Project description:Study of the effect of cadmium on KO and overexpressor mutants of glycolate oxidase-GOX2, which is one of the main sources of H202 from peroxisomes. Reactive oxygen species (ROS) act as secondary messengers that can be sensed by specific redox sensitive proteins responsible for the activation of signal transduction culminating in altered gene expression. ROS, which are involved in different activities, elicit a wide range of protein modifications, which might elicit different gene expressions. The subcellular site, in which modifications in ROS/oxidation state occur, can also act as a specific cellular redox network signal. The chemical identity of ROS and their subcellular origin actually is a specific imprint on the transcriptome response. In recent years, a number of transcriptomic studies related to altered ROS metabolism in plant peroxisomes have been carried out. In this study, we made a meta-analysis of these transcriptomic findings to identify common transcriptional footprints for plant peroxisomal-dependent signaling at early and later time points. These footprints highlight the regulation of various metabolic pathways and gene families, which are also found in plant responses to several abiotic stresses. Major peroxisomal-dependent genes are associated with protein and endoplasmic reticulum (ER) protection at later stages of stress while, at earlier stages, these genes are related to hormone biosynthesis and signaling regulation. Further, in silico analyses allowed us to assign human orthologs to some of the peroxisomal-dependent genes, which are mainly associated with different cancer types pathologies. Peroxisomal footprints provide a valuable resource for assessing and supporting key peroxisomal functions in cellular metabolism under control and stress conditions across species.
Project description:Reactive oxygen species (ROS) are key signalling molecules that regulate growth and development and coordinate responses to biotic and abiotic stresses. ROS homeostasis is controlled through a complex network of ROS production and scavenging enzymes. Recently, the first genes involved in ROS perception and signal transduction have been identified and, currently, we are facing the challenge to uncover the other players within the ROS regulatory gene network. The specificity of ensuing cellular responses depends on the type of ROS and their subcellular production sites. Various experimental systems, including catalase-deficient plants, in combination with genome-wide expression studies demonstrated that increased hydrogen peroxide (H2O2) levels significantly affect the transcriptome of plants and are capable of launching both defence responses and cell death events. We used microarrays to assess differential gene expression provoked by H2O2 from plastid or peroxisomal origin, respectively.
Project description:Reactive oxygen species (ROS) are key signalling molecules that regulate growth and development and coordinate responses to biotic and abiotic stresses. ROS homeostasis is controlled through a complex network of ROS production and scavenging enzymes. Recently, the first genes involved in ROS perception and signal transduction have been identified and, currently, we are facing the challenge to uncover the other players within the ROS regulatory gene network. The specificity of ensuing cellular responses depends on the type of ROS and their subcellular production sites. Various experimental systems, including catalase-deficient plants, in combination with genome-wide expression studies demonstrated that increased hydrogen peroxide (H2O2) levels significantly affect the transcriptome of plants and are capable of launching both defence responses and cell death events. We used microarrays to assess differential gene expression provoked by H2O2 from plastid or peroxisomal origin, respectively. Columbia-0 (Col-0, wild type), catalase-deficient Salk plants (10-15% of wild-type catalase activity; cat2-2; N576998; (Queval et al., 2007)) and A. thaliana plants expressing glycolate oxidase in chloroplasts (GO5 plants; (Fahnenstich et al., 2008)) were grown in soil under a 16h light/8h dark regime at photosynthetically active photon flux densities (PPFD) of 75 µmol quanta m-2 s-1 at 22°C day/18°C night temperatures and a CO2 concentration of 3,000 ppm. After three weeks of growth, plants were transferred to ambient CO2 concentration (380 ppm) and the same PPFD. Whole rosettes were harvested at 0h and 8h after transfer. Control samples were harvested at 8 h from plants continuously maintained in high CO2.
Project description:Reactive oxygen species (ROS) act as secondary messengers that can be sensed by specific redox-sensitive proteins responsible for the activation of signal transduction culminating in altered gene expression. The subcellular site, in which modifications in the ROS/oxidation state occur, can also act as a specific cellular redox network signal. The chemical identity of ROS and their subcellular origin is actually a specific imprint on the transcriptome response. In recent years, a number of transcriptomic studies related to altered ROS metabolism in plant peroxisomes have been carried out. In this study, we conducted a meta-analysis of these transcriptomic findings to identify common transcriptional footprints for plant peroxisomal-dependent signaling at early and later time points. These footprints highlight the regulation of various metabolic pathways and gene families, which are also found in plant responses to several abiotic stresses. Major peroxisomal-dependent genes are associated with protein and endoplasmic reticulum (ER) protection at later stages of stress while, at earlier stages, these genes are related to hormone biosynthesis and signaling regulation. Furthermore, in silico analyses allowed us to assign human orthologs to some of the peroxisomal-dependent proteins, which are mainly associated with different cancer pathologies. Peroxisomal footprints provide a valuable resource for assessing and supporting key peroxisomal functions in cellular metabolism under control and stress conditions across species.
Project description:Distinct retrograde signaling pathways have been identified for several cellular organelles. These pathways are important to maintain the function of these organelles in response to organelle-specific stress. Using Caenorhabditis elegans, we show for the first time that such a retrograde signaling also exists for peroxisomes. Analysis of the C. elegans transcriptome revealed that peroxisomal import stress caused by the knock-down of the peroxisomal matrix protein import receptor prx-5/PEX5 induces the compensatory up-regulation of genes involved in defense response and lipid metabolic processes, especially peroxisomal beta oxidation. We, therefore, propose that the peroxisomal retrograde signaling participates in the maintenance of peroxisomal function in response to peroxisomal import stress.
