Expression Of ROS-related Genes Research Articles

The role of reactive oxygen species in plant-virus interactions.

Reactive oxygen species (ROS) play a complex role in interactions between plant viruses and their host plants. They can both help the plant defend against viral infection and support viral infection and spread. This review explores the various roles of ROS in plant-virus interactions, focusing on their involvement in symptom development and the activation of plant defense mechanisms. The article discusses how ROS can directly inhibit viral infection, as well as how they can regulate antiviral mechanisms through various pathways involving miRNAs, virus-derived small interfering RNAs, viral proteins, and host proteins. Additionally, it examines how ROS can enhance plant resistance by interacting with hormonal pathways and external substances. The review also considers how ROS might promote viral infection and transmission, emphasizing their intricate role in plant-virus dynamics. These insights offer valuable guidance for future research, such as exploring the manipulation of ROS-related gene expression through genetic engineering, developing biopesticides, and adjusting environmental conditions to improve plant resistance to viruses. This framework can advance research in plant disease resistance, agricultural practices, and disease control.

An analysis of the prognostic role of reactive oxygen species-associated genes in breast cancer.

This study aimed to type breast cancer in relation to reactive oxygen species (ROS), clinical indicators, single nucleotide variant (SNV) mutations, functional differences, immune infiltration, and predictive responses to immunotherapy or chemotherapy, and constructing a prognostic model. We used uniCox analysis, ConsensusClusterPlus, and the proportion of ambiguous clustering (PAC) to analyze The Cancer Genome Atlas (TCGA) data to determine optimal groupings and obtain differentially expressed ROS-related genes. Clinical indicators were then combined with the classification results and the Chi-square test was used to assess differences. We further examined SNV mutations, and functional differences using gene set enrichment analysis (GSEA) analysis, the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, immune cell infiltration, and response to immunotherapy and chemotherapy. A prognostic model for breast cancer was constructed using these differentially expressed genes, immunotherapy or chemotherapy responses, and survival curves. RT-qPCR was used to detect the differences in the expression of LCE3D, CA1, PIRT and SMR3A in breast cancer cell lines and normal breast epithelial cell line. We identified two distinct tumor types with significant differences in ROS-related gene expression, clinical indicators, SNV mutations, functional pathways, and immune infiltration. The response to specific chemotherapy drugs and immunotherapy treatments also documented significant differences. The prognostic model constructed with 16 genes linked to survival could efficiently divide patients into high- and low-risk groups. The high-risk group showed a poorer prognosis, higher tumor purity, distinct immune microenvironment, and lower immunotherapy response. RT-qPCR results showed that LCE3D, CA1, PIRT and SMR3A are highly expressed in breast cancer. Our methodical examination presented an enhanced insight into the molecular and immunological heterogeneity of breast cancer. It can contribute to the understanding of prognosis and offer valuable insights for personalized treatment strategies. Further, the prognostic model can potentially serve as a powerful tool for risk stratification and therapeutic decision-making in clinical settings.

DNA methylation and lipid metabolism are involved in GA-induced maize aleurone layers PCD as revealed by transcriptome analysis

BackgroundThe aleurone layer is a part of many plant seeds, and during seed germination, aleurone cells undergo PCD, which is promoted by GA from the embryo. However, the numerous components of the GA signaling pathway that mediate PCD of the aleurone layers remain to be identified. Few genes and transcriptomes have been studied thus far in aleurone layers to improve our understanding of how PCD occurs and how the regulatory mechanism functions during PCD. Our previous studies have shown that histone deacetylases (HDACs) are required in GA-induced PCD of aleurone layer. To further explore the molecular mechanisms by which epigenetic modifications regulate aleurone PCD, we performed a global comparative transcriptome analysis of embryoless aleurones treated with GA or histone acetylase (HAT) inhibitors.ResultsIn this study, a total of 7,919 differentially expressed genes (DEGs) were analyzed, 2,554 DEGs of which were found to be common under two treatments. These identified DEGs were involved in various biological processes, including DNA methylation, lipid metabolism and ROS signaling. Further investigations revealed that inhibition of DNA methyltransferases prevented aleurone PCD, suggesting that active DNA methylation plays a role in regulating aleurone PCD. GA or HAT inhibitor induced lipoxygenase gene expression, leading to lipid degradation, but this process was not affected by DNA methylation. However, DNA methylation inhibitor could regulate ROS-related gene expression and inhibit GA-induced production of hydrogen peroxide (H2O2).ConclusionOverall, linking of lipoxygenase, DNA methylation, and H2O2 may indicate that GA-induced higher HDAC activity in aleurones causes breakdown of lipids via regulating lipoxygenase gene expression, and increased DNA methylation positively mediates H2O2 production; thus, DNA methylation and lipid metabolism pathways may represent an important and complex signaling network in maize aleurone PCD.

