Superoxide Content Research Articles

Physiological changes associated with enhanced cold resistance during Medicago ruthenica germination and seedling growth in response to exogenous γ‐aminobutyric acid

AbstractElucidating the effect of γ‐aminobutyric acid (GABA) on seed germination and seedling growth of Medicago ruthenica under low‐temperature could provide a reference for alleviating the harmful effects of low temperatures on legumes in alpine meadows. We set up different temperatures to screen three low temperatures that inhibit seed germination of Medicago ruthenica, and six aqueous concentrations of GABA (0, 0.1, 0.5, 1, 5, 10 mM) were set up to screen out the best GABA seed soaking concentration that can promote the seed germination at low‐temperature. The three temperatures of 10 °C, 20/5 °C and 15/5 °C inhibited seed germination of Medicago ruthenica. Soaking seeds with 1 mM GABA could significantly increase seed germination rate of Medicago ruthenica at low‐temperature (10 °C). Soaking seeds only with 0.1 mM GABA could promote germination of Medicago ruthenica at 20/5 °C, but there is no significant difference compared with distilled water soaking. Whereas, all GABA seed soaking concentrations delayed seed germination time and inhibited seed germination at 15/5 °C. Pre‐spraying seedlings with 1 mM GABA at 10 °C reduced the production of superoxide anion, hydrogen peroxide and malondialdehyde content, and increased the activities of catalase, peroxidase, superoxide dismutase and ascorbate peroxidase in leaves of Medicago ruthenica on days 7. Simultaneously, Pre‐spraying seedlings with 1 mM GABA at 10 °C significantly increased the net photosynthetic rate and decreased intercellular CO2 concentration. These data suggest that GABA could enhance the cold tolerance of Medicago ruthenica by promoting seed germination, regulating the antioxidant system, and increasing photosynthetic efficiency. However, the mitigation effect of GABA on low‐temperature is only applicable to a certain temperature. The mitigation effect of GABA on low temperature will be weakened as the low temperature of plants is less than 10 °C

5-Aminolevulinic Acid Ameliorates Salinity-Mediated Growth, Pysiological and Biochemical Changes In Mustard (Brassica Juncea L.)

5-aminolevulinic acid (ALA) is an important plant growth regulator which is derived from 5-carbon aliphatic amino acid. Here, ALA was examined in 12 dSm-1 salinity in growth and biochemical changes in mustard (Brassica juncea L. cv. BARI Sarisha-16) seedlings. Three NaCl mediated salinity levels (0, 8 and 12 dS m-1) were used with two ALA concentrations (30 and 60 mgL-1). Saline stress decreased plant height, root length, leaf area, dry mass accumulation, chlorophyll content, photosynthetic parameters, and K+, while proline (Pro), Na+, Na+/K+ ratio, antioxidant enzymatic activities, hydrogen peroxide (H2O2), superoxide (O2 •-), and melondialdehyde (MDA) content increased. Saline stressed mustard seedlings treated with 30 mgL-1 and 60 mgL-1 foliar application of ALA ameliorated the saline mediated inhibition in seedling growth i.e. increased plant height, root length, leaf area, and dry matter. ALA had also increase chlorophyll (Chl) content, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr), proline content as well as the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). In contrary, ALA decreased saline induced H2O2, O2 •-, and MDA while Na+ and Na+/K+ ratio increased. On the basis of the results, it was observed that ALA is a promising plant growth regulator which can improve plant survival under salinity.
 Bangladesh J. Agril. Res. 45(3): 217-231, September 2020

Persistent CD38 Expression on CD8 + T Lymphocytes Contributes to Altered Mitochondrial Function and Chronic Inflammation in People With HIV, Despite ART.

Age-associated comorbidities are higher in people with HIV (PWH) than HIV-negative individuals. This is partially attributed to immune activation and CD38 expression on T cells driving chronic inflammation. However, the exact contribution of CD38-expressing T cells on the proinflammatory response is not completely understood. CD38-expressing CD8 + T lymphocytes were measured from PWH and HIV-negative individuals. Mitochondrial mass, superoxide content, membrane depolarization of CD4 + and CD8 + T lymphocytes, and cytokine production after HIV(Gag)-specific peptide stimulation from CD38 + CD8 + T lymphocytes of PWH were measured to link biological effects of CD38 expression on cellular metabolism. The frequency of activated CD8 + CD38 + T cells persists in PWH on ART compared with HIV-negative individuals. Higher CD38 expression is associated with mitochondrial biogenesis and HIV(Gag)-specific proinflammatory cytokine production in PWH. Blockade of CD38 results in lower Gag-specific cytokine production. ART only partially reduced HIV-induced CD38 expression on CD8 + T cells. CD8 + CD38 + T cells are highly activated in vivo, and HIV-specific stimulation in vitro augments CD38 expression, contributing to a proinflammatory response despite virologic control with ART. Therefore, CD38 is a potential therapeutic target for mitigating chronic inflammation that likely drives cellular aging, comorbidities, and end-organ disease in PWH.

