Abstract
Chromatin accessibility is closely associated with chromatin functions such as gene expression, DNA replication, and maintenance of DNA integrity. However, the relationship between chromatin accessibility and plant hormone signaling has remained elusive. Here, based on the correlation between chromatin accessibility and DNA damage, we used the sensitivity to DNA double strand breaks (DSBs) as an indicator of chromatin accessibility and demonstrated that auxin regulates chromatin accessibility through the TIR1/AFBs signaling pathway in proliferative cells. Treatment of proliferating plant cells with an inhibitor of the TIR1/AFBs auxin signaling pathway, PEO-IAA, caused chromatin loosening, indicating that auxin signaling functions to decrease chromatin accessibility. In addition, a transcriptome analysis revealed that several histone H4 genes and a histone chaperone gene, FAS1, are positively regulated through the TIR1/AFBs signaling pathway, suggesting that auxin plays a role in promoting nucleosome assembly. Analysis of the fas1 mutant of Arabidopsis thaliana confirmed that FAS1 is required for the auxin-dependent decrease in chromatin accessibility. These results suggest that the positive regulation of chromatin-related genes mediated by the TIR1/AFBs auxin signaling pathway enhances nucleosome assembly, resulting in decreased chromatin accessibility in proliferative cells.
Highlights
Chromatin functions depend on the accessibility of chromatin-interacting factors and chromatin affecters
We considered the change in the level of damaged DNA to represent the change in chromatin accessibility in this study
We found that the sensitivity of root elongations to 2.5 and 5 μM zeocin was increased by the PEO-indole acetic acid (IAA) treatment (Fig. 5A, Supplementary Fig. S3), confirming that the increase in chromatin accessibility strengthens the sensitivity to double strand breaks (DSBs)
Summary
Chromatin functions depend on the accessibility of chromatin-interacting factors and chromatin affecters. Access of DNA-damaging factors including reactive oxygen species (ROS) and chemicals must be restricted to prevent DNA damage[2,3]. In Arabidopsis thaliana, the recruitment of SWI2/SNF2 chromatin remodeling ATPases to chromatin by the MONOPTEROS transcription factor increases the accessibility of additional transcription factors to DNA to initiate the transcription of genes involved in flower primordium development under high-auxin conditions[15]. The expression of the histone H4 gene decreased under auxin-starvation conditions in cultured tobacco BY-2 cells[23], and increased in response to an auxin treatment in hot pepper[22]. Our results demonstrate that auxin reduces chromatin accessibility through the TIR1/AFB pathway in proliferative cells
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