Evaluation of Fasting and Probiotics in Reducing Postweaning Stress in Rabbits: Study of their Effects on Biochemical and Gene expression Patterns

Postweaning stress in mammalian in vivo models leads to significant oxidative stress in the body as well as inducing hormonal disturbance. In this study, we assessed progressive alterations in reactive oxygen species (ROS), which at high levels can show oxidative stress, in addition to oxidative damage to the DNA structure of rabbits. Different groups of rabbits were fasted for 48 h per week for 3 weeks, fed a commercial diet with probiotics added (200 mg of Bacillus licheniformis and Bacillus subtilis), and fasted while being treated with probiotics. The results showed that weaning induced a significant elevation in oxidative stress markers, such as the ROS-related genes malate dehydrogenase 1 (MDH1) and flavin-containing monooxygenase 2 (FMO2), DNA damage, and hormonal disturbance. However, probiotic treatment resulted in significant decreases in the levels of malondialdehyde, cortisol, and triiodothyronine (T3); DNA damage; and apoptosis, as well as changes in the expression of ROS-related genes. On the other hand, supplementation with probiotics reduced these postweaning stress signs in fasted animal models by elevating the genes encoding catalase and superoxide dismutase as well as increasing glutathione peroxidase (GSH-Px), glutathione–s-transferase, alkaline phosphatase, glucose, and thyroxin (T4) levels. The results suggest that supplementation with probiotics accompanied by a fasting program could decrease oxidative stress, ROS genes, and genomic DNA damage and improve the hormonal status that is induced by postweaning stress in mammalian in vivo models.

Fumonisin B1 Biosynthesis Is Associated with Oxidative Stress and Plays an Important Role in Fusarium proliferatum Infection on Banana Fruit.

Fungal response to oxidative stress during infection on postharvest fruit is largely unknown. Here, we found that hydrogen peroxide (H2O2) treatment inhibited the growth of Fusarium proliferatum causing crown rot of banana fruit, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. H2O2 exposure increased endogenous reactive oxygen species (ROS) and fumonisin B1 (FB1) production in F. proliferatum, possibly by modulating FUM or ROS-related gene expression. Importantly, H2O2 treatment inhibited F. proliferatum growth in vivo but induced FB1 accumulation in banana peel. Finally, we constructed the FpFUM21 deletion mutant (ΔFpfum21) of F. proliferatum that was attenuated in FB1 biosynthesis and less tolerant to oxidative stress. Moreover, the ΔFpfum21 strain was less virulent compared to the wild type (WT) due to the inability to induce FB1 production in the banana host. These results suggested that FB1 biosynthesis is associated with oxidative stress in F. proliferatum and contributes to fungal infection on banana fruit.

In Vitro Expression Analysis of Cytokines and ROS-Related Genes in Human Corneal Fibroblasts and Keratocytes of Healthy and Keratoconus Corneas

ABSTRACT Purpose To investigate expression of cytokines and ROS-related genes in stromal cells of healthy and keratoconus (KC) corneas. Methods Expression analysis was performed for cytokines including several interleukins (IL), Tumor necrosis factor-α (TNF-α), Transforming growth factor-β1 (TGF-β1), Interferon-γ (IFN-γ) and ROS-related genes such as Catalase, Glutathione peroxidase 1, NADPH oxidase 1, superoxide dismutase 1 in corneal fibroblasts (HCFs/KC-HCFs) or keratocytes (Keratocytes/KC-Keratocytes) by qPCR and ELISA. Results Gene and protein expression of most inflammatory markers was decreased in keratocytes compared to fibroblasts, whereas no differences were found between healthy and keratoconus cells for the majority of cytokines measured. TNF-α expression was increased at gene (KC keratocytes) and protein levels (supernatant of Keratocytes/KC-Keratocytes) compared to corneal fibroblasts. No differential expression of ROS-related genes was detected between healthy and diseased cells in both fibroblasts and keratocytes. Conclusion Increased expression of several inflammatory markers described as altered in KC was not evident in KC cells in vitro.

