The role of ascorbate peroxidase, guaiacol peroxidase, and polysaccharides in cassava ( Manihot esculenta Crantz) roots under postharvest physiological deterioration

Integrating physiological, metabolome and transcriptome revealed the response of maize seeds to combined cold and high soil moisture stresses

Combined cold and high moisture stress (CHS) is a prevalent abiotic stress during maize sowing in northeast China, severely affecting the growth of seedlings and seed germination. However, the mechanism underlying seed growth responses to CHS remains unclear. We used Jidan441 (JD441, CHS-resistant) and Jidan558 (JD558, CHS-sensitive) as experimental materials. Treatments of 5-day cold (4°C, CS), high moisture (25%, gravimetric water content, HH), and CHS were initiated at sowing, followed by a return to normal growth conditions (20°C during light/ 15°C during dark, 15%) at 7 days after sowing (DAS). CS, HH, and CHS decreased seed root length and surface area. The reduction in root length and surface area in JD441 due to CHS was less severe than in JD558. We found that the difference between CHS and control in JD441was less than that in JD558 at transcriptional and metabolic levels at 7 DAS. After CHS removal, JD441 exhibited a greater increase in α-amylase activity and antioxidant content than JD558, which facilitated starch decomposition and the rapid removal of O2 - and H2O2 in seeds. The rapid recovery of soluble sugar and soluble protein in JD441 helped maintain osmotic balance. Amino acids and genes related to amino acid metabolism were upregulated in response to combined stress in JD441, whereas they were downregulated in JD558. In conclusion, the stress tolerance of JD441 was attributed to its efficient recovery ability from CHS. This study provides a scientific foundation for exploring seed stress tolerance pathways and developing cold and high-moisture-tolerant hybrids.

Physiological and Microstructure Analysis Reveals the Mechanism by Which Formic Acid Delays Postharvest Physiological Deterioration of Cassava

Formic acid is reported to act as a food preservative and feed additive, but its effects on controlling postharvest physiological deterioration (PPD) development in cassava are unclear. In this study, we assessed the effectiveness of different concentrations of formic acid in attenuating PPD occurrence in fresh-cut cassava. The results showed that the concentration of 0.1% (v/v) formic acid could significantly delay the occurrence of PPD, and that the higher the concentration of formic acid supplied, the later the occurrence of PPD symptoms. The physiological and biochemical analysis of 0.5%-formic-acid-treated cassava slices revealed that formic acid decreased the degradation of starch, inhibited the accumulation of hydrogen peroxide (H2O2), malondialdehyde (MDA), and water-soluble pectin in cassava slices with PPD development, and increased the activities of the antioxidant enzymes ascorbate peroxidase (APX) and glutathione reductase (GR). A microscopic observation showed that the formic acid treatment inhibited the enlargement of the intercellular space during the cassava PPD process, which suggests that the formation of an intercellular layer of the cell wall was inhibited by formic acid. This study thus revealed the mechanism used by formic acid to extend the cassava shelf life; however, a detailed evaluation of the possible side effects on, for example, the cyanide content will be needed to categorically ensure the safety of this method.

Foliar applications of zinc oxide nanoparticles and boric acid affect leaf oxidative metabolism and productivity in young pecan trees

Zinc and boron are nutrients that often suffer low bioavailability to pecan trees grown in calcareous soils whereas adequate supplies of these two elements is essential for commercial pecan production. Working with young pecan trees, we evaluated changes in oxidative metabolism, levels of bioactive compounds, yield components and foliar nutrient concentrations in response to foliar sprays (50 or 100 mg L-1) of zinc oxide nanoparticles (ZnO NPs) and boron (H3BO3). Four different treatment solutions were applied in a completely randomised design with six replications per treatment (24 trees in total). Zinc and B treatments were applied before pistil receptivity (3 weeks before anthesis) and at stem elongation stage 31, 39/60; flowering stage 69; fruit stages 7-75 and continued for a total of five applications at 14-day intervals. We evaluated enzyme activities (SOD, H2O2, CAT and GPx), AC, phenols, flavonoids, leaf area, chlorophyll, total anthocyanins and nut yield and quality (nut weight and % kernel). The mineral concentrations in the leaflets were also determined. The mineral concentrations (N, P, K, Ca, Mg, Fe, Cu, Mn, Ni, Zn and B) in the leaflets were also determined. Spraying ZnO NPs and B increased SOD activity, CA, chlorophyll concentration, mineral nutrients (N, K, Ca, Zn and B) and yield. However, reductions were observed for CAT activity, nut quality and concentrations of phenol, flavonoid, anthocyanin and Fe. Boron increased GPx activity and P concentration. These results demonstrate that spraying low doses (50 mg L-1) of ZnO NPs and B can help reduce oxidative stress and increase yield, nut quality and leaf concentrations of Zn and B in young cv. Wichita pecan trees established on a calcareous soil.

