidase and translocation of the cytosolic subunits at the plasma membrane. Inhibition of class I PI3Ks, and especially PI3Kβ, terminated ROS production. This deactivation of NOX2 is due to the release of the cytosolic subunits, p67phox and p47phox from the plasma membrane. Overexpression of an active form of Rac 1 did not prevent the drop of ROS production upon inhibition of class I PI3Ks. Moreover, the phosphorylation of p47phox at S328, a potential target of kinases activated by the PI3K pathway, was unchanged. Our results indicate that the experimental downregulation of class I PI3K products triggers the plasma membrane NADPH oxidase deactivation. Release of p47phox from the plasma membrane may involve its PX domains that bind PI3K products.

The fungal endophyte Epichloë gansuensis increases NaCl-tolerance in Achnatherum inebrians through enhancing the activity of plasma membrane H+-ATPase and glucose-6-phosphate dehydrogenase

Salt stress negatively affects plant growth, and the fungal endophyte Epichloëgansuensis increases the tolerance of its host grass species, Achnatherum inebrians, to abiotic stresses. In this work, we first evaluated the effects of E. gansuensis on glucose-6-phosphate dehydrogenase (G6PDH) and plasma membrane (PM) H+-ATPase activity of Achnatherum inebrians plants under varying NaCl concentrations. Our results showed that the presence of E. gansuensis increased G6PDH, PM H+-ATPase, superoxide dismutase and catalase activity to decrease O2•-, H2O2 and Na+ contents in A. inebrians under NaCl stress, resulting in enhanced salt tolerance. In addition, the PM NADPH oxidase activity and NADPH/NADP+ ratios were all lower in A. inebrians with E. ganusensis plants than A. inebrians plants without this endophyte under NaCl stress. In conclusion, E. gansuensis has a positive role in improving host grass yield under NaCl stress by enhancing the activity of G6PDH and PM H+-ATPase to decrease ROS content. This provides a new way for the selection of stress-resistant and high-quality forage varieties by the use of systemic fungal endophytes.

Genome-wide identification and expression analysis of NADPH oxidase genes in response to ABA and abiotic stresses, and in fibre formation in Gossypium.

Plasma membrane NADPH oxidases, also named respiratory burst oxidase homologues (Rbohs), play pivotal roles in many aspects of growth and development, as well as in responses to hormone signalings and various biotic and abiotic stresses. Although Rbohs family members have been identified in several plants, little is known about Rbohs in Gossypium. In this report, we characterized 13, 13, 26 and 19 Rbohs in G. arboretum, G. raimondii, G. hirsutum and G. barbadense, respectively. These Rbohs were conservative in physical properties, structures of genes and motifs. The expansion and evolution of the Rbohs dominantly depended on segmental duplication, and were under the purifying selection. Transcription analyses showed that GhRbohs were expressed in various tissues, and most GhRbohs were highly expressed in flowers. Moreover, different GhRbohs had very diverse expression patterns in response to ABA, high salinity, osmotic stress and heat stress. Some GhRbohs were preferentially and specifically expressed during ovule growth and fiber formation. These results suggest that GhRbohs may serve highly differential roles in mediating ABA signaling, in acclimation to environmental stimuli, and in fiber growth and development. Our findings are valuable for further elucidating the functions and regulation mechanisms of the Rbohs in adaptation to diverse stresses, and in growth and development in Gossypium.

Correction to: Heart Disease and Stroke Statistics-2019 Update: A Report From the American Heart Association.

Correction to: Heart Disease and Stroke Statistics-2019 Update: A Report From the American Heart Association.

Involvement of putrescine in osmotic stress-induced ABA signaling in leaves of wheat seedlings

To elucidate one mechanism by which putrescine (Put) functions in plant signaling under osmotic stress, Put and ABA contents, and plasma membrane-NADPH oxidase (PM-NOX) activity were detected in wheat seedling leaves. Under osmotic stress, ABA and Put contents, PM-NOX activity, and PM-NOX-dependent O2.- production all increased. The inhibitor tungstate (T) of ABA bio-synthesis reduced the increases in ABA and Put contents under osmotic stress. The inhibitor D-arginine (D-Arg) of Put bio-synthesis didn't reduce osmotic-induced increase of ABA, but it inhibited the increases of PM-NOX activity and O2 . - production, and the inhibitory effects were reversed by exogenous Put. These findings suggested that ABA might regulate Put biosynthesis, and Put might regulate PM-NOX activity. Treatments with three inhibitors imidazole (I), diphenylene iodonium (DPI) and pyridine (P) of PM-NOX reduced significantly not only O2 . - production, but also the stress-induced increase of Put content, which indicated that O2 . - production might regulate Put biosynthesis. Treatments with EGTA (Ca2+ chelator), La3+ and verapamil (V) (Ca2+ channel blockers) reduced significantly the stress-induced increase of Put content, which suggested that Ca2+ might regulate Put biosynthesis. With these findings, it could be concluded that Put was involved in ABA signaling induced by osmotic stress via regulating PM-NOX activity in wheat seedling leaves.