Transcriptomics and Metabolomics of Reactive Oxygen Species Modulation in Near-Null Magnetic Field-Induced Arabidopsis thaliana.

The geomagnetic field (GMF) is a natural component of Earth's biosphere. GMF reduction to near-null values (NNMF) induces gene expression modulation that generates biomolecular, morphological, and developmental changes. Here, we evaluate the effect of NNMF on gene expression and reactive oxygen species (ROS) production in time-course experiments on Arabidopsis thaliana. Plants exposed to NNMF in a triaxial Helmholtz coils system were sampled from 10 min to 96 h to evaluate differentially expressed genes (DEGs) of oxidative stress responses by gene microarray. In 24-96 h developing stages, H2O2 and polyphenols were also analyzed from roots and shoots. A total of 194 DEGs involved in oxidative reactions were selected, many of which showed a fold change ≥±2 in at least one timing point. Heatmap clustering showed DEGs both between roots/shoots and among the different time points. NNMF induced a lower H2O2 than GMF, in agreement with the expression of ROS-related genes. Forty-four polyphenols were identified, the content of which progressively decreased during NNMF exposition time. The comparison between polyphenols content and DEGs showed overlapping patterns. These results indicate that GMF reduction induces metabolomic and transcriptomic modulation of ROS-scavenging enzymes and H2O2 production in A. thaliana, which is paralleled by the regulation of antioxidant polyphenols.

Do 50/60 Hz magnetic fields influence oxidative or DNA damage responses in human SH-SY5Y neuroblastoma cells?

Purpose We investigated the possible effects of 50 and 60 Hz magnetic fields (MFs) on reactive oxygen species (ROS) production, DNA damage, DNA damage repair rate, as well as gene expression related to oxidative stress and DNA damage signaling. Materials and methods Human SH-SY5Y neuroblastoma cells were sham-exposed or exposed to 100 µTRMS MFs for 24 h, then assayed or further treated with 100 µM menadione for 1 h before the assay. The levels of ROS and cytosolic superoxide anion (O2 •–) were assayed fluorometrically. DNA damage and gene expression were assayed by comet assay and RT-qPCR, respectively. To examine whether MFs affected DNA damage repair rate, cells were allowed to repair their DNA for 1 or 2 h after menadione treatment and then assayed for DNA damage. Results There was suggestive evidence of a general low-magnitude increase in the expression of ROS-related genes (primarily genes with antioxidant activity) when quantified immediately after MF exposure, suggesting a response to a small increase in ROS level. The possible upregulation of ROS-related genes is supported by the finding that the level of menadione-induced ROS was consistently decreased by 50 Hz MFs (not significantly by 60 Hz MFs) in several measurements 30–60 min after MF exposure. MF exposures did not affect cytosolic O2 •– levels, DNA damage, or its repair rate. Changes in the expression of DNA damage-signaling genes in the MF-exposed cells did not exceed the expected rate of false-positive findings. No firm evidence was found for differential effects from 50 vs. 60 Hz MFs. Conclusions While only weak effects were found on the endpoints measured, the results are consistent with MF effects on ROS signaling.

Survival of Plants During Short-Term BOA-OH Exposure: ROS Related Gene Expression and Detoxification Reactions Are Accompanied With Fast Membrane Lipid Repair in Root Tips

For the characterization of BOA-OH insensitive plants, we studied the time-dependent effects of the benzoxazolinone-4/5/6/7-OH isomers on maize roots. Exposure of Zea mays seedlings to 0.5 mM BOA-OH elicits root zone-specific reactions by the formation of dark rings and spots in the zone of lateral roots, high catalase activity on root hairs, and no visible defense reaction at the root tip. We studied BOA-6-OH- short-term effects on membrane lipids and fatty acids in maize root tips in comparison to the benzoxazinone-free species Abutilon theophrasti Medik. Decreased contents of phosphatidylinositol in A. theophrasti and phosphatidylcholine in maize were found after 10–30 min. In the youngest tissue, α-linoleic acid (18:2), decreased considerably in both species and recovered within one hr. Disturbances in membrane phospholipid contents were balanced in both species within 30–60 min. Triacylglycerols (TAGs) were also affected, but levels of maize diacylglycerols (DAGs) were almost unchanged, suggesting a release of fatty acids for membrane lipid regeneration from TAGs while resulting DAGs are buildings blocks for phospholipid reconstitution, concomitant with BOA-6-OH glucosylation. Expression of superoxide dismutase (SOD2) and of ER-bound oleoyl desaturase (FAD2-2) genes were contemporaneously up regulated in contrast to the catalase CAT1, while CAT3 was arguably involved at a later stage of the detoxification process. Immuno-responses were not elicited in short-terms, since the expression of NPR1, POX12 were barely affected, PR4 after 6 h with BOA-4/7-OH and PR1 after 24 h with BOA-5/6-OH. The rapid membrane recovery, reactive oxygen species, and allelochemical detoxification may be characteristic for BOA-OH insensitive plants.

