The cyclin‐dependent kinase inhibitor KIP‐RELATED PROTEIN 6 promotes stem cell death upon DNA damage in Arabidopsis roots

Maintenance of genome integrity is essential for plant growth and survival. Plants have evolved specialised DNA damage responses that coordinate DNA repair, cell cycle arrest and stem cell-specific cell death. However, the mechanism through which damaged stem cells are selectively eliminated remains unclear. Here, we show that the cyclin-dependent kinase inhibitor KIP-RELATED PROTEIN 6 (KRP6) is induced in Arabidopsis thaliana in response to DNA damage. Reporter analyses reveal that KRP6 induction occurs in the root stem cell niche under genotoxic stress. We further demonstrate that the NAC-type transcription factor, SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1), a central regulator of the plant DNA damage response, directly activates KRP6 expression upon DNA damage. Loss-of-function krp6 mutant exhibits reduced stem cell death after DNA damage, whereas KRP6 overexpression enhances cell death. The expression of a dominant-negative CDKA;1 allele in vascular stem cells promotes DNA damage-induced stem cell death. Together, these findings identify KRP6 as a key regulator linking genotoxic stress to stem cell death, highlighting the important role of CDK inhibition in safeguarding genome integrity in plants.