Reactive Oxygen Species Scavenging Enzymes Research Articles

PSAG12-IPT overexpression in eggplant delays leaf senescence and induces abiotic stress tolerance

ABSTRACTThe isopentytransperase (IPT) gene, coupled to the SAG12 promoter, was successfully transferred into the eggplant (Solanum melongena L.) mediated by Agrobacterium tumefaciens. Four PSAG12 IPT overexpressing transgenic plants were identified by Southern blotting. Reverse transcription polymerase chain reaction revealed that IPT was expressed in senescent leaves under the control of SAG12 promoter. Compared with wild type eggplants, the leaf senescence was significantly delayed and tolerance to drought and cold stress was enhanced in the T1 generation of PSAG12-IPT transgenic eggplants. The contents of chlorophyll, indoleacetic acid, zeatin riboside, and gibberellic acid in the transgenic eggplants were higher than those in the wild type eggplants. The activities of reactive oxygen species-scavenging enzymes in the transgenic eggplants were also higher than those in the wild type eggplants. Abscisic acid and malondialdehyde levels were lower in the transgenic plants than in the wild type plants. Also the vegetative growth rate and yield of the transgenic plants were higher than those of the wild type eggplant. Our study suggests that the PSAG12-IPT expression cassette may be suitable for the genetic improvement of eggplant.

Transcriptome profiling reveals the genetic basis of alkalinity tolerance in wheat

BackgroundSoil alkalinity shows significant constraints to crop productivity; however, much less attention has been paid to analyze the effect of soil alkalinity on plant growth and development. Shanrong No. 4 (SR4) is an alkalinity tolerant bread wheat cultivar selected from an asymmetric somatic hybridization between the bread wheat cultivar Jinan 177 (JN177) and tall wheatgrass (Thinopyrum ponticum), which is a suitable material for studying alkalinity tolerant associate genes.ResultsThe growth of SR4 plant seedlings was less inhibited than that of JN177 when exposed to alkalinity stress conditions. The root cytosolic Na+/K+ ratio in alkalinity stressed SR4 was lower than in JN177, while alkalinity stressed SR4 contained higher level of nutrient elements than in JN177. SR4 plant seedlings accumulated less malondialdehyde (MDA) and reactive oxygen species (ROS), it also showed higher activity of ROS scavenging enzymes than JN177 under alkalinity stress. The root intracellular pH decreased in both alkalinity stressed JN177 and SR4, however, it was much lower in SR4 than in JN177 under alkalinity stress. The transcriptomes of SR4 and JN177 seedlings exposed to alkalinity stress were analyzed by digital gene expression tag profiling method. Alkalinity stress conditions up- and down-regulated a large number of genes in the seedling roots that play the functions in the categories of transcription regulation, signal transduction and protein modification.ConclusionsSR4 expresses a superior tolerance to alkaline stress conditions which is due to its strong absorbing ability for nutrient ions, a strong regulating ability for intracellular and rhizosphere pH and a more active ROS scavenging ability.

Trypsin inhibitors demonstrate antioxidant activities, inhibit A549 cell proliferation, and increase activities of reactive oxygen species scavenging enzymes.

OBJECTIVES:Protease inhibitors are one of the most promising and investigated subjects for their role in pharmacognostical and pharmacological studies. This study aimed to investigate antineoplastic and antioxidant activity of trypsin inhibitors (TIs) isolated from three plant sources and their inhibitory role in the cell line.MATERIALS AND METHODOLOGY:TIs were obtained from different plant sources. Antineoplastic potential on adenocarcinoma human alveolar basal epithelial cell line (A549) and normal Human Embryonic Kidney (HEK) was determined using MTT assay. Activities of antioxidant enzyme, nitric oxide scavenger, superoxide dismutase, glutathione S-transferase, and glutathione peroxidase were assessed in cell lines incubated with and without TIs. The outcome was analyzed by spectrophotometer.RESULTS:TIs showed the higher cytotoxicity on A549 cells as compared to normal HEK cell line. TIs exhibited fair increase in antioxidant enzyme activity in A549 cells as compared to control. This might be one of the strategies of antineoplastic effect in cancer cells.CONCLUSIONS:This study has reported the antioxidant and antineoplastic properties of these TIs for the first time in A549 cells (to the best of our knowledge). The results show that TIs possess ability to prevent cancer and diseases caused due to oxidative stress. Therefore, we conclude that TIs can be used as supplements along with the conventional drugs for increased efficacy in the treatment of diseases such as cardiovascular disease, atherosclerosis, and cancer.

