A forward genetic screen to identify genes involved in the maintenance of organelle genome stability in Arabidopsis thaliana.

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Genetic instability is well known to induce many human pathologies such as cancer and neurodegenerative diseases. In plants, mutations can also destabilize genomes and, when occurring in organellar genomes (chloroplast and mitochondria) lead to phenotypic variations such as cytoplasmic male sterility (plant unable to shed pollen), variegation (plant with white and green leaves) and resistance to heat. Although these phenotypes may provide new, important agricultural traits, the mechanisms generating the related mutations remain elusive. Here we propose to evaluate the role of the genes involved in the maintenance of genetic stability in the organelles of Arabidopsis thaliana, the model organism for plant genetics studies. This will be achieved using a collection of more than 50,000 plants, each of them depleted for a particular gene. The methodology applied in this study will be to sow the plants on a growth medium containing a mutagenic agent to stimulate DNA instability in plants organelle. We hypothesize that plants depleted of a gene implicated in the maintenance of genetic stability will be more sensitive to such treatment. Afterwards, it will be possible to classify the genes identified in the different DNA metabolism pathways of plant organelle such as DNA replication and repair. Our work has already identified several genes involved in these pathways and further characterisation is underway. As a subsequent step in our study, it will be interesting to confirm whether the genes identified in Arabidopsis play a similar role in crops. Indeed, there is great agricultural interest to facilitate the production of mutant traits such as cytoplasmic male sterility (used for hybrid production), resistance to heat and variegation in crop plants.