CRISPR/Cas9: an advanced platform for root and tuber crops improvement

Root and tuber crops (RTCs), which include cassava, potato, sweet potato, and yams, principally function as staple crops for a considerable fraction of the world population, in addition to their diverse applications in nutrition, industry, and bioenergy sectors. Even then, RTCs are an underutilized group considering their potential as industrial raw material. Complexities in conventional RTC improvement programs curb the extensive exploitation of the potentials of this group of crop species for food, energy production, value addition, and sustainable development. Now, with the advent of whole-genome sequencing, sufficient sequence data are available for cassava, sweet potato, and potato. These genomic resources provide enormous scope for the improvement of tuber crops, to make them better suited for agronomic and industrial applications. There has been remarkable progress in RTC improvement through the deployment of new strategies like gene editing over the last decade. This review brings out the major areas where CRISPR/Cas technology has improved tuber crops. Strategies for genetic transformation of RTCs with CRISPR/Cas9 constructs and regeneration of edited lines and the bottlenecks encountered in their establishment are also discussed. Certain attributes of tuber crops requiring focus in future research along with putative editing targets are also indicated. Altogether, this review provides a comprehensive account of developments achieved, future lines of research, bottlenecks, and major experimental concerns regarding the establishment of CRISPR/Cas9-based gene editing in RTCs.

Response of cassava (Manihot esculenta Crantz) genotypes to natural infestation by scale insect pest Stictococcus vayssierei Richard (Hemiptera: Stictococcidae)

Cassava is mostly grown for its starchy roots, which ensure food security. However, it is heavily attacked by the African root and tuber scale (ARTS) Stictococcus vayssierei in Central Africa. This pest is a severe constraint to the production of cassava, food and income security for smallholder farmers. Crop resistance development through the selection of varieties with resistant traits against targeted pests is a promising approach to pest control. This study investigated cassava genotypes' response to natural infestation and determined their resistance levels against S. vayssierei. Six cassava genotypes (two local and four improved) were planted in a completely randomized block design with four replicates. Agronomic parameters and ARTS density were evaluated at 3, 6, 9 and 12 months after planting (MAP). Biochemical content was determined on the pith and cortex of 12 MAP aged tuberous roots. As a result, the improved Excel variety recorded the highest scale density per plant with 102.83 ± 4.14 ARTS/P at 9 MAP. At 12 MAP, high activity of total cyanide (69.18 ± 0.88 and 69.16 ± 1.44 mg/kg) and phenylalanine ammonia-lyase (0.142 ± 0.020 and 0.145 ± 0.010 ΔA/min/mg) were observed in the cortex of the tuberous roots of the improved varieties TMS 96/0023 and TMS 92/0057 which were colonized by the lowest ARTS density. The local variety (Douma) had a high content of total phenols (44.87 ± 1.15 µg/g) in the pith. It also produced the highest yield (23.8 ± 2.9 t ha-1). Varieties TMS 96/0023, TMS 92/0057 and Douma may be the most suitable varieties for the control of ARTS stress.

Spraying chitosan on cassava roots reduces postharvest deterioration by promoting wound healing and inducing disease resistance

Postharvest damage makes cassava roots vulnerable to pathogen infections and decay, which significantly hinders the development of the cassava industry. The objective of this study was to assess the antibacterial properties of chitosan in vitro, as well as its effect on wound healing and resistance in cassava roots. The findings demonstrated that the bacteriostatic effect of chitosan became increasingly prominent as the concentration of chitosan enhanced. Chitosan at a concentration of 0.5 mg/mL was revealed to significantly inhibit the germination of P. palmivora spores and damage to their structure. Moreover, chitosan activated the transcription of crucial genes and enzyme activities associated with the phenylpropane metabolism pathway in cassava roots, thus promoting rapid lignin accumulation and resulting in the early formation of a fracture layer. Chitosan was also found to enhance cassava root resistance by promoting the expression of pathogenesis-related proteins and the accumulation of flavonoids and total phenols. After 48 h of inoculation, cassava roots treated with chitosan exhibited a 51.4 % and 53.4 % decrease in lesion area for SC9 and SC6 varieties, respectively. The findings of this study offer a novel approach for managing postharvest deterioration of cassava roots.

To what extent are orally ingested nanoplastics toxic to the hippocampus in young adult rats?

As the use of plastic-containing materials in our daily lives becomes increasingly common, exposure to nanoplastics accordingly becomes inevitable. Micro and nanoplastics released from large amounts of plastic waste constitute a serious environmental problem. Therefore, this study aimed to examine the effects of polystyrene nanoplastic (PS-NP) on the hippocampus. MATERIAL AND METHOD: Thirty Wistar albino rats, 15 male and 15 female, aged 6-8 weeks, were used in the research. These were randomly divided into three groups of five males and five females each. A five-minute open field test was applied to all rats on the first and last days of the study. Three groups of rats (Control, NP1 and NP2) received the standard chow and water. Additionally, rats in the first neoplastic group (NP1) received 25 mg/kg PS-NP and rats in the second nanoplastic group (NP2) received 50 mg/kg PS-NP, at the same time each day by oral gavage. The rats were sacrificed under deep anesthesia at the end of four weeks. The hippocampi were removed and subjected to histopathological and biochemical analyses. RESULTS: Green fluorescent dots were detected in the hippocampi of both dose groups receiving nanoplastics (NPs) administered orally to female and male rats. Histopathological examination revealed neuronal degeneration in the hippocampi of male and female rats from both dose groups. However, while no significant difference was observed among the groups in terms of changes in antioxidant enzyme values and open-field test data in male rats, significant differences in peroxidase (POD) and glutathione S-transferase (GST) values and fecal boli and grooming numbers were determined in female rats exposed to NPs. In conclusion, exposure to NP substances extend as far as the hippocampus, causing neuronal damage and behavioral problems.