Genome-wide analysis of ZAT gene family revealed GhZAT6 regulates salt stress tolerance in G. hirsutum

High salt environments can induce stress in different plants. The genes containing the ZAT domain constitute a family that belongs to a branch of the C2H2 family, which plays a vital role in responding to abiotic stresses. In this study, we identified 169 ZAT genes from seven plant species, including 44 ZAT genes from G. hirsutum. Phylogenetic tree analysis divided ZAT genes in six groups with conserved gene structure, protein motifs. Two C2H2 domains and an EAR domain and even chromosomal distribution on At and Dt sub-genome chromosomes of G. hirsutum was observed. GhZAT6 was primarily expressed in the root tissue and responded to NaCl and ABA treatments. Subcellular localization found that GhZAT6 was located in the nucleus and demonstrated transactivation activity during a transactivation activity assay. Arabidopsis transgenic lines overexpressing the GhZAT6 gene showed salt tolerance and grew more vigorously than WT on MS medium supplemented with 100 mmol NaCl. Additionally, the silencing of the GhZAT6 gene in cotton plants showed more obvious leaf wilting than the control plants, which were subjected to 400 mmol NaCl treatment. Next, the expressions of GhAPX1, GhFSD1, GhFSD2, and GhSOS3 were significantly lower in the GhZAT6-silenced plants treated with NaCl than the control. Based on these findings, GhZAT6 may be involved in the ABA pathway and mediate salt stress tolerance by regulating ROS-related gene expression.

Cold-Triggered Induction of ROS- and Raffinose Metabolism in Freezing-Sensitive Taproot Tissue of Sugar Beet.

Sugar beet (Beta vulgaris subsp. vulgaris) is the exclusive source of sugar in the form of sucrose in temperate climate zones. Sugar beet is grown there as an annual crop from spring to autumn because of the damaging effect of freezing temperatures to taproot tissue. A collection of hybrid and non-hybrid sugar beet cultivars was tested for winter survival rates and freezing tolerance. Three genotypes with either low or high winter survival rates were selected for detailed study of their response to frost. These genotypes differed in the severity of frost injury in a defined inner region in the upper part of the taproot, the so-called pith. We aimed to elucidate genotype- and tissue-dependent molecular processes during freezing and combined analyses of sugar beet anatomy and physiology with transcriptomic and metabolite profiles of leaf and taproot tissues at low temperatures. Freezing temperatures induced strong downregulation of photosynthesis in leaves, generation of reactive oxygen species (ROS), and ROS-related gene expression in taproots. Simultaneously, expression of genes involved in raffinose metabolism, as well as concentrations of raffinose and its intermediates, increased markedly in both leaf and taproot tissue at low temperatures. The accumulation of raffinose in the pith tissue correlated with freezing tolerance of the three genotypes. We discuss a protective role for raffinose and its precursors against freezing damage of sugar beet taproot tissue.

Human Endogenous Retrovirus (HERV)-K env Gene Knockout Affects Tumorigenic Characteristics of nupr1 Gene in DLD-1 Colorectal Cancer Cells.

Human endogenous retroviruses (HERVs) are suggested to be involved in the development of certain diseases, especially cancers. To elucidate the function of HERV-K Env protein in cancers, an HERV-K env gene knockout (KO) in DLD-1 colorectal cancer cell lines was generated using the CRISPR-Cas9 system. Transcriptome analysis of HERV-K env KO cells using next-generation sequencing (NGS) was performed to identify the key genes associated with the function of HERV-K Env protein. The proliferation of HERV-K env KO cells was significantly reduced in in vitro culture as well as in in vivo nude mouse model. Tumorigenic characteristics, including migration, invasion, and tumor colonization, were also significantly reduced in HERV-K env KO cells. Whereas, they were enhanced in HERV-K env over-expressing DLD-1 cells. The expression of nuclear protein-1 (NUPR1), an ER-stress response factor that plays an important role in cell proliferation, migration, and reactive oxygen species (ROS) generation in cancer cells, significantly reduced in HERV-K env KO cells. ROS levels and ROS-related gene expression was also significantly reduced in HERV-K env KO cells. Cells transfected with NUPR1 siRNA (small interfering RNA) exhibited the same phenotype as HERV-K env KO cells. These results suggest that the HERV-K env gene affects tumorigenic characteristics, including cell proliferation, migration, and tumor colonization through NUPR1 related pathway.

