Ascorbic Content Research Articles

WRKY74 regulates cadmium tolerance through glutathione-dependent pathway in wheat.

Cadmium (Cd) is a toxic heavy metal to plants and human health. Ascorbate (ASA)-glutathione (GSH) synthesis pathway plays key roles in Cd detoxification, while its molecular regulatory mechanism remains largely unknown, especially in wheat. Here, we found a WRKY transcription factor-TaWRKY74, and its function in wheat Cd stress is not clear in previous studies. The expression levels of TaWRKY74 were significantly induced by Cd stress. Compared to control, the activities of GST, GR, or APX were significantly increased by 1.55-, 1.43-, or 1.75-fold and 1.63-, 2.65-, or 2.30-fold in shoots and roots of transiently TaWRKY74-silenced wheat plants under Cd stress. Similarly, the contents of hydrogen peroxide (H2O2), malondialdehyde (MDA), GSH, or Cd were also significantly increased by 2.39- or 1.25-fold, 1.54- or 1.20-fold, and 1.34- or 5.94-fold in shoots or roots in transiently TaWRKY74-silenced wheat plants, while ASA content was decreased by 47.4 or 43.3% in shoots, 10.7 or 6.5% in roots in these silenced wheat plants, respectively. Moreover, the expression levels of GSH, GPX, GR, DHAR, MDHAR, and APX genes, which are involved in ASA-GSH synthesis, were separately induced by 2.42-, 2.16-, 3.28-, 2.08-, 1.92-, and 2.23-fold in shoots, or by 10.69-, 3.33-, 3.26-, 1.81-, 16.53-, and 3.57-fold in roots of the BSMV-VIGS-TaWRKY74-inoculated wheat plants, respectively. However, the expression levels of TaNramp1, TaNramp5, TaHMA2, TaHMA3, TaLCT1, and TaIRT1 metal transporters genes were decreased by 21.2-76.3% (56.6%, 59.2%, 76.3%, 53.6%, 35.8%, and 21.2%) in roots of the BSMV-VIGS-TaWRKY74-inoculated wheat plants. Taken together, our results suggested that TaWRKY74 alleviated Cd toxicity in wheat by affecting the expression of ASA-GSH synthesis genes and suppressing the expression of Cd transporter genes, and further affecting Cd uptake and translocation in wheat plants.

Functional Properties and Preservative Effect of P-Hydroxybenzoic Acid Grafted Chitosan Films on Fresh-Cut Jackfruit.

In the present study, p-hydroxybenzoic acid-grafted chitosan (PA-g-CS) conjugates with different grafting degrees were synthesized by a free radical-regulated grafting approach. The conjugates were further developed into films by casting, and their characteristics and preservative effects on fresh-cut jackfruit were evaluated. Compared to the CS film, the PA-g-CS film showed comprehensive performance improvements, including enhancements of water solubility, anti-ultraviolet capacity, antioxidation, and antibacterial activity. Moreover, compared with CS film, some appreciable and favorable changes of physical properties were observed in the PA-g-CS films, which included water vapor permeability, oxygen permeability, surface morphology, moisture content, and mechanical intensity. Furthermore, compared to CS alone, the application of PA-g-CS films to fresh-cut jackfruit exerted a beneficial effect on the quality of products, as indicated by the inhibition of weight loss, softening, and membrane damage, the maintenance of soluble solids and ascorbic acids contents, as well as a reduced bacterial count and a higher sensory score. Among these PA-g-CS films, the best preservation effect was achieved with the highest degree of grafting (PA-g-CS III). The results suggested that the PA-g-CS film has the potential to be explored as a new type of packaging material for the preservation of fresh-cut fruits and vegetables.