Reactive oxygen species turnover, phenolics metabolism, and some key gene expressions modulate postharvest physiological deterioration in cassava tubers

Rapid postharvest physiological deterioration (PPD) in cassava (Manihot esculenta Crantz) tuber is a significant concern during storage. The freshly harvested tubers start spoiling within 24 to 72 h. Accumulation of H2O2 is one of the earliest biochemical events that occurred during PPD, which was detected using the 3,3 diaminobenzidine (DAB) in two contrast cassava genotypes, MNP Local A (29-57 μg g-1) and Sree Prakash (64-141 μg g-1). Accumulating the fluorescence hydroxycoumarin compounds emitted by the cassava tubers observed under an ultraviolet (UV) lamp showed significant variations at 0, 3, 6, 9, 12, and 15 days of storage. The total phenolics and carotenoids significantly and negatively correlated with PPD progression; however, the anthocyanin and flavonoids positively correlated with the PPD-anchored ROS accumulation. The primary compound, Phthalic acid, di(2-propylpentyl) ester, was identified in both the cassava tubers, Sree Prakash (57.21 and 35.21%), and MNP Local A (75.58 and 60.21%) at 0, and 72 h of PPD, respectively. The expression of PPD-associated genes APX-2, APX-3, PAL, and AP was higher at 6-12 days of PPD, which signified the synthesis of ROS turnover and phenylpropanoid biosynthesis. A significant, strong, and positive correlation was established between the secondary metabolites and PPD signaling gene expression, which was inversely correlated with hydroxycoumarin and H2O2 accumulation. MNP Local A tubers exhibited longer storage life of 15 days with a low PPD score, higher metabolites synthesis, and gene expression. The PPD-resistant lines may be used to augment cassava breeding strategies for large-scale commercial and industrial use.

Dehydroascorbate induces plant resistance in rice against root-knot nematode Meloidogyne graminicola

Ascorbic acid (AsA) is an important antioxidant in plants and regulates various physiological processes. In this study, we show that exogenous treatments with the oxidized form of AsA, that is, dehydroascorbate (DHA), activates induced systemic resistance in rice against the root-knot nematode Meloidogyne graminicola, and investigate the molecular and biochemical mechanisms underlying this phenotype. Detailed transcriptome analysis on roots of rice plants showed an early and robust transcriptional response on foliar DHA treatment, with induction of several genes related to plant stress responses, immunity, antioxidant activity, and secondary metabolism already at 1 day after treatment. Quantitative and qualitative evaluation of H₂ O₂ levels confirmed the appearance of a reactive oxygen species (ROS) burst on DHA treatment, both at the site of treatment and systemically. Experiments using chemical ROS inhibitors or scavengers confirmed that H₂ O₂ accumulation contributes to DHA-based induced resistance. Furthermore, hormone measurements in DHA-treated plants showed a significant systemic accumulation of the defence hormone salicylic acid (SA). The role of the SA pathway in DHA-based induced resistance was confirmed by nematode infection experiments using an SA-signalling deficient WRKY45-RNAi line and reverse transcription-quantitative PCR on SA marker genes. Our results collectively reveal that DHA activates induced systemic resistance in rice against the root-knot nematode M. graminicola, mediated through the production of ROS and activation of the SA pathway.

Nutrient Concentrations Induced Abiotic Stresses to Sweet Pepper Seedlings in Hydroponic Culture

The primary goal of this experiment was to investigate the effects of nutrient electrical conductivity (EC) on the growth and physiological responses of sweet pepper (Capsicum annuum L.) in hydroponic culture in a greenhouse. The plant growth parameters, leaf photosynthesis, root activity, soluble protein, malondialdehyde (MDA), proline, activities of antioxidant enzymes (AE), and the contents of plant mineral elements (PME) were measured in six different EC treatments. The results showed that very high or low EC treatments clearly decreased the plant height, stem diameter, shoot dry weight, and leaf net photosynthetic rate, while increasing the content of MDA and the activities of ascorbate peroxidase and guaiacol peroxidase. The contents of proline and soluble protein increased gradually from the low to high EC treatments. The root activities decreased significantly, and the main PME clearly did not increase or even decreased at high EC levels. Very high EC treatments suppressed growth even more than those of very low EC. Treatments that were too low or high EC suppressed plant growth, owing to abiotic stress (either nutrient deficiency or salinity), since the plants had to regulate the activities of AE and increase the accumulation of osmolytes to adjust to the abiotic stresses.

