Abstract
Although researchers have established that DNA methylation and active demethylation are dynamically regulated in plant cells, the molecular mechanism for the regulation of active DNA demethylation is not well understood. By using an Arabidopsis (Arabidopsis thaliana) line expressing the Promoter RESPONSIVE TO DEHYDRATION 29A:LUCIFERASE (ProRD29A:LUC) and Promoter cauliflower mosaic virus 35S:NEOMYCIN PHOSPHOTRANSFERASE II (Pro35S:NPTII) transgenes, we isolated an mbd7 (for methyl-CpG-binding domain protein7) mutant. The mbd7 mutation causes an inactivation of the Pro35S:NPTII transgene but does not affect the expression of the ProRD29A:LUC transgene. The silencing of the Pro35S:NPTII reporter gene is associated with DNA hypermethylation of the reporter gene. MBD7 interacts physically with REPRESSOR OF SILENCING5/INCREASED DNA METHYLATION2, a protein in the small heat shock protein family. MBD7 prefers to target the genomic loci with high densities of DNA methylation around chromocenters. The Gypsy-type long terminal repeat retrotransposons mainly distributed around chromocenters are most affected by mbd7 in all transposons. Our results suggest that MBD7 is required for active DNA demethylation and antisilencing of the genomic loci with high densities of DNA methylation in Arabidopsis.
Highlights
Researchers have established that DNA methylation and active demethylation are dynamically regulated in plant cells, the molecular mechanism for the regulation of active DNA demethylation is not well understood
Because ROS4/INCREASED DNA METHYLATION1 (IDM1) interacts with ROS5/IDM2, and because REPRESSOR OF SILENCING1 (ROS1) is likely in the complex of ROS5/IDM1 (Zhao et al, 2014), these results suggest that ROS1, ROS4/IDM1, ROS5/ IDM2, and MBD7 form a protein complex in the nucleus
Previous studies suggest that ROS4/ IDM1 interacts with ROS5/IDM2, which regulates H3K18 acetylation, and creates a favorable chromatin environment for recruiting of ROS1 (Li et al, 2012; Qian et al, 2012, 2014; Zhao et al, 2014)
Summary
Researchers have established that DNA methylation and active demethylation are dynamically regulated in plant cells, the molecular mechanism for the regulation of active DNA demethylation is not well understood. By using an Arabidopsis (Arabidopsis thaliana) line expressing the Promoter RESPONSIVE TO DEHYDRATION 29A:LUCIFERASE (ProRD29A:LUC) and Promoter cauliflower mosaic virus 35S:NEOMYCIN PHOSPHOTRANSFERASE II (Pro35S:NPTII) transgenes, we isolated an mbd (for methyl-CpG-binding domain protein7) mutant. 35S-SUC2 transgene or a chop PCR marker for assaying DNA methylation at the 39 region of At1g26400 from transfer DNA (T-DNA) insertion mutants, researchers recently identified two genes involved in active DNA demethylation: ROS4/INCREASED DNA METHYLATION1 (IDM1) and ROS5/IDM2 (Li et al, 2012; Qian et al, 2012, 2014; Zhao et al, 2014). We found that MBD7 interacts physically with ROS5/IDM2 and is required for the active DNA demethylation of certain genomic loci, especially for the Gypsy-type long terminal repeat (LTR) retrotransposons with high densities of DNA methylation around chromocenters in Arabidopsis
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