Daily rhythms of phytomelatonin signaling modulate diurnal stomatal closure via regulating reactive oxygen species dynamics in Arabidopsis.

Melatonin is a well-studied neurohormone oscillating in a 24-h cycle in vertebrates. Phytomelatonin is widespread in plant kingdom, but it remains elusive whether this newly characterized putative hormone underlies the regulation by daily rhythms. Here, we report phytomelatonin signaling, as reflected by changes in endogenous concentrations of phytomelatonin and expression of genes associated with biosynthesis of phytomelatonin (AtSNAT1, AtCOMT1, and AtASMT) and its receptor (AtPMTR1), shows 24-h oscillations in Arabidopsis. The variation of reactive oxygen species (ROS) production and scavenging and expression of ROS-related genes significantly decrease in pmtr1 and snat and increase in PMTR1-OE seedlings, indicating the rhythmicity in phytomelatonin signaling is required for maintenance of ROS dynamics. Additionally, the ROS signaling feedback influences the expression of AtSNAT1, AtCOMT1, AtASMT, and AtPMTR1, suggesting the phytomelatonin and ROS signaling are coordinately interrelated. The pmtr1 mutant plants lose diurnal stomatal closure, with stomata remaining open during daytime as well as nighttime and mutants showing more water loss and drought sensitivity when compared with the wild-type Col-0 plants. Taken together, our results suggest that PMTR1-regulated ROS signaling peaks in the afternoon and may transmit the darkness signals to trigger stomatal closure, which might be essential for high water-use efficiency and drought tolerance.

The therapeutic role of baicalein in combating experimental periodontitis with diabetes via Nrf2 antioxidant signaling pathway.

Oxidative stress has been suggested as an important pathogenic factor contributing to chronic periodontitis with diabetes mellitus (CPDM). Previous studies have revealed the potential therapeutic properties of baicalein (BCI) in oxidative stress-related diseases; however, the antioxidant effects of BCI on therapy for individual with CPDM remain largely unexplored. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in cellular defence against oxidative stress. In this study, we aim to determine whether BCI prevents diabetes-related periodontal tissue destruction by regulating Nrf2 signaling pathway. Human gingival epithelial cells (hGECs) were challenged with high glucose (HG, 25mmol/L) and/or lipopolysaccharide (LPS, 20µg/mL). Reactive oxygen species (ROS) were detected by fluorescence-activated cell sorting. The changes of antioxidant-related genes, including Nrf2, catalase (Cat), glutamate-cysteine ligase catalytic subunit (Gclc), superoxide dismutase 1 (Sod1), and superoxide dismutase 2 (Sod2), were quantified by real-time PCR. The localization of phospho-Nrf2 (pNrf2, S40) in the nucleus was detected by immunofluorescence staining and laser scanning confocal microscope (LSCM). PNrf2 and total form of Nrf2 were determined usingwestern blot. The above indicators together with mitochondrial membrane potential (MMP) were further investigated in hGECs pre-treated with different concentrations of BCI (0.01, 0.1, or 0.5µg/mL) before stimulated with HG plus LPS (GP). Finally, the role of BCI in activating Nrf2 signaling pathway and relieving the alveolar bone absorption was examined in the CPDM model of Sprague Dawley rats. CPDM rats were oral gavaged with BCI (50, 100, or 200mg/kg daily). The pNrf2 was detected by immunohistochemistry, and the alveolar bone absorption was examined by microcomputed tomography. Our results showed that ROS were significantly increased in both groups of HG and LPS, with the strongest generation in the GP group. In terms of ROS-related gene expression, we found that the mRNA levels of Nrf2, Cat, Gclc, Sod1, and Sod2 were significantly decreased in HG and LPS groups. In consistent with the strongest induction of ROS in GP group, the gene expression in GP group was further decreased as compared to those of HG and LPS groups. Also, the expression of pNrf2 exhibited the same trend with the expression of those antioxidant genes. However, the generation of ROS and the loss of mitochondrial membrane potential induced by GP were abolished by pre-treatment with different concentrations of BCI (0.01, 0.1, or 0.5µg/mL). Interestingly, we observed that BCI promoted the nucleus translocation of pNrf2, as well as the gene expression levels of pNrf2 and its target genes (Cat, Gclc, Sod1, and Sod2). Finally, in the CPDM animal model, we found that BCI (at concentrations: 50, 100, and 200mg/kg) markedly increased the number of pNrf2-positive cells in periodontal tissue and mitigated the alveolar bone loss. Our data revealed a potential role for clinic application of BCI under CPDM conditions, suggesting a new therapeutic drug for CPDM patients.

