Tissue-specific regulation of cell-cycle responses to DNA damage in Arabidopsis seedlings.

DNA damage-induced cell-cycle "checkpoint" responses reduce the mutagenic effects of this damage. However, the maintenance of genomic stability comes at a price: the slowing of growth and a delay in the development of critical tissues. In mammals, every mutated cell has the potential to become cancerous and therefore lethal. In plants, the risk of lethal cancers is essentially nil and the costs of delays in development are very high. Here, we investigate DNA damage checkpoint responses in meristematic (root and shoot tip) versus strictly somatic (stomatal and endoreduplicating) tissues in plants. We find that the ionizing radiation (IR)-induced cell-cycle responses observed in the root and shoot tip meristems do not apply to more differentiated tissues.