Physiological, anatomical and antioxidant responses to salinity in the Mediterranean pastoral grass plant Stipa lagascae

Soil and water salinity is a major environmental problem in the dry Mediterranean regions, affecting rangeland production. This study investigated the effects of salinity on the wild perennial grass (Poaceae) species Stipa lagascae R. & Sch., a potential forage plant that could be used to rehabilitate degraded rangelands in dry areas. In a laboratory, 3-month-old S. lagascae seedlings were subjected to increasing salt treatments (0–400 mm NaCl) for 45 days. Physiological and biochemical parameters such as leaf water potential (Ψw), leaf relative water content (RWC), proline, total soluble sugars, Na+, K+ and Ca2+ contents, and catalase, ascorbate peroxidase and glutathione reductase activities were measured. Total soluble sugars and proline concentrations increased and Ψw and RWC decreased with increasing salt concentrations. Lower salt concentrations induced a non-significant degradation of chlorophyll pigments. Shoot Na+ content increased with a salinity level, whereas shoot K+ and Ca2+ concentrations decreased and the K+ : Na+ ratio was lower. The salinity threshold, above which S. lagascae showed signs of damage, occurred at 300 mm. Plants have evolved reactive oxygen species (ROS) scavenging enzymes including catalase, ascorbate peroxidase and glutathione reductase, which provide cells with an efficient mechanism to neutralise ROS. The tolerance strategies of S. lagascae to moderate salinity seem to include osmotic adjustment through total soluble sugars and proline accumulation, and highly inducible antioxidative defence. Further investigations are necessary to study the effect of salt stress on distribution of ions (Na+, K+, Ca2+, Mg2+, Cl–, NO3–, SO42–) and osmotic adjustment. Photosynthesis and water-use efficiency parameters could be also useful tools.

Physiological mechanism of programmed cell death aggravation and acceleration in wheat endosperm cells caused by waterlogging

Wheat (Triticum aestivum L.) is one of the world’s three major food crops, the previous studies have indicated that the development of wheat endosperm cells underwent a special programmed cell death (PCD) and it could be accelerated by waterlogging. Hua 8 wheat cultivar (waterlogging tolerant) and Hua 9 (waterlogging sensitive) were used to reveal the physiological mechanism in this study. The results showed that after 7 days waterlogging treatment (DWT), the malondialdehyde (MDA) and O2 − (superoxide anion-free radical) were increased in both endosperms, especially in Hua 9 endosperm. Content of hydrogen peroxide (H2O2) increased significantly in both endosperms at 12 days after flowering (DAF) and 15 DAF. Proline, soluble sugar, and protein contents in Hua 8 endosperm were increased, nevertheless, the soluble sugar and proline contents declined in Hua 9 endosperm. The activities of superoxide dismutase (SOD) were induced in both endosperms, especially in Hua 8, while showed different change trends in activities of peroxidase (POD) and catalase (CAT). The SOD isozyme spectrogram appeared a new band, and CAT added two bands in Hua 8 endosperm after 7 DWT. CAT isozyme activity was increased markedly, but SOD isozyme in Hua 9 endosperm showed no significant effect by waterlogging stress. Above all, the accumulation of MDA, O2 −, and H2O2 in wheat endosperm after waterlogging led to the aggravation of PCD progress. Compared to Hua 8, more reactive oxygen species (ROS) accumulated in Hua 9 endosperm after waterlogging, combined with the weak ROS scavenging enzyme activities, in addition to the low osmotic pressure accelerated the PCD progress.

Trichoderma harzianum containing 1-aminocyclopropane-1-carboxylate deaminase and chitinase improved growth and diminished adverse effect caused by Fusarium oxysporum in soybean

An isolate, named Trichoderma harzianum T-soybean, showed growth-promoting for soybean seedlings and induced resistance to Fusarium oxysporum under greenhouse. Compared to control soybean seedlings, fresh weight, dry weight, lateral root number, chlorophyll content, root activity and soluble protein of plants pretreated with T-soybean increased, but initial pod height reduced. Furthermore, we found that T-soybean inhibited the growth of F. oxysporum by parasitic function. In addition, plate test results showed that culture filtrates of T-soybean also inhibited significantly F. oxysporum growth. Meanwhile, T-soybean treatment obviously reduced disease severity and induced quickly the H2O2 and O2− burst as well as pathogenesis related protein gene (PR3) expression after F. oxysporum inoculation, and subsequently diminished the cell damage in soybean caused by the pathogen challenge. Reactive oxygen species (ROS) scavenging enzymes activity analysis showed that the activities of peroxidase (POD), polyphenol oxidase (PPO) and superoxide dismutase (SOD) increased significantly in T-soybean pretreated plants. These results suggested that T-soybean treatment induced resistance in soybean seedlings to F. oxysporum by companying the production of ROS and the increasing of ROS scavenging enzymes activity as well as PR3 expression.

