BrPARP1, Poly-ADP ribose polymerase, is specifically activated by BrSOG1 in response to DNA damage repair

Poly ADP-ribose polymerase 1 (PARP1), a highly conserved multifunctional enzyme, has been extensively characterized in animal systems, where it plays crucial roles in transcriptional regulation, the maintenance of cellular homeostasis, and DNA damage signaling and repair pathways. Nevertheless, within plant systems, the molecular mechanisms by which PARP1 mediates the DNA damage response(DDR) are still not fully elucidated. In this study, we systematically investigated the function of BrPARP1 in Brassica rapa (B. rapa) root development through comprehensive genetic and molecular analyses. Intriguingly, BrPARP1 overexpression (OE) inhibits meristematic tissue proliferation in root tips through negative regulation of cell cycle progression. Under DNA damage conditions, BrPARP1-OE lines exhibited excessive NAD+ depletion, leading to an energy crisis-induced cell death. Conversely, RNA interference (RNAi)-mediated suppression of BrPARP1 expression resulted in phenotypically opposite effects. Furthermore, BrPARP1 is transcriptionally regulated by BrSOG1, which binds to the BrPARP1 promoter motif (CTTTCAAGAGAAG). These findings establish a regulatory mechanism in which BrSOG1 modulates cellular energy homeostasis and apoptosis by transcriptional control of BrPARP1 expression. Transcriptomic analyses demonstrated that BrPARP1 participates in multiple DNA damage repair pathways, including non-homologous end joining (NHEJ), homologous recombination (HR), base excision repair (BER), and nucleotide excision repair (NER). This provides a novel hypothesis for the study of BrPARP1-mediated response to DNA damage and offers a new genetic target for enhancing stress resistance in B. rapa varieties.