Differences in RAD51 transcriptional response and cell cycle dynamics reveal varying sensitivity to DNA damage among Arabidopsis thaliana root cell types

SUMMARY Throughout their lifecycle, plants are subjected to DNA damage from various sources, both environmental and endogenous. Investigating the mechanisms of the DNA damage response (DDR) is essential to unravel how plants adjust to the changing environment that can elicit varying amounts of DNA damage. Using a combination of state-of-the-art cell biology methods including whole-mount single-molecule RNA fluorescence in situ hybridization (WM-smFISH), allowing detection of individual mRNA molecules in intact plant tissue and plant cell cycle reporter lines we investigated how the transcriptional activation of a key homologous recombination (HR) gene, RAD51, occurs in response to increasing amounts of DNA damage in Arabidopsis thaliana roots. The results uncover consistent variations in RAD51 transcriptional response and cell cycle arrest among distinct cell types and developmental zones. Furthermore, we demonstrate that DNA damage induced by genotoxic stress results in RAD51 transcription throughout the whole cell cycle, dissociating its traditional link with S/G2 phases. This work advances the current comprehension of DNA damage response in plants showing quantitative differences in DDR activation. In addition, it reveals new associations with the cell cycle and cell types, providing crucial insights for further studies of the broader response mechanisms in plants. Competing Interest Statement The authors have declared no competing interest.