Generation of Superoxide by OeRbohH, a NADPH Oxidase Activity During Olive (Olea europaea L.) Pollen Development and Germination.

Reactive oxygen species (ROS) are produced in the olive reproductive organs as the result of intense metabolism. ROS production and pattern of distribution depend on the developmental stage, supposedly playing a broad panel of functions, which include defense and signaling between pollen and pistil. Among ROS-producing mechanisms, plasma membrane NADPH-oxidase activity is being highlighted in plant tissues, and two enzymes of this type have been characterized in Arabidopsis thaliana pollen (RbohH and RbohJ), playing important roles in pollen physiology. Besides, pollen from different species has shown distinct ROS production mechanism and patterns of distribution. In the olive reproductive tissues, a significant production of superoxide has been described. However, the enzymes responsible for such generation are unknown. Here, we have identified an Rboh-type gene (OeRbohH), mainly expressed in olive pollen. OeRbohH possesses a high degree of identity with RbohH and RbohJ from Arabidopsis, sharing most structural features and motifs. Immunohistochemistry experiments allowed us to localize OeRbohH throughout pollen ontogeny as well as during pollen tube elongation. Furthermore, the balanced activity of tip-localized OeRbohH during pollen tube growth has been shown to be important for normal pollen physiology. This was evidenced by the fact that overexpression caused abnormal phenotypes, whereas incubation with specific NADPH oxidase inhibitor or gene knockdown lead to impaired ROS production and subsequent inhibition of pollen germination and pollen tube growth.

Early Extracellular ATP Signaling in Arabidopsis Root Epidermis: A Multi-Conductance Process.

Adenosine 5′-triphosphate (ATP) is an important extracellular signaling agent, operating in growth regulation, stomatal conductance, and wound response. With the first receptor for extracellular ATP now identified in plants (P2K1/DORN1) and a plasma membrane NADPH oxidase revealed as its target, the search continues for the components of the signaling cascades they command. The Arabidopsis root elongation zone epidermal plasma membrane has recently been shown to contain cation transport pathways (channel conductances) that operate downstream of P2K1 and could contribute to extracellular ATP (eATP) signaling. Here, patch clamp electrophysiology has been used to delineate two further conductances from the root elongation zone epidermal plasma membrane that respond to eATP, including one that would permit chloride transport. This perspective addresses how these conductances compare to those previously characterized in roots and how they might operate together to enable early events in eATP signaling, including elevation of cytosolic-free calcium as a second messenger. The role of the reactive oxygen species (ROS) that could arise from eATP’s activation of NADPH oxidases is considered in a qualitative model that also considers the regulation of plasma membrane potential by the concerted action of the various cation and anion conductances. The molecular identities of the channel conductances in eATP signaling remain enigmatic but may yet be found in the multigene families of glutamate receptor-like channels, cyclic nucleotide-gated channels, annexins, and aluminum-activated malate transporters.

Increased bound putrescine accumulation contributes to the maintenance of antioxidant enzymes and higher aluminum tolerance in wheat

The accumulation of bound and conjugated polyamines (PAs) is an important protective trait in plants under adverse environmental conditions. However, their role in plant responses to aluminum (Al) stress remains largely unknown. In this study, we showed that Al treatment increased bound putrescine (Put) levels in the wheat root tips of Al-tolerant Xi Aimai-1, with little effect on its bound spermidine and conjugated PAs or that of Al-sensitive Yangmai-5. Terminating bound Put increments with a synthesis inhibitor (Phenanthroline, o-phen) exacerbated Al-induced root inhibition and callose production. However, it had no significant effect on Al uptake or distribution under Al stress. Instead, Al-induced reactive oxygen species (ROS) production and thus, oxidative damage, was greatly exacerbated by o-phen in the roots of Xi Aimai-1. Application of o-phen barely affected the two ROS generating enzymes (plasma membrane NADPH oxidase and cell wall-bound polyamine oxidase) in wheat roots. However, exogenous o-phen significantly reduced antioxidant enzyme (superoxide dismutase, ascorbate peroxidase, and catalase) activity, which positively correlated with the level of bound Put in Xi Aimai-1. These results clearly suggest that bound Put accumulation works to protect against Al-induced oxidative damage, possibly by maintaining antioxidant capacity in wheat.

Hydrogen peroxide metabolism and functions in plants.

