Abscisic Acid Increases Hydrogen Peroxide in Multiple Subcellular Compartments to Drive Stomatal Closure

Stomatal closure regulates transpiration and gas exchange in response to environmental cues. Drought upregulates ABA signaling, which elevates levels of reactive oxygen species (ROS). However, the subcellular location and identity of these ROS has received limited study. We found that in guard cells, ABA increased fluorescence of the general redox sensor, dichlorofluorescein (DCF), in distinct subcellular locations including chloroplasts, cytosol, nuclei, and cytosolic puncta. These changes were lost in ABA-insensitive quintuple receptor mutant and accentuated in an ABA-hypersensitive mutant. ABA induced ROS accumulation in these subcellular compartments was lost in mutants with defects in genes encoding hydrogen peroxide synthesizing respiratory burst oxidase homolog (RBOH) enzymes and guard cells treated with the RBOH inhibitor VAS2870, while exogenous hydrogen peroxide treatment is sufficient to close guard cells. The hydrogen peroxide-selective probe, peroxy orange1, also showed ABA-dependent increases in chloroplasts and cytosolic puncta. Using the more sensitive genetically-encoded hydrogen peroxide reporter roGFP-Orp1, we also detected significant hydrogen peroxide increases in the cytosol and nucleus. These cytosolic puncta accumulate ROS after ABA treatment show colocalization with Mitotracker and with a mitochondrial targeted mt-roGFP2-Orp1, which also revealed ABA-increased ROS in mitochondria. These results indicate that elevated hydrogen peroxide after ABA treatment in these subcellular compartments is necessary and sufficient to drive stomatal closure.

Differential Effect of Hydroxen Peroxide οn Toxic Cyanobacteria of Hypertrophic Mediterranean Waterbodies

Cyanobacterial blooms have been known since ancient times; however, they are currently increasing globally. Human and ecological health risks posed by harmful cyanobacterial blooms have been recorded around the world. These risks are mainly associated with their ability to affect the ecosystem chain by different mechanisms like the production of cyanotoxins, especially microcystins. Their expansion and their harmful effects have led many researchers to seek techniques and strategies to control them. Among them, hydrogen peroxide could be a promising tool against cyanobacteria and cyanotoxins and it is well-established as an environmentally friendly oxidizing agent because of its rapid decomposition into oxygen and water. The aim of the present study was to evaluate the effect of hydrogen peroxide on phytoplankton from two hypertrophic waterbodies in Greece. The effect of hydrogen peroxide on concentration of microcystins found in the waterbodies was also studied. Treatment with 4 mg/L hydrogen peroxide was applied to water samples originated from the waterbodies and Cyanobacterial composition and biomass, phycocyanin, chlorophyll-a, and intra-cellular and total microcystin concentrations were studied. Cyanobacterial biomass and phycocyanin was reduced significantly after the application of 4 mg/L hydrogen peroxide in water treatment experiments while chlorophytes and extra-cellular microcystin concentrations were increased. Raphidiopsis (Cylindrospermopsis) raciborskii was the most affected cyanobacterial species after treatment of the water of the Karla Reservoir in comparison to Aphanizomenon favaloroi, Planktolyngbya limnetica, and Chroococcus sp. Furthermore, Microcystis aeruginosa was more resistant to the treatment of Pamvotis lake water in comparison with Microcystis wesenbergii and Microcystis panniformis. Our study showed that hydrogen peroxide differentially impacts the members of the phytoplankton community, affecting, thus, its overall efficacy. Different effects of hydrogen peroxide treatment were observed among cyanobacerial genera as well as among cyanobacterial species of the same genus. Different effects could be the result of the different resistance mechanisms of each genus or species to hydrogen peroxide. Hydrogen peroxide could be used as a treatment for the mitigation of cyanobacterial blooms in a waterbody; however, the biotic and abiotic characteristics of the waterbody should be considered.

Upgrading the fermentability and prebiotic potential of palm decanter cake through fibre-degrading enzymatic treatments

Palm oil milling has produced tonnes of solid waste including palm decanter cake (PDC). The recalcitrant nature of PDC limits its full inclusion in animal feed. This study aims to investigate the effect of fibre-degrading enzyme such as cellulase and xylanase on the prebiotic activity and solid state fermentability of PDC. We used the following commercial enzyme loading: 5U cellulase (5UC), 5U xylanase (5UX) and combined enzymatic treatment 2.5U:2.5U (C25U) per gram of substrate to hydrolyse the defatted PDC. The sugar profile in the effluent was analysed by using high-performance liquid chromatography, and the degree of hydrolysis (DH) was estimated based on the total carbohydrates amount in the effluent. The DH of enzymatic-hydrolysed PDC followed the order of 5UC< C25U <5UX, which was 7.8 %, 44.2 2% and 46.27 %, respectively. The prebiotic activity score of ethanolic extract obtained from the PDC followed the order of untreated < C25U < 5UX < 5UC, which were -1.04, -0.74, -0.10 and 0.58, respectively. To further investigate the role of lignin (which can be eliminated through alkaline hydrogen peroxide treatment (AHPT) on the extent of hydrolysis and the fermentability of enzymatic-hydrolysed PDC, we tested the invasion capacity of fungus Aspergillus oryzae on untreated, and AHPT followed by enzymatic-treated PDC. Pre-treatment of PDC with AHP improved accessibility for enzymatic hydrolysis in which the highest fungus growth rate was observed on the AHP-C25U PDC. Enzymatic treatment succeeding AHPT is a feasible way to improve the fermentability of palm decanter cake.