Assessment of the Impact of the Application of a Quercetin-Copper Complex on the Course of Physiological and Biochemical Processes in Wheat Plants (Triticum aestivum L.) Growing under Saline Conditions

Salt stress is one of the main stressors limiting plant growth and yield. As a result of salt stress, unfavorable changes in the photosynthesis process take place, leading to a decrease in plant productivity. Therefore, it is necessary to use biologically active substances that reduce the effects of this stress. An example of such a substance is quercetin, classified as a flavonoid, which plays an important role in alleviating the effects of salt stress, mainly by the inactivation of reactive oxygen species (ROS) and by improvement of the photosynthesis process. A study was made of the effect of the quercetin–copper complex (Q-Cu (II)), which has a stronger antioxidant effect than pure quercetin. By means of a pot experiment, the influence of solutions of the Q-Cu (II) complex (100 mg∙L⁻¹ [Q1], 500 mg∙L⁻¹ [Q2] and 1000 mg∙L⁻¹ [Q3]) on the physiological and biochemical processes occurring in wheat plants subjected to salt stress was investigated. The plants were given two sprays of Q-Cu (II) solution, and their physiological parameters were examined both 1 and 7 days after each application of this solution. The level of ROS and the activity of antioxidant enzymes (catalase [CAT], superoxide dismutase [SOD] and guaiacol peroxidase [GPOX]) were also determined. It has been shown that spraying with Q2 and Q3 solutions improves the chlorophyll content, the values of chlorophyll fluorescence parameters (the photochemical efficiency of PS II [F_v/F_m], the maximum quantum yield of primary photochemistry [F_v/F₀], and the performance index of PS II [PI]), and gas exchange (net photosynthetic rate [P_n], stomatal conductance [g_s], transpiration rate [E] and intercellular CO₂ concentration [C_i]). As a result of the application of Q2 and Q3 solutions, the level of ROS and the activity of the antioxidant enzymes tested decreased, which means that these concentrations are most effective in counteracting the effects of salt stress.

Integrative Transcriptome and Proteome Analysis Reveals the Absorption and Metabolism of Selenium in Tea Plants [Camellia sinensis (L.) O. Kuntze]

Certain tea plants (Camellia sinensis) have the ability to accumulate selenium. In plants, the predominant forms of bioavailable Se are selenite (SeO3 2-) and selenate (SeO4 2-). We applied transcriptomics and proteomics to hydroponically grown plants treated with selenite or selenate for 48 h in the attempt to elucidate the selenium absorption and assimilation mechanisms in tea. A total of 1,844 differentially expressed genes (DEGs) and 691 differentially expressed proteins (DEPs) were obtained by comparing the Na2SeO3 and Na2SeO4 treatments against the control. A GO analysis showed that the genes related to amino acid and protein metabolism and redox reaction were strongly upregulated in the plants under the Na2SeO3 treatment. A KEGG pathway analysis revealed that numerous genes involved in amino acid and glutathione metabolism were upregulated, genes and proteins associated with glutathione metabolism and ubiquinone and terpenoid-quinone biosynthesis were highly expressed. Genes participating in DNA and RNA metabolism were identified and proteins related to glutathione metabolism were detected in tea plants supplemented with Na2SeO4. ABC, nitrate and sugar transporter genes were differentially expressed in response to selenite and selenate. Phosphate transporter (PHT3;1a, PHT1;3b, and PHT1;8) and aquaporin (NIP2;1) genes were upregulated in the presence of selenite. Sulfate transporter (SULTR1;1 and SULTR2;1) expression increased in response to selenate exposure. The results of the present study have clarified Se absorption and metabolism in tea plants, and play an important theoretical reference significance for the breeding and cultivation of selenium-enriched tea varieties.

Effects of vacuum packaging storage of minimally processed cassava roots at various temperatures on microflora, tissue structure, starch extraction by wet milling and granule quality

BACKGROUND

Vacuum package storage is commonly applied to reduce postharvest deterioration in minimally processed cassava roots. However, the influence of vacuum packaging conditions on root end-use quality is poorly understood. Hence, the effects of vacuum packaged storage at ambient, refrigerated and freezing temperatures on microflora, cassava tissue structure and starch extraction by wet milling were studied.

RESULTS

Vacuum packaged storage temperature strongly affected cassava root quality. Minimal adverse effects were obtained with frozen storage. With refrigerated storage, there was negligible microbial growth but some disruption of the parenchyma cell wall structure suggestive of chilling injury. With ambient temperature storage, there was considerable Lactobacilli dominated fermentation. This caused substantial cell degradation, probably due to the production of extracellular cellulolytic and other cell wall degrading enzymes. A benefit of this cell wall breakdown was that it substantially improved starch extraction with wet milling from the stored cassava pieces; by 18% with pieces that had been ambient vacuum packaged and wet milled using a 2000 μm opening screen. However, ambient temperature storage resulted in some starch granule pitting due to the action of extracellular amylases from the fermenting microorganisms.

CONCLUSION

The best vacuum packaging storage conditions for minimally processed cassava depends on application and cost. For short-term storage, refrigeration would be best for vegetable-type products. For several months storage, freezing is best. For wet milling applications, this could be combined with subsequent short-term ambient temperature storage as it improves starch extraction efficiency and could reduce distribution energy costs. © 2021 Society of Chemical Industry.