Contents Summary 1197 I. Introduction 1198 II. Measurement and imaging of H2 O2 1198 III. H2 O2 and O2·- toxicity 1199 IV. Production of H2 O2 : enzymes and subcellular locations 1200 V. H2 O2 transport 1205 VI. Control of H2 O2 concentration: how and where? 1205 VII. Metabolic functions of H2 O2 1207 VIII. H2 O2 signalling 1207 IX. Where next? 1209 Acknowledgements 1209 References 1209 SUMMARY: Hydrogen peroxide (H2 O2 ) is produced, via superoxide and superoxide dismutase, by electron transport in chloroplasts and mitochondria, plasma membrane NADPH oxidases, peroxisomal oxidases, type III peroxidases and other apoplastic oxidases. Intracellular transport is facilitated by aquaporins and H2 O2 is removed by catalase, peroxiredoxin, glutathione peroxidase-like enzymes and ascorbate peroxidase, all of which have cell compartment-specific isoforms. Apoplastic H2 O2 influences cell expansion, development and defence by its involvement in type III peroxidase-mediated polymer cross-linking, lignification and, possibly, cell expansion via H2 O2 -derived hydroxyl radicals. Excess H2 O2 triggers chloroplast and peroxisome autophagy and programmed cell death. The role of H2 O2 in signalling, for example during acclimation to stress and pathogen defence, has received much attention, but the signal transduction mechanisms are poorly defined. H2 O2 oxidizes specific cysteine residues of target proteins to the sulfenic acid form and, similar to other organisms, this modification could initiate thiol-based redox relays and modify target enzymes, receptor kinases and transcription factors. Quantification of the sources and sinks of H2 O2 is being improved by the spatial and temporal resolution of genetically encoded H2 O2 sensors, such as HyPer and roGFP2-Orp1. These H2 O2 sensors, combined with the detection of specific proteins modified by H2 O2 , will allow a deeper understanding of its signalling roles.

Polyamines modulate aluminum-induced oxidative stress differently by inducing or reducing H2O2 production in wheat

Polyamines are important bioactive molecules involved in regulating H2O2 homeostasis, which is recognized as a major stimulus of oxidative stress under aluminum (Al) exposure. In this study, we investigated the involvement of spermidine oxidation in Al-induced oxidative stress, and its modulation by exogenous putrescine (Put) in two wheat genotypes differing in Al tolerance. Aluminum caused more severe oxidative damage at the root apexes in the Al-sensitive genotype Yangmai-5 than in the tolerant Xi Aimai-1, but these effects were significantly reversed by exogenous Put and polyamine oxidase (PAO) inhibitors. Aluminum caused a more significant increase in cell wall-bound PAO (CW-PAO) activity in Yangmai-5 than in Xi Aimai-1. Inhibiting of CW-PAO reduced H2O2 accumulation, restored Spd decline in both genotypes, indicating its potential role in Al-induced H2O2 production through catalyzing Spd oxidation. Additionally, Al significantly increased the activity of plasma membrane-NADPH oxidase, another H2O2 generator, in wheat roots. Put application significantly inhibited the activity of CW-PAO and plasma membrane-NADPH oxidase, and reduced H2O2 accumulation in Al-stressed wheat roots. Antioxidant enzymes were significantly stimulated by Al, but not Put. Overall, Put may protect wheat roots against Al-induced oxidative stress through regulating H2O2 production by inhibiting CW-PAO and plasma membrane-NADPH oxidase.

Glucose-6-phosphate dehydrogenase plays a vital role in Achnatherum inebrians plants host to Epichloë gansuensis by improving growth under nitrogen deficiency

Low nitrogen negatively affects soil fertility and plant productivity. Glucose-6-phosphate dehydrogenase (G6PDH) and Epichloe gansuensis endophytes are two factors that are associated with tolerance of Achnatherum inebrians to abiotic stress. However, the possibility that E. gansuensis interacts with G6PDH in enhancing low nitrogen tolerance of host grasses has not been examined. A. inebrians plants with (E+) and without E. gansuensis (E−) were subjected to different nitrogen concentration treatments (0.1, 1, and 7.5 mM). After 90 days, physiological studies were carried out to investigate the participation of G6PDH in the adaption of host plants to low nitrogen availability. Low nitrogen retarded the growth of A. inebrians. E+ plants had higher total dry weight, chlorophyll a and b contents, net photosynthesis rate, G6PDH activity, and GSH content, while having lower plasma membrane (PM) NADPH oxidase activity, NADPH/NADP+ ratios, and MDA and H2O2 than in E− A. inebrians plants under low nitrogen concentration. The presence of E. gansuensis played a key role in maintaining the growth of the A. inebrians plants under low nitrogen concentration by regulating G6PDH activity and the NADPH/NADP+ ratio and improving net photosynthesis rate.