SUPPRESSOR OF GAMMA RESPONSE1 Links DNA Damage Response to Organ Regeneration.

In Arabidopsis, DNA damage-induced programmed cell death is limited to the meristematic stem cell niche and its early descendants. The significance of this cell-type-specific programmed cell death is unclear. Here, we demonstrate in roots that it is the programmed destruction of the mitotically compromised stem cell niche that triggers its regeneration, enabling growth recovery. In contrast to wild-type plants, plants, which are defective in damage-induced programmed cell death, maintain the cell identities and stereotypical structure of the stem cell niche after irradiation, but these cells fail to undergo cell division, terminating root growth. We propose DNA damage-induced programmed cell death is employed by plants as a developmental response, contrasting with its role as an anticarcinogenic response in animals. This role in plants may have evolved to restore the growth of embryos after the accumulation of DNA damage in seeds.