Metabolism of carbohydrates and activity of the antioxidant system in mosses on a post-technogenic salinized territory

Adaptive physiological and biochemical reactions of mosses Didymodon rigidulus Hedw., Barbula unguiculata Hedw. and Brachythecium campestre (Müll. Hal.) Schimp. to salt stress have been investigated from the territory of the tailings storage of the Stebnyk Mining and Chemical Enterprise “Polymineral” (Lviv region, Ukraine). The peculiarities of carbohydrate metabolism in mosses under salinity conditions have been studied. The content of soluble carbohydrates and proline, the antioxidant activity, the content of ascorbate and reduced glutathione as well as the activity of enzymes of their metabolism – ascorbate peroxidase and glutathione reductase at the initial stages of the stress (salt shock) and prolonged stress exposure (salt stress) have been evaluated. It has been found that the increase of α-amylase activity, enhancement of the hydrolysis of starch and the increase of the concentration of soluble carbohydrates under salt stress were the reactions of the studied species of mosses. It has been established that there was an increase in the concentration of soluble carbohydrates by 1.2–1.5 times in moss shoots under salinity conditions, compared with plants from the background area (vicinity of Stebnyk). Experimental studies have shown that under salinity conditions sucrose dominates in the pool of soluble carbohydrates (59.0–79.5% of the total sugars content). The sucrose content was 1.5–2.0 times higher in the plants B. unguiculata and D. rigidulus from the highly saline area of the tailings storage. It has been indicated that under stress conditions constitutive adaptive mechanisms are more expressed in resistant moss species, and plants with a lower level of resistance adapt to the stressor, mainly due to induced protective systems. Experimental studies have shown that plants B. unguiculata and D. rigidulus, which are resistant to abiotic stressors, have a high constitutive pool of soluble carbohydrates both at the beginning of the experiment and under prolonged exposure of the salt stress. In the shoots of the sensitive moss B. campestre the stress-induced character of the sugars accumulation has been revealed. The accumulation of proline in mosses cells under salt stress depended on their species characteristics. The stress-induced accumulation of proline can be considered as a part of the bryophytes’ protective system, but this osmolyte does not play a key role in the formation of the mosses’ resistance to salt stress. Obviously, soluble carbohydrates are the main osmolytes in the moss cells. It has been found that resistant moss species have a high constitutive antioxidant status, while in the sensitive moss B. campestre the increase in the antioxidant activity occurred during prolonged salt stress, which may indicate its induced nature. It has been shown that the resistant mosses B. unguiculata and D. rigidulus have 3–4 times higher levels of glutathione and ascorbate content and 1.6–2.5 times higher activity of enzymes of their metabolism – glutathione reductase and ascorbate peroxidase, compared to plants of the less tolerant moss species B. campestre, which provided reduction of the lipid peroxidation process in plasma membranes and decreased the content of TBA-active products under stress.

Iron oxide nanoparticles and selenium supplementation improve growth and photosynthesis by modulating antioxidant system and gene expression of chlorophyll synthase (CHLG) and protochlorophyllide oxidoreductase (POR) in arsenic-stressed Cucumis melo

Current research reveals the positive role of iron oxide nanoparticles (IONPs) and selenium (Se) in extenuation of arsenic (As) induced toxicity in Cucumis melo. C. melo plants grown in As spiked soil (20 mg kg−1 As) showed reduced growth, chlorophyll (Chl) content, photosynthetic rate, stomatal conductivity and transpiration. On the other hand, the alone applications of IONPs or Se improved growth and physiochemical parameters of C. melo plants. Additionally, exogenous application IONPs and Se synergistically improved the activity of antioxidative enzymes and glyoxalase system in C. melo plants. In addition, the collective treatment of IONPs and Se reduced As uptake, enhanced rate of photosynthesis and increased gas exchange attributes of C. melo plants under As stress. Interactive effect of IONPs and Se regulated reduced glutathione (GSH), oxidized glutathione (GSSG) and ascorbate (AsA) content in C. melo plants exposed to As-contaminated Soil. IONPs and Se treatment also regulated expression of respiratory burst oxidase homologue D (RBOHD) gene, chlorophyll synthase (CHLG) and protochlorophyllide oxidoreductase (POR). Therefore, the combined treatment of IONPs and Se may enhance the growth of crop plants by alleviating As stress.