Exogenous melatonin improves salt tolerance mainly by regulating the antioxidant system in cyanobacterium Nostoc flagelliforme.

Melatonin is a multifunctional nontoxic bio-stimulant or signaling molecule, generally distributing in different animal and plant organs for invigorating numerous physiological processes against abiotic stresses. In this study, we investigated the potential impact of melatonin on the cyanobacterium Nostoc flagelliforme when exposed to salt stress according to some biochemical and physiological parameters, such as relative electrolyte leakage, PSII activity, and photosynthetic pigments including chlorophyll a, phycocyanobilin, and phycoerythrobilin. We found that melatonin could also maintain K+ homeostasis in salt-stressed N. flagelliforme. These above results confirmed melatonin had multiple functions in hyperosmotic stress and ion stress caused by salinity. Notably, we observed melatonin could regulate the reactive oxygen species (ROS) signal and distinctly decrease the content of hydrogen peroxide and superoxide anion in salt-stressed cells, which were largely attributed to the increased antioxidant enzymes activities including catalase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase. Finally, qRT-PCR analysis showed that melatonin stimulated the expression of antioxidant genes (NfCAT, NfSOD, and NfGR). In general, our findings demonstrate melatonin has beneficial effects on N. flagelliforme under salt stress by intensively regulating antioxidant system.

UV-C delays senescence in ‘Lingwu long’ jujube fruit by regulating ROS and phenylpropanoid metabolism

Ultraviolet (UV–C), a no residual environmentally friendly physical treatment, plays an important role in delaying the senescence in fruit. In this study, ‘Lingwu long’ jujubes were treated with UV-C (5 kJ m−2) to investigate the impacts of cell wall degrading enzymes (CWDEs) activities, reactive oxygen species (ROS) metabolism, and phenylpropanoid metabolism under storage at 4 ± 1 °C for 30 d. UV-C treatment reduced respiration rate and decay index. Treated fruit exhibited lower polygalacturonase (PG), pectinate lyases (PL), cellulase (Cel), and β-galactosidase (β-gal) activities which ultimately delayed the reduction of firmness. UV-C treatment increased hydrogen peroxide (H2O2), free radical scavenging ability, and superoxide dismutase (SOD) and catalase (CAT) activities, reduced superoxide anion (O2−) and malondialdehyde (MDA) content. In addition, ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) activities were activated by UV-C treatment, leading to glutathione (GSH) and ascorbic acid (AsA) increased. Besides, phenolic compounds of jujube fruit treated with UV-C were also increased, which might be due to the enhanced phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL) activities. In conclusion, UV-C was recommended for improving overall quality and alleviating senescence in jujube fruit.

Bio-Fermented Malic Acid Facilitates the Production of High-Quality Chicken via Enhancing Muscle Antioxidant Capacity of Broilers.

Malic acid, an intermediate of the tricarboxylic acid (TCA) cycle, is a promising acidifier with strong antioxidant capacity. This study aimed to evaluate the effects of bio-fermented malic acid (BFMA) on promoting the body health, performance and meat quality of broilers. A total of 288 one-day-old Arbor Acres male broiler chicks were randomly divided into four treatments with six replicates in each. Every replicate had 12 chicks. Four experimental diets contained 0, 4, 8, and 12 g/kg BFMA, respectively. During the 42-day trial, mortality was recorded daily, feed intake and body weight of each replicate being recorded every week. Blood samples were collected on days 21 and 42 for chemical analysis. After slaughter at the age of 42 days, the carcass traits and meat quality of the broilers were measured, breast muscle samples were collected for the determination of antioxidant capacity, and cecal digesta were pretreated for microbiota analysis. Dietary BFMA significantly increased feed intake and daily gain, and decreased feed conversion ratio and death and culling ratio of the broilers at the earlier stage. The water-holding capacity of breast muscle indicated by the indexes of dripping loss and cooking loss was significantly increased by BFMA, especially at the addition level of 8 g/kg. Dietary BFMA significantly decreased the activity of superoxide dismutase and contents of immunoglobulin A and glutathione, and increased contents of immunoglobulin G and M in serum of the broilers. The contents of glutathione, inosinic acid, and total antioxidant capacity and the activities of glutathione-Px and superoxide dismutase were significantly increased by dietary BFMA, with the level of 8 g/kg best. The diversity of cecal microbiota of broilers was obviously altered by BFMA. In conclusion, as one of several acidifiers, addition of BFMA in diets could improve the performance and body health of broilers, probably by reinforcing immunity and perfecting cecal microbiota structure. As one of the intermediates of the TCA cycle, BFMA increases the water-holding capacity of breast muscle of broilers, probably through reducing lactate accumulates and enhancing antioxidant capacity.