Extraction kinetics, physicochemical properties and immunomodulatory activity of the novel continuous phase transition extraction of polysaccharides from Ganoderma lucidum

Ganoderma lucidum polysaccharides (GLP) possess remarkable bioactivity and have been studied widely. However, the application of new technologies in the polysaccharide extraction has not been investigated. Herein, a novel continuous phase transition extraction (CPTE) technology was applied for the extraction of polysaccharides from Ganoderma lucidum. The extraction kinetics, physicochemical properties and immunomodulatory activity of GLP were evaluated. The kinetics results showed that the extraction process could be fitted to a two-site kinetic model due to the high R² values in the range of 0.9939-0.9999. Polysaccharides extracted by different technologies showed that GLP yield by CPTE could be significantly improved, which was 3.34 times and 2.68 times that of hot water and ultrasonic-assisted extraction, respectively. Molecular weight distribution analysis indicated that high molecular mass polysaccharide proportion by CPTE was the highest among the three extraction methods, which was 2.03 times and 3.41 times as much as that of the hot water and ultrasonic-assisted extraction. Morphology analysis showed that CPTE treatment caused disruption of most of the cells and effective release of intracellular components, implying that CPTE was beneficial to extract polysaccharides. Furthermore, the immunomodulatory assays demonstrated that GLP significantly enhanced the proliferation and production of NO, TNF-α and IL-6 in macrophages. Therefore, CPTE was more effective for extracting polysaccharides from Ganoderma lucidum than the common extraction.

Tracking the time-dependent and tissue-specific processes of arsenic accumulation and stress responses in rice (Oryza sativa L.)

The present study analysed time (0.5 h to 24 h) and tissue [roots, old leaves (OL) and young leaves (YL)] dependent nature of arsenic (As) accumulation and ensuing responses in two contrasting varieties of rice (Oryza sativa L.); Pooja (tolerant) and CO-50 (moderately sensitive). Arsenic accumulation was 5.4-, 4.7- and 7.3-fold higher at 24 h in roots, OL and YL, respectively of var. CO-50 than that in var. Pooja. Arsenic accumulation in YL depicted a delayed accumulation; at 2 h onwards in var. Pooja (0.23 µg g^-1 dw) while at 1 h onwards in var. CO50 (0.26 µg g^-1 dw). The responses of oxidative stress parameters, antioxidant enzymes, metabolites and ions were also found to be tissue- and time-dependent and depicted differential pattern in the two varieties. Among hormone, salicylic acid and abscisic acid showed variable response in var. Pooja and var. CO-50. Metabolite analysis depicted an involvement of various metabolites in As stress responses of two varieties. In conclusion, an early sensing of the As stress, proper coordination of hormones, biochemical responses, ionic and metabolic profiles allowed var. Pooja to resist As stress and reduce As accumulation more effectively as compared to that of var. CO-50.

Effect of soil amendments on antioxidant activity and photosynthetic pigments in pea crops grown in arsenic contaminated soil

The mechanism of arsenic (As) immobilization in soils is crucial for improving photosynthetic pigments and antioxidants in food crops. The effects of soil amendments with arbuscular mycorrhizal fungi (AMF), biochar (BC), selenium (Se), sulfur (S) and Si-gel on the concentrations of chlorophyll, carotenoid, proline, malondialdehyde (MDA), and the activity of ascorbate peroxidase (APX), guaiacol peroxidase (POD), and catalase (CAT) were studied in BARI pea (Pisum sativum) under As stress. Soil amendments with AMF, Se, Si-gel and S enhanced chlorophyll a and total chlorophyll contents by 31–35% and 60–75%, respectively. Likewise, CAT activity was increased by 24–46% in BC, AMF, Se, Si-gel and S-treated pea, respectively. APX and POD activity was also found to be enriched with the treatment of BC, AMF and Se. In contrast, the content of MDA and proline was found lower than that of control in peas. These findings indicate that oxidative damage, osmotic stress and cell injury were possibly reduced in As-stressed peas. Particularly, AMF and Se both were comparatively more potential in comparison to BC. Thus, soil amendments with AMF, BC and Se are significantly important for improving antioxidant enzyme activity of food crops grown in soil with elevated As levels.

Freezing Tolerance of Lolium multiflorum/Festuca arundinacea Introgression Forms is Associated with the High Activity of Antioxidant System and Adjustment of Photosynthetic Activity under Cold Acclimation

Though winter-hardiness is a complex trait, freezing tolerance was proved to be its main component. Species from temperate regions acquire tolerance to freezing in a process of cold acclimation, which is associated with the exposure of plants to low but non-freezing temperatures. However, mechanisms of cold acclimation in Lolium-Festuca grasses, important for forage production in Europe, have not been fully recognized. Thus, two L. multiflorum/F. arundinacea introgression forms with distinct freezing tolerance were used herein as models in the comprehensive research to dissect these mechanisms in that group of plants. The work was focused on: (i) analysis of cellular membranes' integrity; (ii) analysis of plant photosynthetic capacity (chlorophyll fluorescence; gas exchange; gene expression, protein accumulation, and activity of selected enzymes of the Calvin cycle); (iii) analysis of plant antioxidant capacity (reactive oxygen species generation; gene expression, protein accumulation, and activity of selected enzymes); and (iv) analysis of Cor14b accumulation, under cold acclimation. The more freezing tolerant introgression form revealed a higher integrity of membranes, an ability to cold acclimate its photosynthetic apparatus and higher water use efficiency after three weeks of cold acclimation, as well as a higher capacity of the antioxidant system and a lower content of reactive oxygen species in low temperature.

