Project description:Hydrogen peroxide (H2O2) can act as a signaling molecule that influences various aspects of plant growth and development, including stress signaling and cell death. To unravel the molecular mechanisms that regulate the response towards an impact of increased H2O2 levels in plant cells, we focused on the photorespiration-dependent peroxisomal H2O2 production in Arabidopsis thaliana mutants lacking CATALASE2 (CAT2) activity (cat2-2) and screened for second-site mutations that attenuate the Fv'/Fm' decrease and lesion formation linked to the cat2-2 phenotype. A mutation in the transcriptional regulator SHORT-ROOT (SHR) of the GRAS family rescued the cell death phenotype of cat2-2 plants under photorespiration-promoting conditions in a SCR-independent way, and provoked perturbation of photorespiratory metabolites. SHR deficiency boosted ascorbate levels and prevented the oxidation of the glutathione pool in cat2-2 background upon exposure to photorespiratory stress. These results reveal an unanticipated role for SHR as a regulator of cellular redox homeostasis. Unstressed and stressed samples of 4 genotypes (Col-0, cat2, shr and cat2 shr) in triplicate
Project description:Hydrogen peroxide (H2O2) can act as a signaling molecule that influences various aspects of plant growth and development, including stress signaling and cell death. To unravel the molecular mechanisms that regulate the response towards an impact of increased H2O2 levels in plant cells, we focused on the photorespiration-dependent peroxisomal H2O2 production in Arabidopsis thaliana mutants lacking CATALASE2 (CAT2) activity (cat2-2) and screened for second-site mutations that attenuate the Fv'/Fm' decrease and lesion formation linked to the cat2-2 phenotype. A mutation in the transcriptional regulator SHORT-ROOT (SHR) of the GRAS family rescued the cell death phenotype of cat2-2 plants under photorespiration-promoting conditions in a SCR-independent way, and provoked perturbation of photorespiratory metabolites. SHR deficiency boosted ascorbate levels and prevented the oxidation of the glutathione pool in cat2-2 background upon exposure to photorespiratory stress. These results reveal an unanticipated role for SHR as a regulator of cellular redox homeostasis.
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: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. Three-week-old cat2-2 and shr-6/cat2-2 plants were exposed to photorespiratory conditions. Rosettes were sampled in three biological replicates before (T = 0) and after 24 hours (T = 24H) of the treatment. Total RNA was extracted with Spectrum Plant Total RNA Kit (Sigma) and submitted to Arabidopsis ATH1 microarray hybridization.
Project description:Hydrogen peroxide (H2O2) can act as a signaling molecule that influences various aspects of plant growth and development, including stress signaling and cell death. To unravel the molecular mechanisms that regulate the response towards an impact of increased H2O2 levels in plant cells, we focused on the photorespiration-dependent peroxisomal H2O2 production in Arabidopsis thaliana mutants lacking CATALASE2 (CAT2) activity (cat2-2) and screened for second-site mutations that attenuate the Fv'/Fm' decrease and lesion formation linked to the cat2-2 phenotype. A mutation in GLYCOLATE OXIDASE 1, encoding one of the two photorespiratory isoforms of glycolate oxidase rescued the cell death phenotype of cat2-2 plants under photorespiration-promoting conditions. Interestingly, introduction of gox2 into the cat2 background did not have the same effect and the double cat2 gox2 mutants were as affected as the parental cat2 mutants under conditions promoting photorespiration. Using a series of physiological, biochemical and metabolomic approaches we investigated the differential photorespiratory response of cat2 mutants underlied by the lack of GOX1 and GOX2. These differences are in line with the non-redundant functions of GOX1 and GOX2 which could be observed under enhanced photorespiration.
Project description:Hydrogen peroxide (H2O2) can act as a signaling molecule that influences various aspects of plant growth and development, including stress signaling and cell death. To unravel the molecular mechanisms that regulate the response towards an impact of increased H2O2 levels in plant cells, we focused on the photorespiration-dependent peroxisomal H2O2 production in Arabidopsis thaliana mutants lacking CATALASE2 (CAT2) activity (cat2-2) and screened for second-site mutations that attenuate the Fv'/Fm' decrease and lesion formation linked to the cat2-2 phenotype. A mutation in GLYCOLATE OXIDASE 1, encoding one of the two photorespiratory isoforms of glycolate oxidase rescued the cell death phenotype of cat2-2 plants under photorespiration-promoting conditions. Interestingly, introduction of gox2 into the cat2 background did not have the same effect and the double cat2 gox2 mutants were as affected as the parental cat2 mutants under conditions promoting photorespiration. Using a series of physiological, biochemical and metabolomic approaches we investigated the differential photorespiratory response of cat2 mutants underlied by the lack of GOX1 and GOX2. These differences are in line with the non-redundant functions of GOX1 and GOX2 which could be observed under enhanced photorespiration. Unstressed and stressed samples of cat2 gox1 and cat2 gox2 double mutants in triplicate
Project description:Hydrogen peroxide (H2O2) can act as a signaling molecule that influences various aspects of plant growth and development, including stress signaling and cell death. Catalase deficient plants are pioneering systems which accumulate hydrogen peroxide (H2O2) from peroxisomal origin during photorespiratory challenges. Respiratory burst oxidase homologues D and F are known to participate in intracellular oxidative stress response launched in cat2 mutants (Chaouch et al., 2012). We studied the compared the transcriptional response of cat2 rbohD and cat2 rbohF double mutants versus the cat2 background to further adress their role during photorespiratory stress.
Project description:The high metabolic flux through photorespiration constitutes a significant part of the carbon cycle. Although, the major enzymatic steps of the photorespiratory pathway are well characterized, little information is available on the functional significance of photorespiration beyond carbon recycling. Particularly important in this respect is the peroxisomal catalase activity which removes photorespiratory H2O2 generated during the oxidation of glycolate to glyoxylate, thus maintaining the cellular redox homeostasis governing the perception, integration and execution of stress responses. By perfroming a chemical screen, we identified 34 small molecules that alleviate the negative effects of photorespiration in Arabidopsis thaliana mutants lacking photorespiratory catalase (cat2). The chlorophyll fluorescence parameter photosystem II maximum efficiency (Fv'/Fm') was used as a high-throughput readout. The most potent chemical that could rescue the photorespiratory phenotype of cat2 is a pro-auxin that contains a synthetic auxin-like substructure belonging to the phenoxy herbicide family which can be released in planta. The naturally occurring indole-3-acetic acid (IAA) and other chemically distinct synthetic auxins also inhibited the photorespiratory-dependent cell death in cat2 mutants, implying a role for auxin signaling in stress tolerance. We used global transcriptome profiling to characterize the effect of a novel pro-axin structure (2-(2,4-dichlorophenoxy)-N-[4-(isobutyrylamino)-3-methoxyphenyl]propanamide) on Arabidopsis Col0 seedlings
Project description:Hydrogen peroxide (H2O2) can act as a signaling molecule that influences various aspects of plant growth and development, including stress signaling and cell death. Catalase deficient plants are pioneering systems which accumulate hydrogen peroxide (H2O2) from peroxisomal origin during photorespiratory challenges. Respiratory burst oxidase homologues D and F are known to participate in intracellular oxidative stress response launched in cat2 mutants (Chaouch et al., 2012). We studied the compared the transcriptional response of cat2 rbohD and cat2 rbohF double mutants versus the cat2 background to further adress their role during photorespiratory stress. After 3 weeks of growth, leaf tissue from the three different genotypes was harvested in triplicate.