Overexpressing sweetpotato peroxidase gene swpa4 affects nitric oxide production by activating the expression of reactive oxygen species- and nitric oxide-related genes in tobacco

Reactive oxygen species (ROS) and nitric oxide (NO) are key signaling molecules involved in various developmental and stress responses in plants. NO and ROS production, which is triggered by various stimuli, activates downstream signaling pathways to help plants cope with abiotic and biotic stresses. Recent evidence suggests that the interplay between NO and ROS signaling plays a critical role in regulating stress responses. However, the underlying molecular mechanism remains poorly understood. We previously reported that transgenic tobacco overexpressing the swpa4 peroxidase (POD) gene from sweetpotato exhibits increased tolerance to stress. Overexpression of swpa4 also induces the generation of H2O2 and activates the expression of various extracellular acidic pathogenesis-related (PR) genes. Here, we show that swpa4 positively regulates the expression of ROS- and NO-related genes in transgenic tobacco plants. Plants expressing swpa4 exhibited increased expression of ROS-related genes and increased ROS-related enzyme activity under normal conditions and H2O2 treatment, whereas the expression of NO associated 1 (NOA1) only increased under normal conditions. Moreover, plants overexpressing swpa4 showed increased NO levels under normal conditions and after treatment with the NO donor sodium nitroprusside (SNP). Interestingly, treatment with a POD inhibitor dramatically reduced NO levels in swpa4 transgenic plants. These findings suggest that swpa4 regulates H2O2 and NO homeostasis in plants under stress conditions, thereby establishing a possible molecular link between the NO and ROS signaling pathways.

A Raf-like MAPKKK gene, GhRaf19, negatively regulates tolerance to drought and salt and positively regulates resistance to cold stress by modulating reactive oxygen species in cotton

Mitogen-activated protein kinase kinase kinases (MAPKKKs) function at the top level of MAPK cascades and play important roles in plant development and stress responses. Although MAPKKKs comprise the largest family in the MAPK cascades, very few Raf-like MAPKKKs have been functionally identified, especially in the economically important crop cotton. In this study, a Raf-like MAPKKK gene, GhRaf19, was characterized for the first time in cotton. Our data show that the expression of GhRaf19 was inhibited by PEG and NaCl and induced by cold (4°C) and H2O2. Furthermore, when GhRaf19 was silenced in cotton using virus-induced gene silencing (VIGS), tolerance to drought and salt stress were enhanced, the accumulation of reactive oxygen species (ROS) was reduced, and ROS-related gene expression was increased. Consistent with these results, in N. benthamiana, overexpressing-GhRaf19 reduced tolerance to drought and salt. However, GhRaf19-silenced plants showed lowered resistance to cold in cotton, and this effect was correlated with the accumulation of ROS. In contrast, overexpressing GhRaf19 in N. benthamiana increased resistance to cold by inducing higher levels of expression and activity of ROS-related antioxidant genes/enzymes. These results indicate that GhRaf19 negatively regulates tolerance to drought and salt and positively regulates resistance to cold stress by modulating cellular ROS in cotton.

