Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of Arabidopsis wild type and TROL (AT4G01050) knock-out plants

ABSTRACT: Here we describe TROL (thylakoid rhodanese-like protein), a nuclear-encoded component of thylakoid membranes that is required for sustaining efficient linear electron flow in vascular plants. Thus, TROL might represent a missing thylakoid membrane linker for the assembly of a ternary complex between FNR, ferredoxin and NADP+. Such a complex is necessary for maintaining photosynthetic redox poise and balancing between several alternative electron-transport pathways of oxygenic photosynthesis. TROL inactivation modulates the expression of 638 nuclear genes, revealing a novel retrograde signaling pathway. Chloroplasts are the major source of NADPH which is exported to the cytosol where it participates in various redox-dependent processes. TROL is most likely the first element in a metabolic signaling pathway which influences the expression of a large set of stress related genes. Among them are O-methyltransferases and anthocyanin 5-aromatic acyltransferase which are highly upregulated. Microarray analysis was performed in order to identify metabolic networks and pathways regulated by the deficient protein TROL. Comparing ATH1 Affymetrix data results, 317 genes were down-regulated and 321 genes were classified as up-regulated, amongst which mostly affected enzymes were catalyses, oxigenases, monooxygenases and reductases involved in the process of photosynthesis.

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Ana Tomasic

PROVIDER: E-MEXP-1783 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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. Experiment Overall Design: Arabidopsis thaliana rosette leaves were harvested after 2 h of reillumination following a 8h dark period for RNA extraction and hybridization on Affymetrix ATH1 microarrays. The entire experiment was performed six times, providing independent biological replicates. For each of the six experiments, all four lines, wild-type, thylakoidal ascorbate peroxidase overexpressor (over tAPX, line 14/2), flu mutant and flu plants overexpressing thylakoidal ascorbate peroxidase were grown for 3 weeks under continuous light at 90 mmol. m-2 . s-1, transferred to the dark for 8 h, and reilluminated for 120 min before the rosette leaves of at least 10 plants per line were harvested. Total RNAs from three separate biological experiments were pooled (= 1 biological rep.) for the preparation of cDNA and the subsequent synthesis of biotin-labeled complementary RNA as recommended by Affymetrix.

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Transcription profiling of Arabidopsis wild type and TROL (AT4G01050) knock-out plants

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