Simultaneous quantification of peroxidase/ascorbate in vegetables with slope and intercept of kinetic curves in a flow-injection recirculating-catalysis system

In using a flow-injection recirculating-catalysis system developed by us to research the simultaneous quantification for peroxidase and ascorbate, it was discovered that the concentrations of peroxidase activity and ascorbate are correlative with the slope and the negative intercept of the linear response curve during a peroxidase-catalyzed kinetic course. Therefore, based on this finding, a new analytical method and a simplified equation for quantifying the peroxidase activity concentration were proposed, Then, test conditions were optimized, finally the use of the method has realized the simultaneous determination for peroxidase of 2–40 U/L and ascorbate of 0.4–12 mg/L in various vegetables (60 μL). The assayed results were consistent with the comparison method, in which the repeatability (RSD < 1.43%, n = 11) was satisfactory. Another important conclusion obtained in this study is that the determination of the peroxidase activity in biosamples must use the kinetic curve method for fear of the influence from the ascorbate’s lag phase.

Hypothesis: Mutual dependency of ascorbate and calcidiol for optimal performance of the immune system

For a proper functioning, immune cells require sufficient levels of ascorbate and calcidiol in the blood. Upon activation, immune cells increase their internal conversion of calcidiol to calcitriol. In general, calcitriol can affect the expression of ca. 3% of the genes in the human genome. Among the gene products are a number of Fe(II)- and 2-oxoglutarate-dependent dioxygenases functioning as demethylases of histones, DNA, RNA and ribosomes in epigenetic gene regulation. These dioxygenases require millimolar concentrations of ascorbate for activity. Immune cells contain 1–4 mM ascorbate. It is hypothesized here that there is a mutual dependency of ascorbate and calcidiol for optimal performance of the human immune system. Early signs for this thesis are in literature, but were not yet recognized. Daily intake of both compounds to keep the plasma levels to ca. 75 µM for ascorbate and to at least 75 nM for calcidiol, will reduce the risk of serious disease after infections. This applies in particular to infected individuals with prolonged elevated levels of neutrophils. Reports state that such subjects are often deficient in either ascorbate (vitamin C) or calcidiol (vitamin D3), but none of the studies considered the levels of both at the same time.

Development of a Genome-Edited Tomato With High Ascorbate Content During Later Stage of Fruit Ripening Through Mutation of SlAPX4.

Ascorbate is an essential antioxidant substance for humans. Due to the lack of ascorbate biosynthetic enzyme, a human must intake ascorbate from the food source. Tomato is one of the most widely consumed fruits, thus elevation of ascorbate content in tomato fruits will improve their nutritional value. Here we characterized Solanum lycopersicum ASCORBATE PEROXIDASE 4 (SlAPX4) as a gene specifically induced during fruit ripening. In tomatoes, ascorbate accumulates in the yellow stage of fruits, then decreases during later stages of fruit ripening. To investigate whether SlAPX is involved in the decrease of ascorbate, the expression of SlAPXs was analyzed during fruit maturation. Among nine SlAPXs, SlAPX4 is the only gene whose expression was induced during fruit ripening. Mutation of SlAPX4 by the CRISPR/Cas9 system increased ascorbate content in ripened tomato fruits, while ascorbate content in leaves was not significantly changed by mutation of SlAPX4. Phenotype analysis revealed that mutation of SlAPX4 did not induce an adverse effect on the growth of tomato plants. Collectively, we suggest that SlAPX4 mediates a decrease of ascorbate content during the later stage of fruit ripening, and mutation of SlAPX4 can be used for the development of genome-edited tomatoes with elevated ascorbate content in fruits.