Overexpression of a Barley Aquaporin Gene, HvPIP2;5 Confers Salt and Osmotic Stress Tolerance in Yeast and Plants.

We characterized an aquaporin gene HvPIP2;5 from Hordeum vulgare and investigated its physiological roles in heterologous expression systems, yeast and Arabidopsis, under high salt and high osmotic stress conditions. In yeast, the expression of HvPIP2;5 enhanced abiotic stress tolerance under high salt and high osmotic conditions. Arabidopsis plants overexpressing HvPIP2;5 also showed better stress tolerance in germination and root growth under high salt and high osmotic stresses than the wild type (WT). HvPIP2;5 overexpressing plants were able to survive and recover after a 3-week drought period unlike the control plants which wilted and died during stress treatment. Indeed, overexpression of HvPIP2;5 caused higher retention of chlorophylls and water under salt and osmotic stresses than did control. We also observed lower accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), an end-product of lipid peroxidation in HvPIP2;5 overexpressing plants than in WT. These results suggest that HvPIP2;5 overexpression brought about stress tolerance, at least in part, by reducing the secondary oxidative stress caused by salt and osmotic stresses. Consistent with these stress tolerant phenotypes, HvPIP2;5 overexpressing Arabidopsis lines showed higher expression and activities of ROS scavenging enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and ascorbate peroxidase (APX) under salt and osmotic stresses than did WT. In addition, the proline biosynthesis genes, Δ1-Pyrroline-5-Carboxylate Synthase 1 and 2 (P5CS1 and P5CS2) were up-regulated in HvPIP2;5 overexpressing plants under salt and osmotic stresses, which coincided with increased levels of the osmoprotectant proline. Together, these results suggested that HvPIP2;5 overexpression enhanced stress tolerance to high salt and high osmotic stresses by increasing activities and/or expression of ROS scavenging enzymes and osmoprotectant biosynthetic genes.

Intracellular ROS scavenging and antioxidant enzyme regulating capacities of corn gluten meal-derived antioxidant peptides in HepG2 cells

The objective of this study was to investigate the intracellular reactive oxygen species (ROS) scavenging activities and antioxidant enzyme regulating capacities of corn gluten peptide fractions (CPFs) in HepG2 cells. A cellular antioxidant activity (CAA) assay was used to assess their antioxidant activities and revealed that both CPF1 (molecular weight <1kDa) and CPF2 (molecular weight between 1 and 3kDa) exhibited high cellular antioxidant activities with EC50 values of 2.85±0.19mg/mL and 5.05±0.32mg/mL, respectively. Both CPFs also exhibited cytoprotective effects and intracellular ROS scavenging activities in HepG2 cells subjected to oxidative stress by oxidation with H2O2. In addition, at concentrations of 2.50mg/mL, the CPFs increased the activity levels of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), as well as the total glutathione (GSH) levels in oxidized HepG2 cells (from 86.54% to 114.14% (CPF1) or 109.72% (CPF2) for SOD activity; from 71.91% to 107.64% (CPF1) or 106.50% (CPF2) for CAT activity; from 70.52% to 103.01% (CPF1) or 104.10% (CPF2) for GR activity; and from 81.39% to 114.00% (CPF1) or 108.82% (CPF2) for total GSH levels). These results suggested that both CPF1 and CPF2 exhibited positive effects on the activities of the intracellular antioxidant enzymes SOD, CAT and GR, as well as on the total GSH levels in HepG2 cells under conditions of oxidative stress. Furthermore, size exclusion gel chromatography and MALDI-TOF/TOF mass spectrometry revealed that the molecular weights of the antioxidant peptides in CPF1 were between 500Da to 900Da, and a novel antioxidant peptide consisting of GLLLPH (Gly-Leu-Leu-Leu-Pro-His) was identified in CPF1.

