BACKGROUND: Plants have evolved a unique epigenetic process to target DNA @entity5538 methylation: RNA-directed DNA methylation (RdDM). During RdDM, small RNAs (smRNAs) guide methylation of homologous DNA loci. In @entity958 , the de novo DNA methyltransferase that ultimately methylates cytosines guided by smRNAs in all sequence contexts is @entity68283 ( @entity68283 ). Recent reports have shown that @entity68283 requires the catalytic mutated paralog DRM3 to exert its function through a still largely unknown process. To shed light on how DRM3 affects RdDM, we have further characterized its role at the molecular and cytological levels. FINDINGS: Although DRM3 is not required for RdDM loci transcriptional silencing, it specifically affects loci's DNA methylation. Interestingly, DRM3 and @entity68283 regulate the DNA methylation in a subset of loci differently.Fluorescence In Situ Hybridization and immunolocalization analyses showed that DRM3 is not required for the large-scale nuclear organization of heterochromatin during interphase, with the notable exception of the 45S ribosomal RNA loci. DRM3 localizes exclusively to the nucleus and is enriched in a round-shaped domain located in the nucleolar periphery, in which it colocalizes with components of the RdDM pathway. CONCLUSIONS: Our analyses reinforce the previously proposed chaperone role of DRM3 in RdDM. Overall, our work further demonstrates that DRM3 most likely functions exclusively with @entity68283 in RdDM and not with other A. thaliana DNA methyltransferases. However, DRM3's regulation of DNA methylation is likely target- or chromatin context-dependent. DRM3 hypothetically acts in RdDM either upstream of @entity68283 , or in a parallel step.

The cytological and molecular role of DOMAINS REARRANGED METHYLTRANSFERASE3 in RNA-dependent DNA methylation of XXXX .

@entity958 :: ('3702', 'Species') :: ['Arabidopsis thaliana'] @entity68283 :: ('831315(Tax:3702)', 'Gene') :: ['DRM2', 'DOMAINS REARRANGED METHYLTRANSFERASE 2'] @entity5538 :: ('MESH:D003596', 'Chemical') :: ['cytosine']
@entity958 :: (3702,Species) :: ['Arabidopsis thaliana']