Endophytic Beauveria bassiana Induces Oxidative Stress and Enhances the Growth of Fusarium oxysporum-Infected Tomato Plants.

Studying the mechanisms through which endophytic fungi confer protection to host plants against parasites will contribute toward elucidating the endophytic fungi-plant-pathogen relationship. In this study, we evaluated the effects of endophytic Beauveria bassiana on the antioxidant activity, oxidative stress, and growth of tomatoes infected with the fusarium wilt pathogen, Fusarium oxysporum f. sp. lycopersici (FOL). Tomato seedlings were inoculated with B. bassiana conidia and then contaminated with FOL experimentally. Four treatments (Control [T1], FOL only [T2], B. bassiana only [T3], and B. bassiana and FOL [T4]) were assessed. The plants from the B. bassiana and FOL treatment (T4) were significantly taller (DF = 3, 56; p < 0.001) and produced more leaves and aerial part biomass than those treated with only FOL (T2). Remarkably, plants in the two treatments with FOL (T2 and T4) had the lowest antioxidant activities; meanwhile, plants from the FOL treatment (T2) had the lowest ROS (superoxide and hydroxyl radicals) contents. Broadly, strong positive correlations between ROS and all the plant growth parameters were recorded in this study. While the current results revealed that the endophytic entomopathogen B. bassiana enhanced antioxidant capacity in plants, it did not improve the antioxidant capacity of F. oxysporum-infected plants. It is possible that the pathogenic FOL employed a hiding strategy to evade the host immune response and the antagonistic actions of endophytic B. bassiana. In conclusion, B. bassiana inoculum enhanced the growth of tomatoes infected with FOL, induced higher oxidative stress in both F. oxysporum-infected and -uninfected tomatoes, and improved antioxidant activities in plants inoculated with B. bassiana only.

Brachypodium BdCHS is a homolog of Arabidopsis AtCHS involved in the synthesis of flavonoids and lateral root development.

Flavonoids are a kind of plant-specific secondary metabolites, which play an important role in regulating plant growth and development, stress response, and also have medicinal value. Chalcone synthase is the key enzyme in the synthesis of flavonoids. The function of chalcone synthase in Arabidopsis thaliana has been well studied, but its homologous protein in Brachypodium distachyon has not been reported. In this study, we identified a homolog of AtCHS in B. distachyon, named BdCHS, and described its function. Phylogenetic tree analysis showed that BdCHS was most closely related to CHS in Triticum aestivum. Transgene analysis revealed that BdCHS protein was localized in the cytoplasm of Arabidopsis root cells. BdCHS protein can complement the phenotype of AtCHS mutants with lighter seed coat color and increased lateral root density. The content of superoxide anion in the cortical cells above the lateral root primordium in AtCHS mutants was higher than that in the wild-type, and BdCHS protein could restore the content of superoxide anion in AtCHS mutant to the level of that in the wild-type. The results showed that BdCHS was a functional homolog of AtCHS, which laid a foundation for the subsequent application of BdCHS in genetic breeding and crop improvement.

Abscisic Acid, Paclobutrazol, and Salicylic Acid Alleviate Salt Stress in Populus talassica × Populus euphratica by Modulating Plant Root Architecture, Photosynthesis, and the Antioxidant Defense System

