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Mitochondrial dysfunction in Arabidopsis thaliana.

ABSTRACT: We characterized the global response of plants carrying a mitochondrial dysfunction induced by the expression of the unedited form of the ATP synthase 9 subunit. The u-ATP9 transgene driven by A9 and Apetala3 promoters induce mitochondrial dysfunction revealed by a decrease in both oxygen uptake and ATP levels, with an increase in ROS and a concomitant oxidative stress response. The transcriptome analysis of young Arabidopsis flowers, validated by RT-PCR and enzymatic or functional tests, show dramatic changes in u-ATP9 plants. Both lines present a modification in the expression of several genes involved in carbon, lipid and cell wall metabolism, suggesting that an important metabolic readjustment occurs in plants with a mitochondrial dysfunction. Interestingly, transcript levels involved in mitochondrial biogenesis, protein synthesis, and degradation are affected. Moreover, several mRNA levels for transcription factors and DNA binding proteins were also changed. Some of them are involved in stress and hormone response, suggesting that several signaling pathways overlap. Indeed, the transcriptome data reveal that the mitochondrial dysfunction dramatically alters genes involved in signaling pathways, including those involved in ethylene, absicic acid and auxin signal transduction. Our data suggest that the mitochondrial dysfunction model used in this rapport may be useful to uncover the retrograde signaling mechanism between the nucleus and mitochondria in plant cells.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE14240 | GEO | 2009/02/15

SECONDARY ACCESSION(S): PRJNA111163

REPOSITORIES: GEO

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Project description:We characterized the global response of plants carrying a mitochondrial dysfunction induced by the expression of the unedited form of the ATP synthase 9 subunit. The u-ATP9 transgene driven by A9 and Apetala3 promoters induce mitochondrial dysfunction revealed by a decrease in both oxygen uptake and ATP levels, with an increase in ROS and a concomitant oxidative stress response. The transcriptome analysis of young Arabidopsis flowers, validated by RT-PCR and enzymatic or functional tests, show dramatic changes in u-ATP9 plants. Both lines present a modification in the expression of several genes involved in carbon, lipid and cell wall metabolism, suggesting that an important metabolic readjustment occurs in plants with a mitochondrial dysfunction. Interestingly, transcript levels involved in mitochondrial biogenesis, protein synthesis, and degradation are affected. Moreover, several mRNA levels for transcription factors and DNA binding proteins were also changed. Some of them are involved in stress and hormone response, suggesting that several signaling pathways overlap. Indeed, the transcriptome data reveal that the mitochondrial dysfunction dramatically alters genes involved in signaling pathways, including those involved in ethylene, absicic acid and auxin signal transduction. Our data suggest that the mitochondrial dysfunction model used in this rapport may be useful to uncover the retrograde signaling mechanism between the nucleus and mitochondria in plant cells. Arabidopsis oligonucleotide microarrays fabricated by the University of Arizona contain 26,000 oligonucleotides (http://www.ag.arizona.edu/microarray/). RNA was isolated from 6-week-old flowers from u-ATP9 and wt plants. The experimental (mutant) and reference (wild type) RNA samples were reverse-transcribed and directly labeled with either Cy5-dUTP or Cy3-dUTP fluorescent dye (GE Healthcare), using random hexamer primers (Invitrogen). Excess nucleotides and primers were removed using QIAquick PCR Purification Kit (Qiagen). Labeled samples were mixed and then hybridized to microarray for 15 h at 60°C. The slides were washed at room temperature in three wash steps: 2 x SSC, 0.5% SDS; 0.5 x SSC; and 0.05 x SSC for 5 min each with gentle shaking. The slides were scanned with a GenePix 4000B Scanner (Axon Instruments Inc., Union City, CA). Normalization between the Cy3 and Cy5 fluorescent dye emission channels was achieved by adjusting the levels of both image intensities. The experiments were repeated four times with samples from different experiments, as biological replicates. In dye swapping experiments, the RNA samples from different experiments were reciprocally labeled, both as a biological and technical repetition for comparing the reproducibility of the experiments. Hybridization intensities for each microarray element were measured using ScanAlyze 4.24 (available at http://genome-www4.stanford.edu/MicroArray/SMD/restech.html). The two channels were normalized in log space using the z-score normalization on a 95% trimmed data set. We removed unreliable spots according to the following criteria: spots flagged as having false intensity caused by dust or background on the array were removed; and spots for which intensity was less than three fold above background were also eliminated. Data from multiple experiments were normalized (Bolstad, 2003) and signals from spots from different experiments were statistically analyzed using Significance Analysis of Microarrays using the one class response (SAM, http://www-stat.stanford.edu/~tibs/SAM/), cut at a false discovery rate < 10% (Tusher, 2001).

Project description:The mitochondrial and nuclear genomes contribute to mitochondrial function, and when mitochondrial function is compromised, mitochondrial retrograde signaling alters nuclear gene expression. We performed gene expression profiling of engineered cells that had mitochondria containing a disease-associated mutation that causes mitochondrial dysfunction. By generating networks of transcription factors that targeted these genes, the authors revealed putative mitochondrial retrograde signaling pathways. One such pathway involved retinoic acid receptor alpha (RXRA), the mRNA for which was reduced in the mutant cells. Network analysis and experiments in cells suggested that mitochondrial dysfunction caused by the mutation initiated a positive feedback loop that aggravated mitochondrial dysfunction: Reduced RXRA abundance further compromised expression of genes encoding products involved in mitochondrial function and translation. This gene-transcription factor mapping-network approach may reveal targets for therapeutic intervention of diseases associated with mitochondrial dysfunction. To investigate retrograde signaling pathways induced by the mitochondrial dysfunction caused by the mt3243 mutation, we generated the three types of cybrid cells using a mitochondria-mediated transformation method. Cells lacking mtDNA (rho0) were fused with mtDNAs with the mt3243 mutation isolated from platelets of a diabetic patient with sensorineural hearing loss. We then isolated three types of cybrid cells: W cells had wild-type mtDNA (3243A homoplasmy), H cells had both the mutant and wild-type mtDNA (3243A/G heteroplasmy) with 70% of the mtDNA containing 3243G, and M cells with only mutant mtDNA (3243G homoplasmy). Gene expression profiles of cybrid cells were generated using Illumina HumanHT-12-v3-BeadChip (Illumina, San Diego, CA), which includes 49,896 probes corresponding to 25,202 annotated genes. According to the Illumina protocols, three biological triplicates of each type of cybrid cells were analyzed. Total RNA (500ng) was isolated from cybrid cells using RNeasy Mini Kit (Qiagen, GmbH, Germany). RNA integrity number (RIN) was in the range of RIN = 9.2 and 10 when measured with an Agilent 2100 Bioanalyzer. RNA was reversely transcribed and amplified using IlluminaTotalPrep RNA amplification kit (Ambion, Austin, TX). In vitro transcription was then carried out to prepare cRNA. The cRNAs were hybridized to the array and then labeled with Cy3-streptavidin (Amersham Bioscience, Little Chalfont, UK). The fluorescent signal on the array was measured with a BeadStation 500 System (Illumina, San Diego, CA).

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Mitochondrial dysfunction in Arabidopsis thaliana.

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