SpBADH of the halophyte Sesuvium portulacastrum strongly confers drought tolerance through ROS scavenging in transgenic Arabidopsis

Glycine betaine (GB) accumulation is involved in abiotic stress. However, it is not known whether BADH, the key enzyme of GB synthesis, utilizes the antioxidant system to confer drought stress tolerance. In this study, a novel member of the ALDH10 gene family, SpBADH, was isolated from Sesuvium portulacastrum. The expression of this gene was up-regulated by NaCl, PEG6000, H2O2, ABA and high temperature in S. portulacastrum. SpBADH overexpression in Arabidopsis resulted in higher BADH activity and GB content and might increase tolerance to drought/osmotic stresses, specifically strong tolerance to drought stress. Transgenic lines exhibited lower MDA and H2O2 contents but higher proline, POD, SOD and CAT contents than the wild type under drought and osmotic stresses. SpBADH overexpression in Arabidopsis also enhanced the expression of ROS-related genes including AtSOD, AtPOD, AtCAT, AtAPX and Atpsb under drought and osmotic stresses. Thus, SpBADH increases plant tolerance to drought or osmotic stresses by reducing H2O2, increasing proline, and activating antioxidative enzymes to improve ROS scavenging.

A Novel Pyrimidin-Like Plant Activator Stimulates Plant Disease Resistance and Promotes Growth

Plant activators are chemicals that induce plant defense responses to a broad spectrum of pathogens. Here, we identified a new potential plant activator, 5-(cyclopropylmethyl)-6-methyl-2-(2-pyridyl)pyrimidin-4-ol, named PPA (pyrimidin-type plant activator). Compared with benzothiadiazole S-methyl ester (BTH), a functional analog of salicylic acid (SA), PPA was fully soluble in water and increased fresh weight of rice (Oryza sativa) and Arabidopsis plants at low concentrations. In addition, PPA also promoted lateral root development. Microarray data and real-time PCR revealed that PPA-treated leaves not challenged with pathogen showed up-regulation of genes related to reactive oxygen species (ROS), defenses and SA. During bacterial infection, Arabidopsis plants pretreated with PPA showed dramatically decreased disease symptoms and an earlier and stronger ROS burst, compared with plants pretreated with BTH. Microscopy revealed that H2O2 accumulated in the cytosol, plasma membrane and cell wall around intracellular bacteria, and also on the bacterial cell wall, indicating that H2O2 was directly involved in killing bacteria. The increase in ROS-related gene expression also supported this observation. Our results indicate that PPA enhances plant defenses against pathogen invasion through the plant redox system, and as a water-soluble compound that can promote plant growth, has broad potential applications in agriculture.

Enhanced aphid detoxification when confronted by a host with elevated ROS production

Reactive oxygen species (ROS) plays an important role in plant defense responses against bacteria, fungi and insect pests. Most recently, we have demonstrated that loss of Arabidopsis thaliana BOTRYTIS-INDUCED KINASE1 (BIK1) function releases its suppression of aphid-induced H2O2 production and cell death, rendering the bik1 mutant more resistant to green peach aphid (Myzus persicae) than wild-type plants. However, little is known regarding how ROS-related gene expression is correlated with bik1-mediated resistance to aphids, or whether these aphids biochemically respond to the oxidative stress. Here, we show that the bik1 mutant exhibited elevated basal expression of ROS-generating and -responsive genes, but not ROS-metabolizing genes. Conversely, we detected enhanced detoxification enzymatic activities in aphids reared on bik1 plants compared to those on wild-type plants, suggesting that aphids counter the oxidative stress associated with bik1 through elevated metabolic resistance.

GhWRKY68 reduces resistance to salt and drought in transgenic Nicotiana benthamiana.

The WRKY transcription factors modulate numerous physiological processes, including plant growth, development and responses to various environmental stresses. Currently, our understanding of the functions of the majority of the WRKY family members and their possible roles in signalling crosstalk is limited. In particular, very few WRKYs have been identified and characterised from an economically important crop, cotton. In this study, we characterised a novel group IIc WRKY gene, GhWRKY68, which is induced by different abiotic stresses and multiple defence-related signalling molecules. The β-glucuronidase activity driven by the GhWRKY68 promoter was enhanced after exposure to drought, salt, abscisic acid (ABA) and H2O2. The overexpression of GhWRKY68 in Nicotiana benthamiana reduced resistance to drought and salt and affected several physiological indices. GhWRKY68 may mediate salt and drought responses by modulating ABA content and enhancing the transcript levels of ABA-responsive genes. GhWRKY68-overexpressing plants exhibited reduced tolerance to oxidative stress after drought and salt stress treatments, which correlated with the accumulation of reactive oxygen species (ROS), reduced enzyme activities, elevated malondialdehyde (MDA) content and altered ROS-related gene expression. These results indicate that GhWRKY68 is a transcription factor that responds to drought and salt stresses by regulating ABA signalling and modulating cellular ROS.