Trichoderma harzianum T-22 Induces Systemic Resistance in Tomato Infected by Cucumber mosaic virus.

Understanding the induction of plant defenses against viruses using biocontrol agents is essential for developing new strategies against these pathogens, given the ineffectiveness of chemical treatments. The ability of Trichoderma harzianum, strain T-22 (T22) to control Cucumber mosaic virus (CMV) in Solanum lycopersicum var. cerasiforme plants and the changes in the physiology of tomato treated/infected with T22/CMV were examined. Plant growth-promoting effects, photosynthetic performance, reactive oxygen species scavenging enzymes, and phytohormones were investigated. T22 improved tomato growth in terms of plant height and improved photosynthesis, total chlorophyll content and plant gas exchange. In contrast, CMV induced a negative effect on dry matter accumulation and inhibited the photosynthetic capacity. The analysis of plant hormones demonstrated that treating with T22 before or simultaneously to CMV infection, led to a systemic resistance by jasmonic acid/ethylene and salicylic acid signaling pathways. Conversely, systemic resistance was abscissic acid-dependent when T22 treatment was administered after the CMV infection. In conclusion, the data reported here indicate that the T22-based strategy may be the most effective measure against CMV.

Overexpression of AtEDT1/HDG11 in Chinese Kale (Brassica oleracea var. alboglabra) Enhances Drought and Osmotic Stress Tolerance.

Plants are constantly challenged by environmental stresses, including drought and high salinity. Improvement of drought and osmotic stress tolerance without yield decrease has been a great challenge in crop improvement. The Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a protein of the class IV HD-Zip family, has been demonstrated to significantly improve drought tolerance in Arabidopsis, rice, and pepper. Here, we report that AtEDT1/HDG11 confers drought and osmotic stress tolerance in the Chinese kale. AtEDT1/HDG11-overexpression lines exhibit auxin-overproduction phenotypes, such as long hypocotyls, tall stems, more root hairs, and a larger root system architecture. Compared with the untransformed control, transgenic lines have significantly reduced stomatal density. In the leaves of transgenic Chinese kale plants, proline (Pro) content and reactive oxygen species-scavenging enzyme activity was significantly increased after drought and osmotic stress, particularly compared to wild kale. More importantly, AtEDT1/HDG11-overexpression leads to abscisic acid (ABA) hypersensitivity, resulting in ABA inhibitor germination and induced stomatal closure. Consistent with observed phenotypes, the expression levels of auxin, ABA, and stress-related genes were also altered under both normal and/or stress conditions. Further analysis showed that AtEDT1/HDG11, as a transcription factor, can target the auxin biosynthesis gene YUCC6 and ABA response genes ABI3 and ABI5. Collectively, our results provide a new insight into the role of AtEDT1/HDG11 in enhancing abiotic stress resistance through auxin- and ABA-mediated signaling response in Chinese kale.

Overexpression of a Chitinase Gene from Trichoderma asperellum Increases Disease Resistance in Transgenic Soybean.

In the present study, a chi gene from Trichoderma asperellum, designated Tachi, was cloned and functionally characterized in soybean. Firstly, the effects of sodium thiosulfate on soybean Agrobacterium-mediated genetic transformation with embryonic tip regeneration system were investigated. The transformation frequency was improved by adding sodium thiosulfate in co-culture medium for three soybean genotypes. Transgenic soybean plants with constitutive expression of Tachi showed increased resistance to Sclerotinia sclerotiorum compared to WT plants. Meanwhile, overexpression of Tachi in soybean exhibited increased reactive oxygen species (ROS) level as well as peroxidase (POD) and catalase (SOD) activities, decreased malondialdehyde (MDA) content, along with diminished electrolytic leakage rate after S. sclerotiorum inoculation. These results suggest that Tachi can improve disease resistance in plants by enhancing ROS accumulation and activities of ROS scavenging enzymes and then diminishing cell death. Therefore, Tachi represents a candidate gene with potential application for increasing disease resistance in plants.

Abundant protein phosphorylation potentially regulates Arabidopsis anther development.

