Abstract
Chromatin dynamics and arrangement are involved in many biological processes in nuclei of eukaryotes including plants. Plants have to respond rapidly to various environmental stimuli to achieve growth and development because they cannot move. It is assumed that the alteration of chromatin dynamics and arrangement support the response to these stimuli; however, there is little information in plants. In this study, we investigated the chromatin dynamics and arrangement with DNA damage in Arabidopsis thaliana by live-cell imaging with the lacO/LacI-EGFP system and simulation analysis. It was revealed that homologous loci kept a constant distance in nuclei of A. thaliana roots in general growth. We also found that DNA double-strand breaks (DSBs) induce the approach of the homologous loci with γ-irradiation. Furthermore, AtRAD54, which performs an important role in the homologous recombination repair pathway, was involved in the pairing of homologous loci with γ-irradiation. These results suggest that homologous loci approach each other to repair DSBs, and AtRAD54 mediates these phenomena.
Highlights
Dynamics support the response to DNA damage; little is known in plants
Our results suggest that the transient reduction in inter-allelic distance and increase in pairing frequency of homologous loci after double-strand breaks (DSBs) result in partial chromatin reorganisation of interphase nuclei and that AtRAD54 contributes to the subcellular movement of homologous loci in the homologous recombination (HR) repair pathway
Homologous loci are dispersed by condensin II, which is a protein complex that contributes to chromosome condensation and segregation during mitosis, in D. melanogaster[25]
Summary
We examined chromatin dynamics and arrangement in living roots of A. thaliana with DNA damage, focusing our attention on the distance between homologous loci using the lacO/LacI-EGFP system. We revealed that the homologous loci kept a constant three-dimensional distance in the nucleus using live-cell imaging with a bacterial operator/repressor system. The distance between two homologous loci in the interphase nucleus was shortened by γ -irradiation, which induces DNA double-strand breaks (DSBs). We found that AtRAD54, which performs an important role in the homologous recombination (HR) repair pathway, was involved in the approach of two homologous loci under γ -irradiation. Our results suggest that the transient reduction in inter-allelic distance and increase in pairing frequency of homologous loci after DSB result in partial chromatin reorganisation of interphase nuclei and that AtRAD54 contributes to the subcellular movement of homologous loci in the HR repair pathway
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