Project description:Transcriptome analysis of apoplastic reactive oxygen species (ROS) signaling and dissection of the roles of WRKY25, WRKY33 and WRKY75 in the transcriptional reprogramming triggered by apoplastic ROS
Project description:Ozone (O3) is a phytotoxic air pollutant that enters the plant through stomata and activates cell death programs leading to development of lesions in sensitive plant species. Exposure to O3 provokes the formation of reactive oxygen species (ROS) in the apoplast of plant cells. Imbalanced ROS homeostasis has deleterious toxic effects on DNA, proteins, lipids, and carbohydrates. However, ROS are not merely damaging molecules, as they also initiate signaling events that help plants acclimate to stress. Like under most abiotic and biotic stresses, apoplastic ROS signaling triggered by O3 induces massive changes in gene expression, enzyme activities and metabolic profiles. Thus, O3 is a very useful tool to study general mechanisms of ROS signaling and regulation of gene expression. Here we used a combination of transcriptome analysis and cell death assays to identify molecular mechanism initiated by apoplastic ROS signaling involved in the regulation of defense signaling and cell death in Arabidopsis thaliana.
Project description:We used the flu mutant of Arabidopsis and a transgenic line that overexpresses the thylakoid-bound ascorbate peroxidase (tAPX) to address the interactions between different reactive oxygen species (ROS) signaling pathways. The conditional flu mutant of Arabidopsis accumulates excess protochlorophyllide in the dark within chloroplast membranes that upon illumination acts as a photosensitizer and generates singlet oxygen (1O2). Immediately after the release of singlet oxygen rapid changes in nuclear gene expression occur. Distinct sets of genes were activated that were different from those induced by other reactive oxygen species, superoxide or hydrogen peroxide (H2O2), suggesting that different types of active oxygen species activate distinct signaling pathways. It was not known whether the pathways operate separately or interact with each other. We have addressed this problem by modulating noninvasively the level of H2O2 in plastids by means of a transgenic line that overexpresses the thylakoid-bound ascorbate peroxidase (tAPX, line 14/2 PMID: 15165186). In the flu mutant overexpressing tAPX, the expression of most of the nuclear genes that were rapidly activated after the release of 1O2 was significantly higher in flu plants overexpressing tAPX, whereas in wild-type plants, overexpression of tAPX had only a very minor impact on nuclear gene expression. The results suggest that H2O2 antagonizes the 1O2-mediated signaling of stress responses as seen in the flu mutant. This cross-talk between H2O2- and 1O2-dependent signaling pathways might contribute to the overall stability and robustness of wild-type plants exposed to adverse environmental stress conditions. Keywords: Single time point comparison
Project description:Transcriptome analysis of apoplastic reactive oxygen species signaling in Arabidopsis thaliana accessions with varying ozone sensitivity.
Project description:As sessile organism, plants evolved a highly complicated signaling system to cope with unfavorable and fluctuating environmental conditions. Rapid and transient Reactive Oxygen Species (ROS) burst is a common response to both biotic and abiotic stresses. Plants exposed with O3 could trigger extracellular similar ROS production through cell wall peroxidases and NPADPH oxidases, resulting in changes in the gene expression and cell death. Whereas ROS induced cell death is not simply due to its toxicity, rather due to interplay with several other signaling pathways, such as salicylic acid (SA), jasmonic acid (JA) and ethylene signaling pathways. Furthermore, the three hormones have both synergistic and antagonistic interactions, where the suppression of JA signaling by SA is the mostly studied. In addition, ethylene promotes cell death while JA has a protective role upon O3 exposure. The role of SA is more complicated; depending on the genetic background it can have either cell death promoting or protecting roles. Hence, a clean system to deliver apoplastic ROS is required to study the role of ROS apart from con-current activation of other signaling pathways. Arabidopsis thaliana offer a convenient system to study apoplastic ROS signaling due to the availability of hormone signaling or biosynthesis mutants including the JA receptor mutant coi1-16 (CORONATINE INSENSITIVE1), the essential ethylene signaling mutant ein2 (ETHYLENE INSENSITIVE2), the SA biosynthesis mutant sid2 (SALICYLIC ACID INDUCTION DEFICIENT2 also known as ISOCHORISMATE SYNTHASE1), and essential regulators in SA/JA/ethylene-induced defense response triple mutant tga2 tga5 tga6 (Clade II TGA transcription factors). Here we used a combination of transcriptome analysis, cell death assays and mutant analysis to systematically quantified the contribution of hormone signaling in relation to apoplastic ROS signaling, identified transcription factors (TFs) involved in ROS regulation and dissected the components involved in defense hormones associated cell death. Transcriptome profiling of ozone response using two arabidopsis triple mutants coi1-16 ein2 sid2 and tga2 tga5 tga6 related to Jasmonic acid, salicylic acid and ethylene signaling to identify hormone-independant apoplastic ROS signaling
Project description:Plants are exposed to regular diurnal rhythms of light and dark. Changes in the photoperiod by the prolongation of the light period cause photoperiod stress in short day-adapted Arabidopsis thaliana. Here we report on the transcriptional response to photoperiod stress of wild-type A. thaliana and photoperiod stress-sensitive cytokinin signaling and clock mutants. Transcriptomic changes induced by photoperiod stress included numerous changes in reactive oxygen species (ROS)-related transcripts and showed a strong overlap with alterations occurring in response to ozone stress and pathogen attack, which have in common the induction of an apoplastic oxidative burst. A core set of photoperiod stress-responsive genes has been identified, including salicylic acid (SA)-biosynthesis and -signaling genes. Genetic analysis revealed a central role for NPR1 in the photoperiod stress response as npr1-1 mutants were stress-insensitive. Photoperiod stress treatment led to a strong increase in camalexin levels which is also observed in response to pathogen infections. Photoperiod stress induced the resistance of Arabidopsis plants to a subsequent infection by Pseudomonas syringae pv. tomato DC3000 indicating priming of the defence response. Together, photoperiod stress causes transcriptional reprogramming resembling plant pathogen defence responses and induces systemic acquired resistance in the absence of a pathogen.
Project description:Transcriptome analysis of apoplastic reactive oxygen species signalling in Arabidopsis thaliana accessions with varying ozone sensitivity.
Project description:We used microarrays to detail Arabidopsis gene expression in response to paraquat, a herbicide that acts as a terminal oxidant of photosystem I that in the light leads to the enhanced generation of superoxide and hydrogen peroxide inside plastids. Within a few hours after paraquat treatment changes in nuclear gene expression occur. Distinct sets of genes were activated that were different from those induced by another reactive oxygen species, singlet oxygen. Keywords: Time course