As the male reproductive organ of flowering plants, the stamen consists of the anther and filament. Previous studies on stamen development mainly focused on single gene functions by genetic methods or gene expression changes using comparative transcriptomic approaches, especially in model plants such as Arabidopsis thaliana However, studies on Arabidopsis anther protein expression and post-translational modifications are still lacking. Here we report proteomic and phosphoproteomic studies on developing Arabidopsis anthers at stages 4-7 and 8-12. We identified 3908 high-confidence phosphorylation sites corresponding to 1637 phosphoproteins. Among the 1637 phosphoproteins, 493 were newly identified, with 952 phosphorylation sites. Phosphopeptide enrichment prior to LC-MS analysis facilitated the identification of low-abundance proteins and regulatory proteins, thereby increasing the coverage of proteomic analysis, and facilitated the analysis of more regulatory proteins. Thirty-nine serine and six threonine phosphorylation motifs were uncovered from the anther phosphoproteome and further analysis supports that phosphorylation of casein kinase II, mitogen-activated protein kinases, and 14-3-3 proteins is a key regulatory mechanism in anther development. Phosphorylated residues were preferentially located in variable protein regions among family members, but they were they were conserved across angiosperms in general. Moreover, phosphorylation might reduce activity of reactive oxygen species scavenging enzymes and hamper brassinosteroid signaling in early anther development. Most of the novel phosphoproteins showed tissue-specific expression in the anther according to previous microarray data. This study provides a community resource with information on the abundance and phosphorylation status of thousands of proteins in developing anthers, contributing to understanding post-translational regulatory mechanisms during anther development.

Comprehensive Analysis of the Membrane Phosphoproteome Regulated by Oligogalacturonides in Arabidopsis thaliana.

Early changes in the Arabidopsis thaliana membrane phosphoproteome in response to oligogalacturonides (OGs), a class of plant damage-associated molecular patterns (DAMPs), were analyzed by two complementary proteomic approaches. Differentially phosphorylated sites were determined through phosphopeptide enrichment followed by LC-MS/MS using label-free quantification; differentially phosphorylated proteins were identified by 2D-DIGE combined with phospho-specific fluorescent staining (phospho-DIGE). This large-scale phosphoproteome analysis of early OG-signaling enabled us to determine 100 regulated phosphosites using LC-MS/MS and 46 differential spots corresponding to 34 pdhosphoproteins using phospho-DIGE. Functional classification showed that the OG-responsive phosphoproteins include kinases, phosphatases and receptor-like kinases, heat shock proteins (HSPs), reactive oxygen species (ROS) scavenging enzymes, proteins related to cellular trafficking, transport, defense and signaling as well as novel candidates for a role in immunity, for which elicitor-induced phosphorylation changes have not been shown before. A comparison with previously identified elicitor-regulated phosphosites shows only a very limited overlap, uncovering the immune-related regulation of 70 phosphorylation sites and revealing novel potential players in the regulation of elicitor-dependent immunity.

Effects of nano-TiO2 -LDPE packaging on postharvest quality and antioxidant capacity of strawberry (Fragaria ananassa Duch.) stored at refrigeration temperature.

Nano-TiO2 -low-density polyethylene (NTLDPE) packaging was prepared, and the effects of NTLDPE packaging on quality and antioxidant capacity of strawberry fruits were investigated. With increased barrier properties, NTLDPE packaging quickly formed a relative lower O2 and higher CO2 air composition in comparison with LDPE. It was also more efficient in maintaining the overall quality of strawberry fruit, as reflected by lower decay rate and weight loss, as well as retarding the decrease in firmness and titratable acid. Meanwhile, reactive oxygen species (ROS) including superoxide anion and hydrogen peroxide in NTLDPE-packed fruits were 10.8% and 21.9% lower, respectively. Furthermore, the activities of antioxidant enzymes involved in ROS scavenging in NTLDPE-packed fruits were significantly higher at the later period of storage time. Anthocyanin accumulation was inhibited, whereas ascorbic acid and total phenolics contents were better retained and 1-diphenyl-2-picrylhydrazyl radical scavenging activity was 13.2% higher in NTLDPE-packed fruit by the end of storage. These data indicate that the beneficial effects of NTLDPE packaging on postharvest quality and antioxidant capacity of strawberry are probably associated with the promotion of ROS scavenging and related antioxidant enzyme activities, and NTLDPE packaging together with refrigeration storage is a promising method for strawberry fruit preservation. © 2016 Society of Chemical Industry.