PSV-8 Effects of Injectable Vitamin C Immediately Prior to Transit Before Slaughter on Meat Color

Abstract The objective was to evaluate the effects of injectable vitamin C (VC) at transit before slaughter on meat color. The prevalence of dark-cutting beef can be exacerbated by transit and environmental conditions resulting in a less desirable product to consumers. Angus × Simmental steers (n = 48; BW = 670 ± 47 kg) were utilized in a completely randomized design. Steers were stratified by BW within pen and randomly assigned to 1 of 2 treatments: an intramuscular injection of saline immediately prior to transit (CON), or an intramuscular injection of VC (15 g sodium ascorbate) immediately prior to transit (VITC). Blood was collected prior to treatment injection to assess plasma ascorbate status. Following pre-transit treatment injections, steers were transported for approximately 6 h (639 km) and slaughtered at a commercial abattoir. At 24 h postmortem, surface color readings were measured using a HunterLab Miniscan EZ spectrophotometer and marbling scores were evaluated on the left and right longissimus muscle. Data were analyzed using the MIXED and GLIMMIX procedures of SAS 9.4 with fixed effects of treatment, truck, and sire, and random effect of carcass side. Pre-transit plasma ascorbate, body weight, and marbling score were used as covariates. No treatment differences were observed for L* (lightness), a* (redness), and b* (yellowness) values (P &amp;gt; 0.16). Hue angle, saturation index, and prevalence of dark cutters (6% of total carcasses) were not affected by treatment (P &amp;gt; 0.78). Initial plasma ascorbate concentrations did not differ between treatments (P = 0.85) but increased with BW (r = 0.39; P ≤ 0.01). Body weight was correlated (r=0.24 to 0.28; P &amp;lt; 0.02) with HunterLab L*, a*, b*, and saturation index values. Overall, injectable VC administered prior to transit to a harvest facility did not impact meat color of beef steers 24 h postmortem.

Soaking Maize Seeds in Zeatin-Type Cytokinin Biostimulators Improves Salt Tolerance by Enhancing the Antioxidant System and Photosynthetic Efficiency.

There is an urgent need for innovative strategies to raise the performance of environmentally stressed plants. The seeds of single-cross yellow Zea mays (L.) hybrid Giza-168 were soaked in Cis-(c-Z-Ck) or trans-zeatin-type cytokinin (t-Z-Ck) solutions at a concentration of 50 or 40 µM, respectively. Salinity stress was imposed at 0, 75 or 150 mM NaCl in the Hoagland nutrient solution (full strength) used for irrigation. The total carotenoids content was negatively affected by only 150 mM NaCl, while both 75 and 150 mM NaCl negatively affected the growth and yield components, relative water content, membrane stability index, photochemical activity, gas exchange, K+ and chlorophyll contents, K+/Na+ ratio, and photosynthetic efficiency. However, all of these traits were significantly improved by c-Z-Ck pretreatment and further enhanced by t-Z-Ck pretreatment compared with the corresponding controls. Furthermore, the contents of proline, soluble sugars, ascorbate, and glutathione, as well as enzymatic antioxidant activities, were significantly elevated by both salt stress concentrations and increased more by both biostimulators compared to the control. Compared to c-Z-Ck, t-Z-Ck was superior in mitigating the harmful effects of the high H2O2 levels caused by salt stress on the levels of malondialdehyde and ion leakage compared to the control. Under normal or stress conditions, t-Z-Ck pretreatment was better than c-Z-Ck pretreatment, while both positively affected maize hormonal contents. As a result, t-Z-Ck is recommended to enhance the growth and productivity of maize plants by suppressing the effects of oxidative stress caused by saline water irrigation.

Pre-Steady-State Reactivity of Peptidylglycine Monooxygenase Implicates Ascorbate in Substrate Triggering of the Active Conformer.

