IBM1, a JmjC domain histone demethylase, is involved in the regulation of RNA-directed DNA methylation through epigenetic control of RDR2 and DCL3 expression in Arabidopsis.

The small RNA mediated DNA methylation (RdDM) is highly elaborated in Arabidopsis as an important epigenetic pathway controls expression of genes and multiple developmental processes. RDR2 and DCL3 are necessary factors to the 24-nt siRNA biogenesis and the RdDM pathway. Here, we find that IBM1 (increase in BONSAI methylation 1), a conserved JmjC family histone demethylase, could directly associated with the chromatin of RDR2 and DCL3. The IBM1 mutation induces hypermethylation on both H3K9 and DNA non-CG sites in these loci, and further represses their expression. The reduction of RDR2 and DCL3 may affect siRNA biogenesis in a locus-specific manner and disrupt the RdDM directed repression. It suggests an indirect way to regulate targets by IBM1 through control of siRNA biogenesis, and demonstrate the relationship between histone methylation and small RNAs. Genome-wide integrated mapping of mRNA transcripts and small RNAs, using whole plant of 10-days seedlings of the Columbia-0 wildtype and ibm1-3 mutant Arabidopsis thaliana.