Effect of Reducing Nitric Oxide in Rumex K-1 Leaves on the Photoprotection of Photosystem II Under High Temperature with Strong Light

The purpose of this study was to explore the effect of reducing nitric oxide (NO) in Rumex K-1 leaves on the photoprotection of photosystem II (PSII) under high temperature with strong light. Reducing the content of NO in Rumex K-1 leaves significantly aggravated the PSII photoinhibition and net degradation of D1 protein under high temperature with strong light, but not under high temperature in the darkness. The reduction of NO remarkably inhibited the electron transport of PSII in the leaves under high temperature and strong light, which resulted in an increase in excitation pressure and an over-accumulation of reactive oxygen species (ROS). The over-accumulation of ROS further damaged PSII. However, when the synthesis of D1 protein was inhibited, the D1 protein content and PSII activity were no longer influenced by reducing NO content in the leaves. The reduction of NO in leaves decreased the activities of ROS scavenger enzymes after treatment with high temperature and strong light for 2 h, which enhanced the over-accumulation of ROS to damage photosynthetic apparatus severely. All of these results suggest that NO was involved in the synthesis of D1 protein. Maintaining physiologically appropriate NO content in leaves will alleviate net degradation of D1 protein under high temperature with strong light to keep photosynthetic electrons flowing smoothly, which mitigates the accumulation of ROS in photosystems to avoid damage to the photosynthetic apparatus. Therefore, NO plays an important role in maintaining higher PSII photosynthetic performance under high temperature with strong light.

Effect of Acetone on Reactive Oxygen Species to Mice Skin

Acetone is one of the organic solvents that causes skin barrier disruption such as eczema and dermatitis, ichthyosis and xerosis, and ROS (reactive oxygen species) paly a role of skin toxicity. This study is focused on investigating the effect of ROS of applied acetone. Acetone was applied to mice skin (0.25ml/㎠) four times (6h, 12h, 18h, 24h) every day for two or four days. Increased activity of acid phosphatase (ACP) and increased content of lipid peroxide (LPO) in acetone was determined in the applied group for four days(4ACE) compared with the acetone applied group for two days (2ACE). As for the ROS generating enzymes, one of them, xanthine oxidase (XO) showed no differences between control and 2ACE despite the significantly different 4ACE. There were some differences between 2ACE and 4ACE on the activities of cytochrome P450 dependent aniline hydroxylase (CYPdAH), which seemed to be the increased rates of acetone metabolites. There were more decreased rates of the activities of ROS scavenging enzymes, glutathione peroxidase (GPx), catalase (CAT), superoxide dismutae (SOD), glutathione S-transferase (GST), and glutathione (GSH) contents in 4ACE compared with 2ACE. The results indicate that the damaged skin tissue could cause unbalance of the ROS generating system and scavenging system by the frequent exposure of acetone application.

Transcriptome analysis of Arabidopsis thaliana in response to cement dust

Cement dust is a major particulate air pollutants and can cause negative impacts on plant growth and development. The molecular bases of plant responses to cement dust are not elucidated. Therefore, a transcriptome analysis of Arabidopsis in response to cement dust was performed. In the present study, seedlings of Arabidopsis thaliana were exposed to cement dust at a rate of 1.5 g per 1 m2 area. Total RNA from control and cement-dust treated plants were used for transcriptome analysis using GeneChip® Arabidopsis ATH1 Genome Array. In response to cement dust application, the transcriptional profiling identified 1599 differentially expressed genes (DEGs) using a two-fold cutoff. Of these DEGs, 831 were up-regulated, and 768 were down-regulated. Differential expression of 15 genes from this list was validated using qRT-PCR. Gene ontology analysis using AgriGo program revealed that a large proportion of up-regulated DEGs are related to response to stimulus, response to stress, response to chemical stimulus, transcription factor activity, hydrolase activity, and carboxylesterase activity. While, a large proportion of down-regulated DEGs were mainly in the following categories: biosynthetic process, biological regulation, and response to stimulus, nucleic acid binding, transcription regulator activity, transcription factor activity, organelle lumen, nuclear lumen, and nucleolus. The DEGs up-regulated in response to cement dust include a set of reactive oxygen species scavenging enzymes (e.g., ascorbate peroxidase 2, peroxidases, glutathione S-transferases), heat shock proteins, late embryogenesis abundant proteins, ∆1-pyrroline-5-carboxylate synthase 1, as well as transcription factor genes of different families. This study is the first to provide a global view of the transcriptomic profiling of Arabidopsis in response to cement dust. The results will be helpful for better understanding the molecular basis for plant responses to cement dust pollution.