Project description:The thiol redox state is a decisive functional characteristic of proteins in cell biology. Plasmatic cell compartments maintain a thiol-based redox regulatory network linked to the glutathione/glutathione disulfide couple (GSH/GSSG) and the NAD(P)H system. The basic network constituents are known and in vivo cell imaging with gene-encoded probes have revealed insight into the dynamics of the [GSH]2/[GSSG] redox potential, H2O2 and NAD(P)H+H+ in dependence on the metabolic and environmental conditions. Highly limited is our understanding of the contribution and interaction of the components in the network, also because of compensatory reactions in genetic approaches. Reconstituting the cytosolic network in vitro from fifteen recombinant proteins at in vivo concentrations, namely glutathione peroxidase-like (GPXL), peroxiredoxins (PRX), glutaredoxins (GRX), thioredoxins (TRX), NADPH-dependent thioredoxin reductase A (NTRA) and glutathione reductase (GR) and applying GRX1-roGFP2 or roGFP2-ORP1 as dynamic sensors, allows for monitoring the response to a single H2O2 pulse. The major change in thiol oxidation as visualized by targeted proteomics occurred in relevant peptides of GPXL, and to a lesser extent of PRX, while other Cys-containing peptides only showed small changes in redox state and protection. Titration of ascorbate peroxidase (APX2) into the system together with dehydroascorbate reductase (DHAR1) lowered the oxidation of the fluorescent sensors in the network, but was unable to suppress it. The results demonstrate the power of the network to detoxify H2O2, the partially independent branches of electron flow with significance for specific cell signaling and the importance of APX to modulate the signaling without suppressing it and shifting the burden to glutathione oxidation.
Project description:Light controls control a vast array of biological processes, including cell and organelle motility, stress responses, organismal development and the entrainment of circadian rhythms, that maintain diurnal cycles of activity in organisms from cyanobacteria to humans. Recent studies indicate that a type of antioxidant and signaling proteins, peroxiredoxins, sustain circadian rhythms independent of characterized circadian pacemakers in organisms from all the three kingdoms of life, suggesting a role for H2O2 production in circadian clocks. Whereas many circadian clocks involve photosensitive pigments such as melanopsin and cryptochromes it is unclear whether peroxiredoxins can respond to light stimuli and how they interact with global signaling networks regulating e.g. clocks and aging, such as cyclic AMP (cAMP)/protein kinase A (PKA). In yeast, that lacks decidated photoreceptors, blue light induces cAMP-PKA-dependent, nuclear accumulation of a transcription factor, Msn2. However, the mechanism by which light represses pathway activity to stimulate Msn2 nuclear translocation is unknown. Here we identify increased H2O2–production via a conserved peroxisomal oxidase as the cause of light-induced Msn2 nuclear concentration. The H2O2 signal is transduced by the catalytic cysteines of the peroxiredoxin Tsa1 that relieve Msn2 from inhibitory PKA phosphorylation causing its nuclear accumulation. We propose that yeast senses light via H2O2 and a peroxiredoxin to inhibit cAMP/PKA activity and our data form a framework for the study of light responses in cells lacking dedicated light receptors and cAMP-controlled biological rhythms in multicellular organisms.
Project description:Hydrogen peroxide (H2O2) is a potent signaling molecule influencing various aspects of plant growth and development. Its limited lifetime and specific production sites in the plant cell necessitate the existence of specialized mechanisms that relay H2O2-encoded information. To discover such mechanisms, we focused on peroxisomal H2O2 production triggered by enhanced photorespiration in Arabidopsis mutants lacking catalase activity (cat2-2), and looked for second-site mutations that attenuate the negative effects (Fv'/Fm' decline and lesion formation) of H2O2 build up. A mutation residing in the GRAS family transcriptional regulator SHORT-ROOT (SHR) was found to underlie the increased performance of cat2-2 knock-outs under photorespiratory stress. In contrast to shr, introduction of the scr mutation in cat2-2 background did not improve the photorespiratory performance of plants lacking peroxisomal catalase. The absence of SHR negatively affected the activity of the photorespiratory enzymes glycolate oxidase and catalase, which was accompanied with elevated glycolate content and inability to accumulate glycine under conditions promoting photorespiration. The transcriptome signature of cat2-2 shr-6 double mutants exposed to photorespiratory stress lacked jasmonate-dependent signaling components, otherwise induced in cat2-2. The photorespiratory phenotype of cat2-2 was found to be modulated by exogenous sugars both in the presence and absence of shr. Taken together, these findings highlight a crucial role for SHR in H2O2 signal transduction and stress tolerance.
Project description:The aim is to study the function of peroxisomal NAD-malate dehydrogenase in fatty acid beta-oxidation, glyoxylate cycle and photorespiration. Both peroxisomal MDH genes (At2g22780 and At5g09660) have been knocked out with T-DNA insertions and a double mutant made. Double mutant seedlings are blocked in beta-oxidation - they are 2,4DB resistant and beta-oxidation genes are repressed. They carry out glyoxylate cycle as normal. Plants grow well in soil and produce seed. Microarray analysis will tell us the extent of changes in gene expression in the mutant. For microarray analysis seeds are stratified at 4 C on agar medium with 1/2 strength M&S salts and 1% sucrose for 2 days, then seedlings grown for 2 days at 20 C in the light (100 umol/m2/s). Triplicate samples will be grown for mutant and wild type (col-0) and RNA isolated from each. Experimenter name = Itsara Pracharoenwattana Experimenter phone = 0131 650 5316 Experimenter fax = 0131 650 5392 Experimenter department = Institute of Molecular Plant Sciences Experimenter institute = University of Edinburgh Experimenter address = Daniel Rutherford Building University of Edinburgh Experimenter address = The King's Buildings Experimenter address = Edinburgh Experimenter zip/postal_code = EH9 3JH Experimenter country = UK Keywords: genetic_modification_design