The exogenous plant growth regulators (PGRs) represent a useful strategy for reducing the adverse effects of salt stress in plants. In order to investigate the regulatory effect of exogenous PGRs on the salt tolerance of Populus talassica × Populus euphratica seedlings, in this study, the effects of different foliar spray concentrations of ABA (5 mg·L−1, 15 mg·L−1, 25 mg·L−1), PP333 (300 mg·L−1, 900 mg·L−1, 1500 mg·L−1), and SA (40 mg·L−1, 120 mg·L−1, 200 mg·L−1) on P. talassica × P. euphratica seedlings under salt stress (soil salt concentration of 2%) were determined. The results showed that the dry weight, total root length, root surface area, root volume, total Chl content, and photosynthetic parameters of P. talassica × P. euphratica seedlings significantly decreased under salt stress and increased their contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide anion (O2−), free proline (Pro), superoxide dismutase (SOD), and peroxidase (POD). However, ABA, PP333, and SA can mitigate the adverse effects of salt stress on these indicators. Especially, the 15 mg·L−1 ABA, 900 mg·L−1 PP333, and 120 mg·L−1 SA treatments had the best effect on alleviating salt stress, with significant increases in dry weight, root parameters, total Chl content, and the photosynthetic parameters of the P. talassica × P. euphratica seedlings, improving their photosynthetic characteristics; meanwhile, increased Pro content and enzyme activity and decreased MDA, H2O2, and O2− content protected the integrity of membrane system and enhanced the salt tolerance of the seedlings. SA resulted in a better ameliorative effect on salt stress compared to ABA and PP333.

Ecological roles of secondary metabolites of Saposhnikovia divaricata in adaptation to drought stress.

Saposhnikovia divaricata is a traditional Chinese herb that mainly grows in arid grasslands and strongly adapts to various stresses. Drought is not only a major abiotic stress factor but also a typical feature conducive to producing high-quality medicinal material. The present study investigated by treating S. divaricata plants with polyethylene glycol (PEG-6000). Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) identified 146 compounds from the roots of S. divaricata, among which seven primary metabolites and 28 secondary metabolites showed significant changes after drought treatment. UV-Vis spectrophotometer detected the activity of antioxidant enzymes and the content of superoxide anion (O2 -.) and malondialdehyde (MDA). The differential primary metabolites revealed that drought promotes glycolysis, reducing primary metabolism and enhancing secondary metabolism. Meanwhile, the differential secondary metabolites showed an increase in the content of compounds upstream of the secondary metabolic pathway, and other glycosides and increased that of the corresponding aglycones. The activities of antioxidant enzymes and the content of O2 -. and MDA shown different changes duing the drought treatment. These observations indicate that drought promotes the biosynthesis and transformation of the secondary metabolites and activity of antioxidant enzymes, improving plant adaptability. The present study also analyzed a few primary and secondary metabolites of S. divaricata under different degrees and durations of drought and speculated on the metabolic pathways in an arid environment. The findings indicate the biological nature, diversity, and complexity of secondary metabolites and the mechanisms of plant adaptation to ecological stress.

Sprayed biodegradable liquid film improved the freezing tolerance of cv. Cabernet Sauvignon by up-regulating soluble protein and carbohydrate levels and alleviating oxidative damage.

Most cultivars of Vitis vinifera L. are very sensitive to cold. As an exogenous protectant, Biodegradable Liquid Film (BLF) is considered to protect winegrapes from low temperatures and dry winds for safe overwintering. This study aimed to reveal the physiological and biochemical mechanisms of BLF regulating the freezing tolerance of wine grapes. Groups of ten-year-old vines (Cabernet Sauvignon) were sprayed with BLF in November 2020 and 2021, or left untreated as a control treatment, and field plant mortality after overwintering were investigated. Branch samples were collected monthly for determination of biochemical indicators. Dormant two-year-old cuttings (Cabernet Sauvignon) were also used for the determination of relative expression levels of key genes. The results showed that the application of BLF reduced the branch semi-lethal temperature in January and February samples compared with control, and reduced the mortality of above-ground parts, branches and buds. The physiological status of shoots was greatly affected by the climatic conditions of the year, but BLF treatment increased the levels of soluble protein and soluble sugar, and also decreased the content of superoxide anion and malondialdehyde at most sampling times. Correlation analysis showed that the differences in freezing tolerance between BLF and no treated overwintering(CK) vines were mainly related to peroxidase activity, soluble sugar, reducing sugar and starch content. Low temperature stress activated the over expression of ICE1, CBF1, and CBF3, especially for 12h. BLF treatment significantly increased the expression levels of CBF1 and CBF3 under low temperature stress. Overall, these results demonstrate that BLF treatment protects vines from freezing damage by upregulating osmo-regulatory substances and alleviating oxidative damage.

MRI of radiation chemistry: First images and investigation of potential mechanisms.

