Condensin II mediates efficient chromatid resolution and resistance to genotoxic stress in Arabidopsis

Genome functions are regulated by the means of chromatin and 3D chromosome organization. Dynamic condensation and relaxation of chromosomes during cell cycle is largely controlled by the Condensin complexes. We mapped mutants in Condensin II subunits SMC2A, CAP-D3 and CAP-H2 as hypersensitive to DNA-protein crosslink (DPC) inducer zebularine. This suggested that Condensin II complex is required for resistance to genotoxic stress in Arabidopsis and prompted us to explore the underlying phenotypes. We show that the Condensin II role in resistance to zebularine is independent of the DNA damage response signaling by SOG1 and the homology-directed repair pathway. Furthermore, we found that Arabidopsis Condensin II mutants have incompletely condensed mitotic chromosomes and show abnormal chromatin connections during anaphase. Based on the structural and temporal analyses, we propose that the connections represent catenated chromatids. The chromosome connections were more frequent when the Condensin II mutants were treated by zebularine or TOP2 crosslinker and inhibitor ICRF-187. Altogether, we demonstrate that the proper large-scale chromatin organization by Condensin II is important for resistance to DNA damage response-inducing agents in Arabidopsis.