Peptidylglycine monooxygenase (PHM) is essential for the posttranslational amidation of neuroendocrine peptides. An important aspect of the PHM mechanism is the complete coupling of oxygen reduction to substrate hydroxylation, which implies no oxygen reactivity of the fully reduced enzyme in the absence of peptidyl substrates. As part of studies aimed at investigating this feature of the PHM mechanism, we explored pre-steady-state kinetics using chemical quench (CQ) and rapid freeze-quench (RFQ) studies of the fully reduced ascorbate-free PHM enzyme. First, we confirmed the absence of Cu(I)-enzyme oxidation by O2 at catalytic rates in the absence of peptidyl substrate. Next, we investigated reactivity in the presence of the substrate dansyl-YVG. Surprisingly, when ascorbate-free di-Cu(I) PHM was shot against oxygenated buffer containing the dansyl-YVG substrate, <15% of the expected product was formed. Substoichiometric reactivity was confirmed by stopped-flow and RFQ EPR spectroscopy. Product generation reached a maximum of 70% by the addition of increasing amounts of the ascorbate cosubstrate in a process that was not the result of multiple turnovers. FTIR spectroscopy of the Cu(I)-CO reaction chemistry was then used to show that increasing ascorbate concentrations correlated with a substrate-induced Cu(I)M-CO species characteristic of an altered conformation. We conclude that ascorbate and peptidyl substrate work together to induce a transition from an inactive to an active conformation and suggest that the latter may represent the "closed" conformation (Cu-Cu of ∼4 Å) recently observed for both PHM and its sister enzyme DBM by crystallography.

Effects of Azorhizobium caulinodans and Piriformospora indica Co-Inoculation on Growth and Fruit Quality of Tomato (Solanum lycopersicum L.) under Salt Stress

Salt stress is a worldwide environmental signal, reducing the growth and yield of crops. To improve crop tolerance to salt, several beneficial microbes are utilized. Here, nitrogen-fixing bacterium Azorhizobium caulinodans and root endophytic fungus Piriformospora indica were used to inoculate tomato (Solanum lycopersicum) under salt stress, and the effects of the co-inoculation were investigated. Results showed that A. caulinodans colonized in the intercellular space in stems and roots of tomato plants, while P. indica colonized in the root cortex. Two weeks following salt treatment, co-inoculated tomato plants grew substantially taller and had larger stem base diameters. Activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and reduced and oxidized ascorbate and glutathione (i.e., AsA, DHA, GSH, and GSSG, respectively) concentrations along with the ratios of AsA/(AsA + DHA) and GSH/(GSH + GSSG) increased in the leaves of co-inoculated plants under salt stress. The co-inoculation significantly increased soluble proteins and AsA in fruits; however, concentrations of soluble sugars and proanthocyanins did not show significant changes, compared with NaCl only treatment. Data suggest that A. caulinodans and P. indica co-inoculation boosted tomato growth and improved the quality of tomato fruits under salt stress. O-inoculation of A. caulinodans and P. indica might be employed to enhance tomato plant salt tolerance.

Increased Ascorbate Content of Glioblastoma Is Associated With a Suppressed Hypoxic Response and Improved Patient Survival.

Glioblastoma multiforme is a challenging disease with limited treatment options and poor survival. Glioblastoma tumours are characterised by hypoxia that activates the hypoxia inducible factor (HIF) pathway and controls a myriad of genes that drive cancer progression. HIF transcription factors are regulated at the post-translation level via HIF-hydroxylases. These hydroxylases require oxygen and 2-oxoglutarate as substrates, and ferrous iron and ascorbate as cofactors. In this retrospective observational study, we aimed to determine whether ascorbate played a role in the hypoxic response of glioblastoma, and whether this affected patient outcome. We measured the ascorbate content and members of the HIF-pathway of clinical glioblastoma samples, and assessed their association with clinicopathological features and patient survival. In 37 samples (37 patients), median ascorbate content was 7.6 μg ascorbate/100 mg tissue, range 0.8 – 20.4 μg ascorbate/100 mg tissue. In tumours with above median ascorbate content, HIF-pathway activity as a whole was significantly suppressed (p = 0.005), and several members of the pathway showed decreased expression (carbonic anhydrase-9 and glucose transporter-1, both p < 0.01). Patients with either lower tumour HIF-pathway activity or higher tumour ascorbate content survived significantly longer than patients with higher HIF-pathway or lower ascorbate levels (p = 0.011, p = 0.043, respectively). Median survival for the low HIF-pathway score group was 362 days compared to 203 days for the high HIF-pathway score group, and median survival for the above median ascorbate group was 390 days, compared to the below median ascorbate group with 219 days. The apparent survival advantage associated with higher tumour ascorbate was more prominent for the first 8 months following surgery. These associations are promising, suggesting an important role for ascorbate-regulated HIF-pathway activity in glioblastoma that may impact on patient survival.