Paramagnetic species such as O2 and free radicals can enhance T1 and T2 relaxation times. If the change in relaxation time is sufficiently large, the contrast will be generated in magnetic resonance images. Since radiation is known to be capable of altering the concentration of O2 and free radicals during water radiolysis, it may be possible for radiation to induce MR signal change. We present the first reported instance of x-ray-induced MR signal changes in water phantoms and investigate potential paramagnetic relaxation enhancement mechanisms associated with radiation chemistry changes in oxygen and free radical concentrations. Images of water and 10 mM coumarin phantoms were acquired on a 0.35 T MR-linac before, during, and after a dose delivery of 80Gy using an inversion-recovery dual-echo sequence with water nullified. Radiation chemistry simulations of these conditions were performed to calculate changes in oxygen and free radical concentrations. Published relaxivity values were then applied to calculate the resulting T1 change, and analytical MR signal equations were used to calculate the associated signal change. Compared to pre-irradiation reference images, water phantom images taken during and after irradiation showed little to no change, while coumarin phantom images showed a small signal loss in the irradiated region with a contrast-to-noise ratio (CNR) of 1.0-2.5. Radiation chemistry simulations found oxygen depletion of -11µM in water and -31µM in coumarin, resulting in a T1 lengthening of 24ms and 68ms respectively, and a simulated CNR of 1.0 and 2.8 respectively. This change was consistent with observations in both direction and magnitude. Steady-state superoxide, hydroxyl, hydroperoxyl, and hydrogen radical concentrations were found to contribute less than 1ms of T1 change. Observed radiation-induced MR signal changes were dominated by an oxygen depletion mechanism. Free radicals were concluded to play a minor secondary role under steady-state conditions. Future applications may include in vivo FLASH treatment verification but would require an MR sequence with a better signal-to-noise ratio and higher temporal resolution than the one used in this study.

Dual RNA and 16S ribosomal DNA sequencing reveal arbuscular mycorrhizal fungi-mediated mitigation of selenate stress in Zea mays L. and reshaping of soil microbiota

Excessively high concentrations of selenium (Se) in soil are toxic to crop plants, and inoculation with arbuscular mycorrhizal fungi (AMF) can reverse Se stress in maize (Zea mays L.). To investigate the underlying mechanisms, maize seedlings were treated with sodium selenate (5 mg Se[VI] kg-1) and/or AMF (Funneliformis mosseae and Claroideoglomus etunicatum). Dual RNA sequencing in mycorrhiza and 16 S ribosomal DNA sequencing in soil were performed. The results showed that Se(VI) application alone decreased plant dry weight, but increased plant Se concentration, total Se content (mainly selenocysteine), and root superoxide content. Inoculation with either F. mosseae or C. etunicatum increased plant dry weight, decreased Se accumulation and selenocysteine proportion, enhanced root peroxidase activity, and alleviated oxidative stress in Se(VI)-treated plants. Inoculation also downregulated the expression of genes encoding Se transporters, assimilation enzymes, and cysteine-rich receptor-like kinases in Se(VI)-stressed plants, similar to plant–pathogen interaction and glutathione metabolism related genes. Conversely, genes encoding selenium-binding proteins and those related to phenylpropanoid biosynthesis were upregulated in inoculated plants under Se(VI) stress. Compared with Se(VI)-free plants, Se tolerance index, symbiotic feedback percentage on plant dry weight, and root colonization rate were all increased in inoculated plants under Se(VI) stress, corresponding to upregulated expression of ‘key genes’ in symbiosis. AMF inoculation increased bacterial diversity, decreased the relative abundances of selenobacteria related to plant Se absorption (e.g., Proteobacteria and Firmicutes), and improved bacterial network complexity in Se(VI)-stressed soils. We suggest that stress-mediated enhancement of mycorrhizal symbiosis contributed to plant Se(VI) tolerance, whereas AMF-mediated reshaping of soil bacterial community structure prevented excessive Se accumulation in maize.

Mechanistic Insights into the Ameliorative Effect of Cichoriin on Diabetic Rats-Assisted with an In Silico Approach.