Comparative ecotoxicity of single and binary mixtures exposures of cadmium and zinc on growth and biomarkers of Lemna gibba

In the present study, single and mixture effects of cadmium (Cd) and zinc (Zn) on Lemna gibba were analyzed and compared using growth parameters, based on frond number and fresh weight, and biochemical parameters, such as pigment, protein content and activity of antioxidant enzymes. Plants were exposed for 7 days to these metals in nutrient solution. Single and mixture exposures affected plant growth and the biomarkers of the antioxidant response. Considering the growth parameters, Cd was found to be much more toxic than Zn. IC50-7d, based on growth rate calculated on frond number, were 17.8 and 76.73 mg/L, and on fresh weight were 1.08 and 76.93 mg/L, for Cd and Zn respectively. For Cd, LOEC values were obtained at 2.06 and 1.03 mg/L, for frond number and fresh weight respectively; while for Zn, at 20.1 and 74.6 mg/L. A high toxicity effect, considering the same response variables, was observed in plants exposed to the mixtures. Three fixed ratios, based on toxic units (TU) were assayed, ratio 1: 2/3 Cd-1/3 Zn, ratio 2: 1/2 Cd-1/2 Zn and ratio 3: 1/3 Cd-2/3 Zn. Ratio 3 (where Zn was added in higher proportion) was the less toxic. All concentrations of Ratio 1 and 2 significantly inhibited plant growth, showing a 100% inhibition of growth rate at the highest concentrations when based on frond number. Catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APOX; EC 1.11.1.11) and guaiacol peroxidase (GPOX; EC 1.11.1.7) activities in single metals assays were higher than controls. In mixture tests, the activity of APOX and GPOX was significantly stimulated in plants exposed to all evaluated combinations, while CAT was mainly stimulated in Ratio 3. It was observed that the activity of the enzymes was increased in the mixtures compared with similar concentrations evaluated individually. APOX activity was observed to fit the CA model and following a concentration-response pattern. The response of this antioxidant enzyme could serve as a sensitive stressor biomarker for Cd-Zn interactions. Frond number in Cd-Zn mixtures was not well predicted from dissolved metal concentration in solution using concentration addition (CA) as reference model, as results showed that toxicity was more than additive, with an average of ΣTU = 0.75. This synergistic effect was observed up to 50 mg Zn/L in the mixture, but when it was present in higher concentrations a less than additive effect was observed, indicating a protective effect of Zn. A synergistic and dose-ratio deviations from CA model were also observed.

The ascorbate peroxidase 1 regulates ascorbic acid metabolism in fresh-cut leaves of tea plant during postharvest storage under light/dark conditions

Postharvest storage conditions affect the ascorbic acid (AsA) levels in fresh-cut leaves of horticultural crops. However, the detailed mechanism of AsA metabolism in the fresh-cut leaves of tea plant (Camellia sinensis) during postharvest storage under light/dark conditions remains unclear. To investigate the AsA mechanism, we treated fresh-cut tea leaves with light/dark during postharvest storage. An ascorbate peroxidase 1 (CsAPX1) protein involved in AsA metabolism was identified by iTRAQ analysis. Gene expression profile of CsAPX1 encoding ascorbate peroxidase (APX) was regulated by light/dark conditions. AsA accumulation and APX activity were suppressed by light/dark conditions. SDS-PAGE analysis showed that the molecular mass of recombinant CsAPX1 protein was about 34.45 kDa. Subcellular localization indicated that CsAPX1 protein was a cytosol ascorbate peroxidase. Overexpression CsAPX1 in Arabidopsis indicated that the decrease of AsA content and APX activity in transgenic lines were less significant than that of WT during postharvest storage under light/dark conditions. These data suggested that CsAPX1 involved in regulating AsA metabolism through effecting on the changes of AsA accumulation and APX activity in fresh-cut tea leaves during postharvest storage under light/dark conditions.

Assessment of changes in growth traits, oxidative stress parameters, and enzymatic and non-enzymatic antioxidant defense mechanisms in Lepidium draba plant under osmotic stress induced by polyethylene glycol

Lepidium draba is a weed with the medicinal properties which few researches have been done on it. In this study, some traits, related to the osmotic stress, in 14-day-old L. draba sprouts that were grown 9 days in the presence of various doses of polyethylene glycol 6000 (PEG 6000) including 0, 3, 6, 9, and 12%, with different osmotic potentials (- 0.04, - 0.12, - 0.23, - 0.34, and - 0.48 MPa, respectively) were investigated. Based on our results, germination percentage besides stem and root lengths decreased with increasing the concentrations of PEG. The contents of electrolyte leakage, malondialdehyde, other aldehydes, total protein, free amino acids, total soluble carbohydrate as well as free proline increased with increasing the concentrations of PEG. Also, for the first time, our results have proven that under osmotic stress, there is an adverse relationship between hydrogen peroxide content and the activity of catalase, peroxidase, ascorbate peroxidase, and guaiacol peroxidase enzymes, such that hydrogen peroxide content decreased with induction of PEG up to 6% and after that increased, while the activity of catalase, peroxidase, ascorbate peroxidase, and guaiacol peroxidase enzymes increased up to 6% PEG and after that decreased. The expression levels of catalase, peroxidase, ascorbate peroxidase, and guaiacol peroxidase genes showed the same pattern as was seen for these enzyme activities. According to the results of this study, it can be deduced that decreasing H₂O₂ content cannot be the main reason for other oxidative stress parameters to decrease. In this study, P5CS and P5CR gene expression levels increased with increasing levels of PEG up to 12% which was completely similar to free proline content. Based on our results, L. draba can be considered as a semi-tolerant plant to osmotic stress.

