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.
The ROS Wheel: Refining ROS Transcriptional Footprints.
Age
View SamplesHydrogen 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.
The ROS Wheel: Refining ROS Transcriptional Footprints.
Age, Specimen part, Treatment, Time
View SamplesSix weeks old Arabidopsis plants were transferred to a low CO2 (100 ppm) environment during 24 hours and compared to control plants kept under ambient CO2 conditions. Limited CO2 availability will cause higher rates of photorespiration and affect the plant redox homeostasis. We studied the transcriptomic impact of exposing plants to a lower CO2 environment to further eliculidate the signaling pathways during photorespiratory stress.
The ROS Wheel: Refining ROS Transcriptional Footprints.
Age, Treatment
View SamplesExcessive levels of reactive oxygen species (ROS) cause cellular stress through damage to all classes of macromolecules and result in cell death. However, ROS can also act as signaling molecules in various biological processes. In plants, ROS signaling has been documented in environmental stress perception, plant development and cell death amongst others. Knowledge on the regulatory events governing ROS signal transduction is however still scratching the surface. To further elucidate the transcriptional response and regulation upon ROS accumulation we supplemented Arabidopsis seedlings with a 10mM hydrogen peroxide (H2O2) solution to trigger oxidative stress.
The ROS Wheel: Refining ROS Transcriptional Footprints.
Age, Specimen part
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The transcription factor ABI4 Is required for the ascorbic acid-dependent regulation of growth and regulation of jasmonate-dependent defense signaling pathways in Arabidopsis.
Age, Specimen part
View SamplesThe role of abscisic acid (ABA) signalling in the ascorbic acid (AA)-dependent control of plant growth and defence was determined using the vtc1 and vtc2 mutants, which have impaired ascorbic acid synthesis, and in the abi4 mutant that is impaired in ABA-signalling. ABA levels were increase in the mutants relative to the wild type (Col0). Like vtc1 the vtc2 mutants have a slow growth relative to Col0. However, the wild type phenotype is restored in the abi4vtc2 double mutant. Similarly, the sugar sensing phenotype of in the abi4 is reversed in the abi4vtc2 double mutant. The vtc1 and vtc2 leaf transcriptomes show up to 70 % homology with abi4. Of the transcripts that are altered in the mutants a relative to Col0, only a small number are reversed in the abi4vtc2 double mutants relative to either abi4 or vtc2. We conclude that AA controls growth via an ABA and abi4-dependent signalling pathway. The vtc and abi4 mutants have enhanced glutathione levels and common redox signalling pathways leading to similar gene expression patterns.
The transcription factor ABI4 Is required for the ascorbic acid-dependent regulation of growth and regulation of jasmonate-dependent defense signaling pathways in Arabidopsis.
Age, Specimen part
View SamplesThe role of abscisic acid (ABA) signalling in the ascorbic acid (AA)-dependent control of plant growth and defence was determined using the vtc1 and vtc2 mutants, which have impaired ascorbic acid synthesis, and in the abi4 mutant that is impaired in ABA-signalling. ABA levels were increase in the mutants relative to the wild type (Col0). Like vtc1 the vtc2 mutants have a slow growth relative to Col0. However, the wild type phenotype is restored in the abi4vtc2 double mutant. Similarly, the sugar sensing phenotype of in the abi4 is reversed in the abi4vtc2 double mutant. The vtc1 and vtc2 leaf transcriptomes show up to 70 % homology with abi4. Of the transcripts that are altered in the mutants a relative to Col0, only a small number are reversed in the abi4vtc2 double mutants relative to either abi4 or vtc2. We conclude that AA controls growth via an ABA and abi4-dependent signalling pathway. The vtc and abi4 mutants have enhanced glutathione levels and common redox signalling pathways leading to similar gene expression patterns.
The transcription factor ABI4 Is required for the ascorbic acid-dependent regulation of growth and regulation of jasmonate-dependent defense signaling pathways in Arabidopsis.
Age, Specimen part
View SamplesAlterations of hydrogen peroxide (H2O2) levels have a profound impact on numerous signaling cascades orchestrating stress responses, plant growth and development, including programmed cell death. To expand the repertoire of known molecular mechanisms implicated in H2O2 signaling, we performed a forward chemical screen to identify small molecules that could alleviate the photorespiratory-induced cell death phenotype of Arabidopsis thaliana mutants lacking H2O2 scavenging capacity by peroxisomal CATALASE2. Here, we report the characterization of pakerine, a m-sulfamoyl benzamide from the sulfonamide family. Pakerine alleviates the cell death phenotype of cat2 mutants exposed to photorespiration-promoting conditions and delays dark-induced senescence in wild type Arabidopsis leaves. By using a combination of transcriptomics, metabolomics and affinity purification we identified ABNORMAL INFLORESCENCE MERISTEM 1 (AIM1) as a putative protein target of pakerine. AIM1 is a 3-hydroxyacyl-CoA dehydrogenase involved in β-fatty acid oxidation that contributes to jasmonic acid (JA) and salicylic acid (SA) biosynthesis. Whereas intact JA biosynthesis was not required for pakerine bioactivity, our results point towards a role for β-oxidation-dependent SA production in execution of H2O2-mediated cell death.
Chemical Genetics Approach Identifies Abnormal Inflorescence Meristem 1 as a Putative Target of a Novel Sulfonamide That Protects Catalase2-Deficient <i>Arabidopsis</i> against Photorespiratory Stress.
Specimen part
View SamplesThe severe acute respiratory syndrome (SARS) epidemic was characterized by increased pathogenicity in the elderly due to an early exacerbated innate host response. SARS-CoV is a zoonotic pathogen that entered the human population through an intermediate host like the palm civet. To prevent future introductions of zoonotic SARS-CoV strains and subsequent transmission into the human population, heterologous disease models are needed to test the efficacy of vaccines and therapeutics against both late human and zoonotic isolates. Here we show that both human and zoonotic SARS-CoV strains can infect cynomolgus macaques and resulted in radiological as well as histopathological changes similar to those seen in mild human cases. Viral replication was higher in animals infected with a late human phase isolate compared to a zoonotic isolate. Host responses to the three SARS-CoV strains were similar and only apparent early during infection with the majority of genes associated with interferon signalling pathways.This study characterizes critical disease models in the evaluation and licensure of therapeutic strategies against SARS-CoV for human use
Comparative pathogenesis of three human and zoonotic SARS-CoV strains in cynomolgus macaques.
Specimen part, Time
View SamplesCirculating cell-free RNA in the blood provides a potential window into the health, phenotype, and developmental programs of a variety of human organs. We used high-throughput methods of RNA analysis such as microarrays and next-generation sequencing to characterize the global landscape of circulating RNA in human subjects. By focusing on tissue-specific genes, we were able to identify the relative contributions of these tissues to circulating RNA and monitor changes during tissue development and neurodegenerative disease states.
Noninvasive in vivo monitoring of tissue-specific global gene expression in humans.
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