Rats were allocated into five groups. Group I was considered as the control group, while the other groups were HFD/STZ-induced diabetic rats. Group II was assigned as the diabetic control. Groups III and IV were treated with cichoriin (50 or 100 mg/kg, respectively). Group V received glibenclamide (5 mg/kg) (as a positive control). The blood glucose (BG), serum insulin, triglycerides (TG), total cholesterol (TC), total antioxidant capacity (TAC), catalase, hepatic superoxide dismutase (SOD) and content of malondialdehyde (MDA) were assessed. Histopathological and immunohistochemistry analysis of pancreatic tissue were performed. mRNA and protein expressions of GLUT4, AMPK, and PI3K were estimated. Cichoriin treatment ameliorated HFD/STZ-induced diabetic conditions and mitigated the histopathological characteristics of the pancreas, as well as increasing pancreatic insulin expression. This decreased the levels of BG, TG, TC, and MDA and improved the TAC, catalase and SOD contents. Cichoriin demonstrated upregulation of mRNA and protein expressions of GLUT4, AMPK, and PI3K. The in silico binding of cichoriin with GLUT4, AMPK, and PI3K supported the possible current activities. Collectively, this work highlighted the potential role of cichoriin in mitigating HFD/STZ-induced diabetic conditions and showed it to be a valuable product.

Intercropping of wheat alleviates the adverse effects of phenolic acids on faba bean.

After years of continuous cultivation of faba beans (Vicia faba L.), autotoxic substances accumulate in the soil, leading to a high incidence of Fusarium oxysporum (FOF) wilt. Faba bean-wheat intercropping is often used to alleviate these problems. The goal of this research was to explore the role of benzoic acid and cinnamic acid in promoting the occurrence of faba bean Fusarium wilt and the potential mechanism of faba bean-wheat intercropping to control the occurrence of this disease. We established a field experiment and a hydroponic experiment that involved the inoculation of FOF and the exploration of exogenous addition of cinnamic acid and benzoic acid at different concentrations, the effects on the degree of peroxidation, resistance system, and ultrastructure of faba bean roots. In addition, the antioxidative response of faba bean-wheat intercropping against the autotoxicity of benzoic acid and cinnamic acid was examined. In the field experiment, compared with monoculture, faba bean-wheat intercropping effectively controlled the occurrence of Fusarium wilt, significantly reduced the contents of H2O2 and O2 - in faba bean roots, increased the expression and activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), maintained cell stability, and significantly reduced the contents of benzoic acid and cinnamic acid in faba bean rhizosphere. In the pot experiment, it was found that compared with the control, different concentrations of benzoic acid and cinnamic acid (50, 100, and 200 mg·L-1) significantly increased the content of H2O2 and O2 - in faba bean, decreased the activity and gene expression of antioxidant enzymes SOD and CAT, and damaged cell membrane structure. Furthermore, it promoted the occurrence of Fusarium wilt of faba bean. The faba bean-wheat intercropping alleviated the stress. Benzoic acid and cinnamic acid can increase the content of hydrogen peroxide and superoxide anions in faba bean plants, reduce the enzymatic activity and expression of antioxidant enzyme genes, damage the cell membrane structure, and promote the occurrence of faba bean Fusarium wilt. The faba bean-wheat intercropping can effectively alleviate the autotoxicity of benzoic acid and cinnamic acid and reduce the occurrence of faba bean Fusarium wilt.

Declined photosynthetic nitrogen use efficiency under ammonium nutrition is related to photosynthetic electron transport chain disruption in citrus plants

Nitrogen (N) is an essential nutrient for citrus growth and development. Previously, we identified citrus as an ammonium (as NH4+-N or AN) sensitive plant; however, the mechanism underlying the changes in photosynthetic physiology in response to AN stress remain unclear. ‘Lugan’ (Citrus reticulata Blanco cv. Ponkan) citrus seedlings were sand cultivated in the presence of two forms of N (AN and nitrate as NO3−-N or NN), and three N levels (1, 4 and 8 mmol L−1, as N1, N4 and N8). Biomass, leaf N concentration per unit leaf area (LNC), gas exchange, relative chlorophyll value (SPAD), photosynthetic N use efficiency (PNUE), chlorophyll a fluorescence, reactive oxygen metabolism, and non-structural carbohydrates (NSC) were determined. Compared with NN, AN significantly inhibited the growth of citrus seedlings, accompanied by a reduced net photosynthetic rate at N4 and N8, as well as LNC at N4, with a concomitant decline in PNUE. Leaf NSC, SPAD, light energy absorption and trapping were remarkably elevated by AN, which damaged the oxygen-evolving complex and increased the heat dissipation, resulting in disruption of the photosynthetic electron transport chain. Moreover, increased superoxide anion, H2O2, and malonaldehyde content, and downregulated superoxide dismutase, peroxidase, and catalase activities were also observed in citrus leaves under AN. However, the severity of these adverse effects of AN in citrus plants increased with N levels. Overall, these results indicate that AN supply reduces PNUE by disrupting the photosynthetic electron transport chain, which inhibits the growth of citrus seedlings.

