Condensin II mediates resistance to genotoxic stress and prevents mitotic defects in Arabidopsis

Genome functions are regulated by chromatin and 3D chromosome organization. Dynamic condensation and relaxation of chromosomes during the cell cycle are largely controlled by the Condensin complexes. We mapped mutants in the Condensin II subunits SMC2A, CAP-D3 and CAP-H2 as hypersensitive to DNA-protein crosslink (DPC) inducers zebularine and ICRF-187. This suggested that Condensin II is required for resistance to genotoxic stress in Arabidopsis (Arabidopsis thaliana) and prompted us to explore the underlying phenotypes. We show that the role of Condensin II in resistance to zebularine is independent of DNA damage response signaling by SOG1 and homology-directed repair. Furthermore, we found that Arabidopsis Condensin II mutants have incompletely condensed mitotic chromosomes and show anaphase bridges. The anaphase bridges were more frequent upon treatment with zebularine or ICRF-187 and the duration of mitosis was prolonged. Altogether, we demonstrate that proper large-scale chromatin organization by Condensin II is important for resistance to DNA damage in Arabidopsis.