The Effects of Surgery on Leukocyte Vitamin C Concentrations: A Systematic Review and Meta-Analysis

Abstract Background Vitamin C (ascorbic acid) is a micronutrient imperative for many bodily functions, with research revealing its functional support of leukocytes. The purpose of this meta-analysis was to determine the effects of surgery on leukocyte vitamin C concentrations by assessing the amount and longevity of post-operative leukocyte vitamin C change. Data Sources We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library databases for relevant research papers. Studies were included until January 2022, with no time limits. Studies that reported means and standard deviations of leukocyte/buffer layer vitamin C concentrations before and after surgery were included into the meta-analysis. The meta-analysis comprised of eight studies. Results Seven studies (which included 8 individual studies) were included into our meta-analysis. Combined data from the meta-analysis displayed a significant depletion in mean leukocyte vitamin C concentrations during the first 24 hours following the surgery by a mean of 5.37 µg/108 (32.3%) (CI = -6.35, -4.40) (n = 6, p &lt; 0.001) and during the first post-operative week by 4.43 µg/108 (23%) (-7.27, -1.58) (n = 7, p &lt; 0.001). However, this depletion was followed by an uprise in mean ascorbic acid leukocyte concentrations of 0.93 µg/108 (4.8%) (-0.79, 2.66) (n = 6, p = 0.29) at 7 days (or beyond) post-operatively. Conclusion Significant post-operative leukocyte vitamin C depletions were particularly observed during the first post-operative week. Further research is required to validate the observed results and to determine whether the observed depletions may be linked to compromised immunological function and pathophysiologies that arise during the post-operative period.

Metabolome of Ceratodon purpureus (Hedw.) Brid., a cosmopolitan moss: the influence of seasonality.

Ceratodon purpureus showed changes in disaccharides, flavonoids, and carotenoids throughout annual seasons. These changes indicate harsher environmental conditions during the dry period, directing metabolic precursors to enhance the antioxidant system. Bryophytes are a group of land plants comprising mosses (Bryophyta), liverworts (Marchantyophyta), and hornworts (Antocerotophyta). This study uses the molecular networking approach to investigate the influence of seasonality (dry and rainy seasons) on the metabolome and redox status of the moss Ceratodon purpureus (Hedw.) Brid., from Campos do Jordão, Brazil. Samples of C. purpureus were submitted to three extraction methods: 80% methanol producing the soluble fraction (intracellular compounds), followed by debris hydrolysis using sodium hydroxide producing the insoluble fraction (cell wall conjugated compounds), both analyzed by HPLC-MS; and extraction using pre-cooled methanol, separated into polar and non-polar fractions, being both analyzed by GC-MS. All fractions were processed using the Global Natural Product Social Molecular Network (GNPS). The redox status was assessed by the analysis of four enzyme activities combined with the analysis of the contents of ascorbate, glutathione, carotenoids, reactive oxygen species (ROS), and malondialdehyde acid (MDA). During the dry period, there was an increase of most biflavonoids, as well as phospholipids, disaccharides, long-chain fatty acids, carotenoids, antioxidant enzymes, ROS, and MDA. Results indicate that C. purpureus is under harsher environmental conditions during the dry period, mainly due to low temperature and less water availability (low rainfall).