Physiological and gene expression responses of diploid and triploid Pacific oyster ( Crassostrea gigas ) to heat acclimation

High temperature is considered to be one of the important causes of mass mortality of diploid and triploid oysters in summer. In order to compare the tolerance adaptability of diploid and triploid oysters to heat stress, the activities of superoxide dismutase activity (SOD), catalase activity (CAT) and contents of malondialdehyde (MDA) and the expression of Hsp70 and metallothionein (MT) genes in diploid and triploid oysters under acute and chronic heat stress were studied. The results showed that the survival rate of diploid oysters was significantly higher than that of triploid oysters under acute and chronic heat stress (p < 0.05). Under acute heat stress, the SOD levels in gills of both diploid and triploid oysters increased significantly from hour 3 (p < 0.05), but there was no significant difference in SOD levels between diploid and triploid oysters at all time points. The SOD level in hepatopancreas of triploid oysters was significantly higher than that of diploid oysters at all time points except 48 h (p < 0.05). The CAT level of diploid and triploid oysters decreased sharply at 48 h and that of diploid oysters was significantly higher than that of triploid oysters (p < 0.05). Under acute heat stress, the increase in MDA content in triploid oysters was significantly higher than that in diploid oysters (p < 0.05). Under acute heat stress, the expression levels of Hsp70 in the gills and hepatopancreas were significantly increased in diploid and triploid oysters (p < 0.05), but increased varies between gills and hepatopancreas. The expression levels of MT in the gills and hepatopancreas were significantly decreased in diploid and triploid oysters (p < 0.05). The results obtained in this study provide physiological and immunological evidence to explain differences in high-temperature tolerance between diploid and triploid oysters and help us better understand the mass mortality of oysters that occurs during high temperatures in summer.

Heat and drought priming induce tolerance to subsequent heat and drought stress by regulating leaf photosynthesis, root morphology, and antioxidant defense in maize seedlings

Novel stress tolerance strategies, such as heat and drought priming, are widely used in plants to increase tolerance to subsequent stresses. To date, it is still not known whether heat, drought, and combined stress priming can improve the tolerance of maize plants to heat, drought, and combined stresses by improving the morphology and distribution of roots and antioxidant defense mechanisms in maize seedlings. Here, seedlings of maize were firstly twice exposed to heat, drought, and combined stress at 33 °C/25 °C and 50–60% of soil water holding capacity (SWHC) followed by temperature and water recovery, and then subjected to more severe heat, drought, and combined stress at 36 °C/28 °C and 45–55% of SWHC. Under individual heat or drought stress, healthy values of gas exchange and chlorophyll fluorescence parameters, leaf relative water content, leaf water potential, and leaf cooling were significantly reduced, while superoxide anion and MDA contents in roots were significantly increased. Combined heat and drought stress usually exhibit a typical superimposed effect for the abovementioned parameters. Plants with heat, drought, and combined stress priming improved the redox balance of maize roots by enhancing the activities of superoxide dismutase, peroxidase, and catalase, initiated increases in root vitality as well as osmoregulatory substance contents as evidenced by increased soluble sugar, soluble protein, and proline contents. Principal component analysis revealed a strong correlation between antioxidant enzyme activities and osmoregulatory substance contents in roots. The combined stress priming effectively increased total root length, total root surface area, total root volume, and total root dry weight when compared with no priming. Combined stress priming optimized root distribution, leading to an increase in root length density and root dry weight density in the 12–18, 18–24, and 24–30 cm soil layers. Additionally, a strong positive correlation was observed between leaf relative water content, leaf water potential, and leaf cooling, indicating that better leaf water relations in the primed plants were conducive to the improvement of leaf cooling capacity, which provides good conditions for the increase in photosynthetic rate to maintain the integrity of the maize plant. The significant increases in leaf area, specific leaf weight, aboveground dry mass, and a significant reduction in leaf rolling in combined stress-primed plants indicated that the negative effects of heat and drought stress can be effectively mitigated. The current data indicated that the beneficial stress memory induced by priming in maize seedlings developed their defense systems to trigger more effective clearance mechanisms against subsequent combined heat and drought stress. These findings provided evidence that heat, drought, and combined stress priming enhanced maize adaptability to subsequent heat, drought, and combined stress by improving the morphology, distribution, and antioxidant capacity of the root system. • The effects of combined heat and drought stress on leaf water relations, photosynthesis, , and root physiological activities were studied. • Combined stress-primed plants acquired a stress imprint. • The enhanced tolerance of primed plants to heat and drought stress may be attributed to improved physiological activities in roots.