Effect of sodium nitroprusside on responses of Melissa officinalis to bicarbonate exposure and direct Fe deficiency stress

In our study, one-month-old Melissa officinalis plants were subjected to Fe-deficiency treatments, such as 10 µM Fe (as direct iron deficiency, DD), and 30 µM Fe + 10 mM NaHCO3 + 0.5 g l−1 CaCO3 (as indirect iron deficiency, ID), and 30 µM Fe (as control) for 14 d. Both Fe-deficiency types reduced plant growth, photosynthetic pigment contents, an active Fe content in roots and leaves, root Fe(III)-reducing capacity, Fe-use efficiency, maximal quantum yield of PSII photochemistry, a ratio of variable to basic fluorescence, and activities of antioxidant enzymes, while they increased lipid peroxidation and a H2O2 content in leaves. These effects were more pronounced in plants exposed to ID with bicarbonate than those of DD plants. We showed that sodium nitroprusside (SNP), as NO donor, could ameliorate the adverse effects of bicarbonate on above traits. The methylene blue, as NO blocker, reversed the protective effects conferred by SNP in the ID-treated plants as well as DD plants. These findings suggests that NO protects photosynthesis and growth of IDtreated plants as well as DD plants by contribution in availability and/or delivery of metabolically active iron or by changing activities of reactive oxygen species-scavenging enzymes.

Chilling-responsive mechanisms in halophyte Puccinellia tenuiflora seedlings revealed from proteomics analysis

Alkali grass (Puccinellia tenuiflora), a monocotyledonous perennial halophyte species, is a good pasture with great nutritional value for livestocks. It can thrive under low temperature in the saline-alkali soil of Songnen plain in northeastern China. In the present study, the chilling-responsive mechanism in P. tenuiflora leaves was investigated using physiological and proteomic approaches. After treatment of 10°C for 10 and 20days, photosynthesis, biomass, contents of osmolytes and antioxidants, and activities of reactive oxygen species scavenging enzymes were analyzed in leaves of 20-day-old seedlings. Besides, 89 chilling-responsive proteins were revealed from proteomic analysis. All the results highlighted that the growth of seedlings was inhibited due to chilling-decreased enzymes in photosynthesis, carbohydrate metabolism, and energy supplying. The accumulation of osmolytes (i.e., proline, soluble sugar, and glycine betaine) and enhancement of ascorbate–glutathione cycle and glutathione peroxidase/glutathione S-transferase pathway in leaves could minimize oxidative damage of membrane and other molecules under the chilling conditions. In addition, protein synthesis and turnover in cytoplasm and chloroplast were altered to cope with the chilling stress. This study provides valuable information for understanding the chilling-responsive and cross-tolerant mechanisms in monocotyledonous halophyte plant species.

Fibre elongation requires normal redox homeostasis modulated by cytosolic ascorbate peroxidase in cotton (Gossypium hirsutum).

High-quality cotton fibre equates to a more comfortable textile. Fibre length is an important index of fibre quality. Hydrogen peroxide (H2O2) acts as a signalling molecule in the regulation of fibre elongation. Results from in vitro ovule culture suggest that the alteration of fibre cell H2O2 levels affects fibre development. Ascorbate peroxidase (APX) is an important reactive oxygen species (ROS) scavenging enzyme, and we found that GhAPX1AT/DT encoded one member of the previously unrealized group of cytosolic APXs (cAPXs) that were preferentially expressed during the fibre elongation stage. Transgenic cottons with up- and down-regulation of GhAPX1AT/DT were generated to control fibre endogenous levels of H2O2 Suppression of all cAPX (IAO) resulted in a 3.5-fold increase in H2O2 level in fibres and oxidative stress, which significantly suppressed fibre elongation. The fibre length of transgenic lines with over-expression or specific down-regulation of GhAPX1AT/DT did not show any obvious change. However, the fibres in the over-expression lines exhibited higher tolerance to oxidative stress. Differentially expressed genes (DEGs) in fibres at 10 days post-anthesis (DPA) of IAO lines identified by RNA-seq were related to redox homeostasis, signalling pathways, stress responses and cell wall synthesis, and the DEGs that were up-regulated in IAO lines were also up-regulated in the 10 DPA and 20 DPA fibres of wild cotton compared with domesticated cotton. These results suggest that optimal H2O2 levels and redox state regulated by cytosolic APX are key mechanisms regulating fibre elongation, and dysregulation of the increase in H2O2 induces oxidative stress and results in shorter fibres by initiating secondary cell wall-related gene expression.