Abstract
As a sessile organism, plants are constantly challenged by diverse environmental stresses that threaten genome integrity by way of induction of DNA damage. In plants, each tissue is composed of differentiated cell types, and the response to DNA damage differs among each cell type. However, limited information is available on the subnuclear dynamics of different cell types in response to DNA damage in plants. A chromatin remodeling factor RAD54, which plays an important role in the exchange reaction and alteration of chromatin structure during homologous recombination, specifically accumulates at damaged sites, forming DNA repair foci (termed RAD54 foci) in nuclei after γ-irradiation. In this study, we performed a time-course analysis of the appearance of RAD54 foci in root cells of Arabidopsis after γ-irradiation to characterize the subnuclear dynamics in each cell type. A short time after γ-irradiation, no significant difference in detection frequency of RAD54 foci was observed among epidermal, cortical, and endodermal cells in the meristematic zone of roots. Interestingly, cells showing RAD54 foci persisted in roots at long time after γ-irradiation, and RAD54 foci in these cells localized to nuclear periphery with high frequency. These observations suggest that the nuclear envelope plays a role in the maintenance of genome stability in response to DNA damage in Arabidopsis roots.
Highlights
Genome integrity is constantly threatened by exogenous and endogenous stresses that induce DNA damage in organisms
To investigate the DNA repair activity in each cell type in response to DNA damage, we observed the formation of RAD54 foci in root cells after γ-irradiation, which induces double-strand breaks (DSBs) in DNA
RAD54 foci are subnuclear foci where homologous recombination (HR) repair might occur in chromatin, RAD54 foci can be used to monitor the activity of HR repair in living cells (Hirakawa et al, 2017)
Summary
Genome integrity is constantly threatened by exogenous (e.g., ionizing radiation, ultraviolet light, and chemical components) and endogenous stresses (e.g., stalled DNA replication forks and reactive oxygen species) that induce DNA damage in organisms. DNA damage is caused by diverse environmental stresses, such as stress-mediated reactive oxygen species, pathogen infection, high boron concentration, and aluminum ions (Rounds and Larsen, 2008; Sakamoto et al, 2011; Baxter et al, 2014; Song and Bent, 2014). Signaling of DNA damage is rapidly coordinated with several mediators to maintain genome stability in plants. The active form of SOG1 directly regulates expression of genes participating in DNA repair, cell cycle progression, pathogen response, and phytohormone signaling (Ogita et al, 2018).
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