Determination of some physiological parameters in spinach (Spinacia oleracea L.) cultivated in Kosovo

Summary The objective of this work was to investigate the levels of photosynthetic pigments, antioxidant enzyme activities (superoxide dismutase [SOD], catalase [CAT], peroxidase [POX], ascorbate peroxidase [APX], glutathione reductase [GR], and MDA), total glutathione (GSH), total ascorbate (AsA), and lipid peroxidation of two spinach cultivars (Clipper and Matador) sampled in different locations in Kosovo (Prizren, Ferizaj, and Obiliq). The photosynthetic pigments, chlorophyll a and b as well as carotenoids, were extracted by 80% acetone, and concentrations were calculated based on the absorbance values at 663, 645, and 480 nm. There was a significant difference in SOD, APX, and GR activities between varieties at each location. The MDA and AsA contents in Obiliq were the highest, compared to other locations. From the increase in lipid peroxidation level, it can be assumed that the degradation in pigment content was caused by the decrease in total AsA content and APX and GR enzyme activities, which are the main enzymes of the AsA–GSH cycle in chloroplasts.

Hydrogen Sulfide Interacts with 5-Aminolevulinic Acid to Enhance the Antioxidant Capacity of Pepper (Capsicum annuum L.) Seedlings under Chilling Stress

5-Aminolevulinic acid (ALA) is the precursor of tetrapyrrole synthesis, and hydrogen sulfide (H2S) is a gas signal molecule. Studies have shown that exogenous ALA and H2S can alleviate abiotic stress. This study evaluated the roles of ALA and H2S and their interactions in regulating antioxidant activity in pepper seedlings under chilling stress. Chilling stress significantly inhibited the growth of pepper seedlings and increased the amounts of hydrogen peroxide (H2O2), superoxide anion (O2•−), and malondialdehyde (MDA). ALA and/or H2S increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Moreover, ALA and/or H2S enhanced the ascorbate (AsA)-glutathione (GSH) cycle by increasing the contents of AsA and GSH, the ratio of AsA to dehydroascorbic acid and GSH to glutathione disulfide increased, and the activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) also increased. At the transcriptional level, ALA and/or H2S upregulated the expressions of CaSOD, CaPOD, CaCAT, CaAPX, CaGR, CaDHAR, and CaMDHAR in seedlings under chilling stress. ALA and/or H2S also reduced the contents of H2O2, O2•− and MDA, eventually mitigating the inhibitory effects of chilling stress on pepper seedling growth. The combination of ALA and H2S had a better effect than ALA or H2S alone. Moreover, ALA and H2S interact to regulate the oxidative stress response of pepper seedlings under chilling stress.

Integrative NPK soil and foliar application improves growth, yield, antioxidant, and nutritional status of Capsicum annuum L. in sandy soils under semi-arid condition

Soils of arid and semi-arid environments are characterized by scant moisture conditions, low clay and organic matter contents, low water holding capacity and low inherent fertility, and hence various management practices including foliar fertilization is essential. The present study aims at assessing the effect of integrated soil and foliar application of nitrogen, phosphorus, and potassium (NPK) fertilizers on growth, yield, and contents of some osmoprotectants, antioxidant, and nutritional status of Capsicum annuum (L.) in sandy soil under semi-arid condition. A pot experiment was conducted with five NPK application treatments: 100% added to the soil + 0% foliar spray, 75% soil + 25% foliar spray, 50% soil + 50% foliar spray, 25% soil + 75% foliar spray, and 0% soil + 100% foliar spray. The results of the study indicate that the integrated treatment of 50% soil + 50% foliar spray proved to be the best treatment compared with other treatments. This treatment significantly increased growth components (leaf area plant‒1, shoot fresh and dry weights) and yield (number of fruits plant‒1, average fruit weight, and fruits weight plant‒1), and the contents of soluble sugars, free proline, and nutrients (NPK); while significantly reduced the contents of ascorbate and glutathione compared to other treatments, including the control. The combined treatment of 75% soil + 25% foliar spray was the second-best treatment with respect to all tested parameters. The study concludes that the recommend integrated treatment of 50% soil + 50% foliar spray minimizes nutrient loss and achieves higher growth and yield of hot pepper plants under semi-arid condition.

Inuloxin A Inhibits Seedling Growth and Affects Redox System of Lycopersicon esculentum Mill. and Lepidium sativum L.