Onion and Apple Functional Ingredients Intake Improves Antioxidant and Inflammatory Status and Vascular Injury in Obese Zucker Rats.

The objective of this study was to investigate the effects of onion and apple functional ingredients in homozygous (fa/fa) obese Zucker rats. Rodents were fed three diets: standard diet [obese control (OC) group], standard diet containing 10% onion [obese onion 10% (OO) group] and standard diet containing 10% apple [obese apple 10% (OA) group] for 8 weeks. Food intake and body weight gain were higher in obese than in lean rats. Food efficiency was lower in OO and AO groups compared with OC group. Within the obese groups, total cholesterol, LDL-cholesterol, triacylglycerols, glucose, insulin and triglyceride-glucose index were lower in OO group than in OC group, and HDL-cholesterol was higher in OO group than in OC group. In general, antioxidant activity (ABTS•+ and FRAP), antioxidant enzyme activities (CAT, SOD, GPx), GSH/GSSG ratio, nitrate/nitrite and GLP-1 increased in OO and OA groups compared with OC. Oxidative stress biomarkers, namely protein carbonyls, 8-hydroxy-2′-deoxyguanosine, 8-epi-prostaglandin F2α, inflammatory and vascular injury biomarkers (PAI-1, TIMP-1, VEGF, sICAM-1, sE-Selectin, MCP-1) and leptin, were lower in OO and OA groups than in OC group. Endothelial impairment was partially reversed, and superoxide content and gene expression of NLRP3, NFKβ1 and COX2 decreased, in OO and OA groups with respect to OC group. The study demonstrates that high pressure-processed onion and apple functional ingredients administration to obese Zucker rats causes beneficial effects on metabolic health, in particular through improving food efficiency ratio; exerting pronounced lipid-lowering effects; reducing glycemia, insulinemia, and biomarkers of hepatic injury (ALT, AST); improving antioxidant, oxidative stress, inflammatory and vascular injury biomarkers, metabolic hormones, and endothelial function; and decreasing proinflammatory gene expression of NLRP3, NFKβ1 and COX2.

Tragacanth gum coating suppresses the disassembly of cell wall polysaccharides and delays softening of harvested mango (Mangifera indica L.) fruit

Mango is a climacteric fruit and is prone to high perishability. The rapid softening and ripening (due to degradation and disassembly of cell wall polysaccharides) are the major limitations in extending the storability of the harvested mango fruits. Various types of gum-based edible coatings have been reported for the shelf life extension of mango fruits. Tragacanth gum (TCG) also has appropriate coating properties. Its use as an edible coating has been reported on certain fruits. However, the effect of TCG coating in the regulation of harvested mango fruits ripening and softening has not been reported yet. So, the objective of this work was to investigate the effect of TCG (control, 0.5 %, 1 % and 1.5 %) coating on postharvest softening and ripening of harvested mango fruits. TCG coating affected the ripening and softening of mango in a dose-dependent manner. Results exhibited that mango fruits coated with 1.5 % TCG showed substantially lower disease incidence and weight loss. The 1.5 % TCG-coated mangoes showed substantially lower ethylene biosynthesis and respiration rate peaks as well as superoxide anion and hydrogen peroxide contents compared with the control. In the same way, 1.5 % TCG-coated mango fruits had markedly higher total chlorophyll content and lower L*, b* and a* along with substantially lower total carotenoids in peel tissues. Mango fruits coated with 1.5 % TCG exhibited markedly lower water-soluble pectin and higher chelate-soluble pectin, Na2CO3-soluble pectin, protopectin, cellulose and hemicellulose in flesh tissues compared with control. The activity of polygalacturonase (PG), cellulase (CX), pectin methylesterase (PME), β-galactosidase (β-Gal) and β-glucosidase (β-Glu) were significantly lower in flesh of 1.5 % TCG treated fruits along with substantially higher firmness in contrast with control. In addition, 1.5 % TCG coating treatment showed significantly higher activity of antioxidative enzymes and delayed the increase in soluble solids content (SSC) and ripening index (RI) along with considerably higher titratable acidity (TA) compared with the untreated control. So, pre-storage TCG based edible coating (1.5 %) could be applied to delay ripening and softening in mango fruit industry under postharvest ambient conditions.