Effect of hydrogen peroxide treatment on the concentration of volatile compound in coriander seeds oil

Coriander seeds essential oil have shown some remarkable biological properties and health benefits. The coriander seeds used in Indonesia are imported and also treated with hydrogen peroxide before reaching consumers. Hydrogen peroxide is known to be a strong oxidizer, but so far, there has been no information that explains its effects on the essential oil composition and concentration in coriander seed. This study aims to determine the effect of using hydrogen peroxide and the drying method on the composition of essential oils in coriander seeds. Yield and volatile oil compounds were measured, and the results were compared between the hydrogen peroxide concentration (0,35 and 50% ) and drying method (mechanical drying (50 ℃) and room temperature drying). GC-MS analysis detected linalool as the most common volatile constituent in all treatments. The highest concentration of linalool compounds (70.16%) was found in seeds without hydrogen peroxide (0%) treatment combined with mechanical drying, followed by without hydrogen peroxide (0% H2O2) combined with room drying (23.74%), then by 35% hydrogen peroxide combined with room drying (18.71%), 35% hydrogen peroxidecombined with mechanical drying (18.84%), 50% hydrogen peroxide combined with room drying (22.18%) and by 50% hydrogen peroxide combined with mechanical drying (15.45%). Therefore, the yield was clearly affected only by hydrogen peroxide treatment where no hydrogen peroxide treatment gave the highest yield. The drying method did not have any significant effect on yield.

Homogenization of Maritime Pine Wood Color by Alkaline Hydrogen Peroxide Treatment

The color of maritime pine wood is a critical parameter for manufacturing high added value materials (wood flooring or wood paneling for indoor applications). Actually, the color inhomogeneity between heartwood (Hw) and sapwood (Sw) can lead to a depreciation of the wood value and, therefore, to financial losses for wood products companies. In this article, the development of a color homogenization process based on alkaline hydrogen peroxide chemistry was studied. Maritime pine heartwood and sapwood powders were used to facilitate the chemical characterizations and colorimetric analyses by the CIEL*a*b* system. Brighter materials were obtained after the treatment by reducing significantly the color difference. The chemical modifications of wood surface were characterized by infrared spectroscopy analyses. The color evolution of the material overtime was also studied thanks to an accelerated ageing under UV irradiation. It was demonstrated that even if a color reversion occurred by oxidation, the color remained homogeneous between heartwood and sapwood.

P–111 Development of a flow cytometric assay for membrane lipid oxidation in human sperm

Study question Is a commercially available lipid peroxidation assay sensitive enough to detect sperm lipid membrane damage and thus provide a novel indicator of male fertility status? Summary answer Provisional results demonstrate the novelty of creating a protocol to identify and quantify sperm lipid membrane damage and indicate possible insight into individual male fertility. What is known already Cytotoxic lipid aldehydes such as 4-hydroxynonenal (4HNE) created by the damaging effects of reactive oxygen species (ROS) have been studied extensively in sperm, as an indicator of male fertility. This is due to their connection with detrimental effects on sperm function such as morphology, acrosome reactions, motility and fertilization of the oocyte. Although literature states the mechanisms of damage caused to the lipid membrane of the sperm cell, there is no evidence of its quantification or usage as a commercial fertility indicator for human males. Study design, size, duration Since the assay is still being developed, there is no formal study size or duration. The goal of this pilot study is to determine whether a commercial lipid peroxidation assay can detect the difference between sperm with high levels of oxidative damage and control sperm cells. We used the remains of sperm samples initially collected for standard semen analysis, which were flash-frozen and then assayed with / without hydrogen peroxide treatment to induce oxidative damage. Participants/materials, setting, methods Frozen sperm from consenting donors (n = 21) were washed, optionally treated with hydrogen peroxide to induce oxidative damage, stained with a commercially available lipid peroxidation sensor (LPS, Abcam ab243377), and the resulting fluorescence quantitated by flow cytometry. Assay optimization varied the numbers of sperm input to the protocol, the concentration of the peroxidation sensor, the amount and duration of hydrogen peroxide treatment and the effect of paraformaldehyde (PFA) fixation of samples before or after staining. Main results and the role of chance Successful detection of lipid damage in control samples We observed a significant difference at a p-value &lt; 0.05 between untreated samples and all positive controls with hydrogen peroxide concentrations stronger than 500uM (p &lt; 0.038) . This indicates that we can detect sperm bearing oxidative damage, and establishes the conditions required to make a positive control sample. Establishment of assay parameters Results indicate the concentration of sperm input to the protocol is not a significant factor for concentrations below 5 million/ml. Low concentration samples thus do not require further dilution before testing. Correlation with DNA damage A significant direct strong positive Pearson correlation coefficient (R = 0.93, p &lt; 0.023) was found between samples with low DNA fragmentation index (DFI (%), measured by flow cytometric staining with acridine orange) and the LPS flow cytometric data (%). Limitations, reasons for caution As yet our data only addresses high level lipid damage induced by peroxide treatment. It remains to be established whether it is possible to detect endogenous LPO damage due to oxidative stress in semen. Future work will correlate our data with motility information and oxidative stress data (measured by MiOXSYS). Wider implications of the findings: If we are able to develop a direct assay for sperm LPO, this will allow an additional avenue for testing patients with unexplained male infertility, which could in turn affect treatment choices and ART methodology. Improved diagnosis and treatment will potentially improve the lives of families with their fertility matters. Trial registration number Not applicable