Mitochondrial DNA Damage Response – MIT2DR

Plants and their photosynthetic capacity are essential for animal survival, as are the complementary activities of respiration that occur in mitochondria, which directly affect crop productivity and plant adaptation to environmental changes. Research on plant organellar biogenesis is therefore of major strategic importance. Mitochondria function depends on the maintenance and expression of its genome, the mtDNA, as well as on the tight coordination with the nuclear genome that is essential for energy homeostasis, plant fitness and response to stresses. All genomes are exposed to environmental and metabolic stresses that compromise their integrity, and cells have evolved surveillance checkpoints to coordinate cell-cycle progression with DNA repair, thereby ensuring faithful transmission of their genomes. While these mechanisms are well known for the nuclear DNA, the mitochondrial genetic compartment has received little attention. This is a major gap of knowledge because organelles, as the cell’s powerplant, are major sources of potentially DNA damaging molecules such as reactive oxygen species (ROS), and their genomes are thus particularly prone to accumulate lesions.
The "Mitochondrial DNA Damage Response" (MIT2DR) project aims to fill this gap. MIT2DR is grounded on key results jointly obtained by P1 & P2, showing that growth defects observed in mtDNA maintenance mutants correlated with the induction of cell cycle inhibitors apparently in response to a burst in ROS. Exploiting Arabidopsis mutants deficient in mtDNA repair and targeted mtDNA editing by TALEN nucleases, the project proposes to dissect the retrograde (mitochondria-to-nucleus) signaling cascades regulating the cellular response to mitochondrial DNA damage and thus to decipher how mtDNA damage impinges on plant development. The project will combine state-of-the-art genomic, genetic, biochemical and cytology approaches, and will explore cellular and transcriptional responses through transcriptome analysis, to identify changes in nuclear gene expression caused by mtDNA damage, and epigenome profiling, to reveal chromatin changes associated to transcriptome reprogramming. Early responses will be studied using inducible TALEN exonucleases. To dissect the mtDNA-damage signaling cascade we will investigate ROS production and detoxification in TALEN plants and mtDNA repair mutants, using plant reporter lines expressing fluorescent biosensors. Finally, the MIT2DR project will identify for new signaling elements through an unbiased genetic screen approach.
The project capitalizes in the complementary expertise of the two partners: Partner P1 is an old hand on gene expression in plant mitochondria and a major contributor in the field of plant mtDNA recombination and repair, while Partner P2 has extensive experience in cell cycle regulation, analysis of cell cycle progression using cytology and live imaging approaches, and analysis of DNA methylation and chromatin landscapes by ChIP-seq.