DDM1 represses noncoding RNA expression and RNA-directed DNA methylation in heterochromatin

In this work, we studied function of rice DDM1 in coordinating DNA methylation, expression of small (sRNA) and long noncoding (lncRNA) RNAs, and nucleosome positioning by high throughput approaches.We show that the ddm1a/1b mutation resulted in ectopic CHH methylation of transposable elements (TE) and repeats. The ectopicCHH methylationwas dependent on DRM2, a DNA methyltransferase involved in sRNA-dependent DNA-methylation (RdDM). The ddm1a/1b mutation resulted in increases of heterochromatic sRNA but decreases of euchromatic sRNA production,induced expression of a set of developmentally regulated heterochromatic lncRNA , and increased nucleosome occupancy of TE-related or silent genes including heterochromatic lncRNA loci. In particular,DDM1-mediated repression ofCentromericRetrotransposons of Rice1 (CRR1) was essential for centromere function. BS-seq of ddm1a/1b/drm2 triple mutant; two replicates for smRNA-seq of wt and ddm1a/1b double mutant.