Allelochemicals are considered an environment-friendly and promising alternative for weed management, although much effort is still needed for understanding their mode of action and then promoting their use in plant allelopathy management practices. Here, we report that Inuloxin A (InA), an allelochemical isolated from Dittrichia viscosa, inhibited root elongation and growth of seedlings of Lycopersicon esculentum and Lepidium sativum at the highest concentrations tested. InA-induced antioxidant responses in the seedlings were investigated by analysing the contents of glutathione (GSH) and ascorbate (ASC), and their oxidized forms, dehydroascorbate (DHA), and glutathione disulphide (GSSG), as well as the redox state of thiol-containing proteins. An increase in ASC, DHA, and GSH levels at high concentrations of InA, after 3 and 6 days, were observed. Moreover, the ASC/DHA + ASC and GSH/GSSG + GSH ratios showed a shift towards the oxidized form. Our study provides the first insight into how the cell redox system responds and adapts to InA phytotoxicity, providing a framework for further molecular studies.

Biochemical compounds and stress markers in lettuce upon exposure to pathogenic Botrytis cinerea and fungicides inhibiting oxidative phosphorylation

Main conclusionBotrytis cinerea and fungicides interacted and influenced selected biochemical compounds. DPPH and glutathione are the first line of defence against biotic/abiotic stress. Plant metabolites are correlated with fungicides level during dissipation.Botrytis cinerea is an etiological agent of gray mould in leafy vegetables and is combated by fungicides. Fluazinam and azoxystrobin are commonly used fungicides, which inhibit oxidative phosphorylation in fungi. In this study, lettuce was (i) inoculated with B. cinerea; (ii) sprayed with azoxystrobin or fluazinam; (iii) inoculated with B. cinerea and sprayed with fungicides. This investigation confirmed that B. cinerea and fungicides affected lettuce’s biochemistry and stress status. B. cinerea influenced the behaviour of fungicides reflected by shortened dissipation of azoxystrobin compared to non-inoculated plants, while prolonged degradation of fluazinam. Stress caused by B. cinerea combined with fungicides reduced level of chlorophylls (53.46%) and carotenoids (75.42%), whereas increased phenolic compounds (81%), ascorbate concentrations (32.4%), and catalase activity (116.1%). Abiotic stress caused by fungicides contributed most to the induction of carotenoids (107.68 µg g−1 on dissipation day 3−1). Diphenyl picrylhydrazyl (DPPH) radical scavenging activity and glutathione concentration peaked from the first hour of fungicides dissipation. For the first time correlation between the status of plant metabolites and fungicides during their dissipation was observed. These results indicate that non-enzymatic antioxidants could be the first-line compounds against stress factors, whereas ascorbate and antioxidant enzymes tend to mitigate stress only secondarily. The findings of this study help better understand plant biochemistry under biotic/abiotic stress conditions.

Oviposition behaviour and biochemical response of an insect pest, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae) to plant phenolic compound phloroglucinol

Phenolic compounds are the secondary metabolites (SMs) present in plants carrying different bioactivities. In the present study, we explored the influence of a phenolic compound namely phloroglucinol on oviposition behaviour and different biochemical entities of an insect pest Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae) using artificial diet. Phloroglucinol (IUPAC name: benzene-1,3,5-triol) affected the activity of antioxidant and detoxifying enzymes viz. superoxide dismutases (SOD), catalase (CAT), ascorbate peroxidases (APOX). dehydroascorbate reductase (DHAR), peroxidases (POX), phenol oxidase (PO), glutathione peroxidase (GPOX), glutathione S-transferase peroxidase (GSTpox), glutathione reductase (GR), glutathione S-transferase (GST) and esterases (EST) as well as the biological antioxidants viz. ascorbate content and glutathione. The lipid peroxide content (LP) and hydrogen peroxide content (H2O2) were significantly enhanced in the treated larvae indicating oxidative stress in the insect. Significant inhibition in oviposition was observed and effective repellency percentage increased with phloroglucinol treatment as compared to control. The oviposition deterrent activity and toxic effects of phloroglucinol on various biochemical parameters of Z. cucurbitae larvae revealed in the present study clearly confirms its suitability for use in pest management.