Simultaneous quantification of peroxidase and ascorbic acid in biosamples with an automatic system based on a Fe(iii)/methylthymol blue-carbon dot simulative enzyme

Simultaneous and automatic quantification of peroxidase and ascorbic acid based on one reaction system and application of a carbon dot simulative enzyme.

Groundwater inhabited Bacillus and Paenibacillus strains alleviate arsenic-induced phytotoxicity of rice plant

Arsenic contamination in agricultural soil now imposing a major threat to crop productivity and causing several hazardous health effects through percolation in food chain. Bioremediation, an efficient way of soil health restoration toward sustainability offered by some soil-borne microorganisms, has been reported. The present work deals with application of two potent arsenic-tolerant bacterial strains (Bacillus thuringiensis A01 and Paenibacillus glucanolyticus B05), obtained from natural sources in modulating overall growth and antioxidant defense against arsenic-treated rice plants. Between the two, former could reduce arsenic uptake up to 56% (roots) and 85% (shoots), and the preceding one up to 31% (roots) and 65% (shoots) in a hydroponic environment. Germination percentage was noted to be enhanced significantly (p ≤ 0.05). Expression of oxidative stress defensive enzymes such as superoxide dismutase, peroxidase and catalase have been augmented at seedling stages (21 days) toward detoxification of arsenic imposed excess ROS generation. Increment of leaf Thiobarbituric acid reactive substances due to arsenic exposure have been ameliorated by both the bacterial application. Phenolic and flavonoid mediated free radical scavenging ability of the test plants elevated significantly (p ≤ 0.05). The present work revealed that, selected bacterial strains can perform efficient bioremediation against arsenic pollutant rice cultivation.

Analysis of wheat gene expression related to the oxidative stress response and signal transduction under short-term osmotic stress

Water shortage is a major environmental stress that causes the generation of reactive oxygen species (ROS). The increase in ROS production induces molecular responses, which are key factors in determining the level of plant tolerance to stresses, including drought. The aim of this study was to determine the expression levels of genes encoding MAPKs (MAPK3 and MAPK6), antioxidant enzymes (CAT, APX and GPX) and enzymes involved in proline biosynthesis (P5CS and P5CR) in Triticum aestivum L. seedlings in response to short-term drought conditions. A series of wheat intervarietal substitution lines (ISCSLs) obtained by the substitution of single chromosomes from a drought-sensitive cultivar into the genetic background of a drought-tolerant cultivar was used. This source material allowed the chromosomal localization of the genetic elements involved in the response to the analyzed stress factor (drought). The results indicated that the initial plant response to drought stress resulted notably in changes in the expression of MAPK6 and CAT and both the P5CS and P5CR genes. Our results showed that the substitution of chromosomes 3B, 5A, 7B and 7D had the greatest impact on the expression level of all tested genes, which indicates that they contain genetic elements that have a significant function in controlling tolerance to water deficits in the wheat genome.

Reliable method for the detection of horseradish peroxidase activity and enzyme kinetics

Enzyme-catalyzed reactions are complicated and their kinetics depend on various chemical and physical factors. In a simple enzyme-catalyzed reaction, the enzyme kinetics often involve two or more substrates. However, this complexity is often ignored when studying enzyme kinetics or determining enzyme activity. Such an example is horseradish peroxidase (HRP), whose activity and kinetics in the reduction of H₂O₂ are usually detected and studied using spectroanalysis, with guaiacol (GA) as the hydrogen donor. In this process, the concentrations of two substrates, GA and H₂O₂, both change, which makes the practical detection, based on determination of the GA oxydate, GA(O), totally wrong. In this study, we introduce a new electrochemical method for detecting the specific activity (SA) and studying the enzyme kinetics of HRP. This electrochemical method was used to directly detect one substrate (H₂O₂) while the concentration of the other substrate (GA) was kept constant by adding ascorbic acid to the system to reduce GA(O) and regenerate GA. For the first time, this HRP-catalyzed reaction, including the mechanism and kinetics, was investigated precisely using a simple electrochemical method. The maximum SA and reaction rate constant k₁ were reliably detected and calculated. The proposed method indicated that the SA of commercially available HRP (300 U mg^-1 detected by spectroanalysis) was 1228.8 U mg^-1 at a GA concentration of 4.5 mM, and up to 2049.9 U mg^-1 as the GA concentration tended toward infinity. Our results suggest that reported methods for detecting enzyme activity and/or kinetics should be re-examined according to the catalytic mechanism of the enzyme.

Proteomic analysis of injured storage roots in cassava (Manihot esculenta Crantz) under postharvest physiological deterioration

Postharvest physiological deterioration (PPD) is a global challenge in the improvement of cassava value chain. However, how to reduce cassava spoilage and reveal the mechanism of injured cassava storage roots in response to PPD were poorly understood. In the present study, we investigated the activities of antioxidant enzymes of cassava injured storage roots in PPD-susceptible (SC9) and PPD-tolerant (QZ1) genotypes at the time-points from 0h to 120h, and further analyzed their proteomic changes using two-dimensional electrophoresis (2-DE) in combination with MALDI-TOF-MS/MS. Ninety-nine differentially expressed proteins were identified from SC9 and QZ1 genotypes in the pairwise comparison of 24h/0h, 48h/0h, 72h/0h and 96h/0h. Of those proteins were associated with 13 biological functions, in which carbohydrate and energy metabolism related proteins were the biggest amount differential proteins in both genotypes, followed by chaperones, DNA and RNA metabolism, and defense system. We speculated that SOD in combination with CAT activities would be the first line of defense against PPD to support PPD-tolerant cassava varieties. The four hub proteins including CPN60B, LOS2, HSC70-1 and CPN20B, produced from the network of protein-protein interaction, will be the candidate key proteins linked with PPD. This study provides a new clue to improve cassava PPD-tolerant varieties and would be helpful to much better understand the molecular mechanism of PPD of cassava injured storage roots.

Ozone-induced changes in the content of bioactive compounds and enzyme activity during storage of pepper fruits

This paper presents for the first time the results of investigations concerning the effect of treatment of whole pepper fruits with gaseous ozone and the refrigeration storage period conditions on pepper quality. The effects are reflected in changes in the flavonoid contents, the antioxidant activity of the phenolic compound fraction and the enzymes involved in phenylpropanoid metabolism. The investigations were carried out on a hot pepper fruit cultivar, Cyklon. It was found that the levels of a majority of flavonoids, in particular those of quercetin 3-O-rhamnoside and quercetin 3-O-rhamnoside-7-O-glucoside increased in the pericarp of fruits treated with ozone for 3h and stored for 20days (by 25% relative to the control). Simultaneously, reduced phenylalanine ammonia-lyase and tyrosine ammonia-lyase activity were noted, which implies slight degradation of enzymes caused by the ozone treatment and enhancement of the polyphenol oxidase and guaiacol oxidase activity involved in response to increased oxidative stress.

Data supporting the role of enzymes and polysaccharides during cassava postharvest physiological deterioration

This data article is referred to the research article entitled The role of ascorbate peroxidase, guaiacol peroxidase, and polysaccharides in cassava (Manihot esculenta Crantz) roots under postharvest physiological deterioration by Uarrota et al. (2015). Food Chemistry 197, Part A, 737–746.

The stress duo to PPD of cassava roots leads to the formation of ROS which are extremely harmful and accelerates cassava spoiling. To prevent or alleviate injuries from ROS, plants have evolved antioxidant systems that include non-enzymatic and enzymatic defence systems such as ascorbate peroxidase, guaiacol peroxidase and polysaccharides. In this data article can be found a dataset called “newdata”, in RData format, with 60 observations and 06 variables. The first 02 variables (Samples and Cultivars) and the last 04, spectrophotometric data of ascorbate peroxidase, guaiacol peroxidase, tocopherol, total proteins and arcsined data of cassava PPD scoring. For further interpretation and analysis in R software, a report is also provided. Means of all variables and standard deviations are also provided in the Supplementary tables (“data.long3.RData, data.long4.RData and meansEnzymes.RData”), raw data of PPD scoring without transformation (PPDmeans.RData) and days of storage (days.RData) are also provided for data analysis reproducibility in R software.

Comparative Physiological and Transcriptomic Analyses Reveal the Actions of Melatonin in the Delay of Postharvest Physiological Deterioration of Cassava

Melatonin plays important roles in various aspects of biological processes. However, it is less known on the effects and mechanism of melatonin on the postharvest physiological deterioration (PPD) process of cassava, which largely restricts the potential of cassava as a food and industrial crop. In this study, we found that exogenous application of melatonin significantly delayed PPD of cassava tuberous roots by reducing H2O2 content and improving activities of catalase and peroxidase. Moreover, 3425 differentially expressed genes by melatonin during the PPD process were identified by transcriptomic analysis. Several pathways were markedly affected by melatonin treatments, including metabolic-, ion homeostasis-, and enzyme activity-related processes. Further detailed analysis revealed that melatonin acted through activation of ROS-scavenging and ROS signal transduction pathways, including antioxidant enzymes, calcium signaling, MAPK cascades, and transcription factors at early stages. Notably, the starch degradation pathway was also activated at early stages, whereas it was repressed by melatonin at middle and late stages, thereby indicating its regulatory role in starch metabolism during PPD. Taken together, this study yields new insights into the effect and underlying mechanism of melatonin on the delay of PPD and provides a good strategy for extending shelf life and improvement of cassava tuberous roots.