MORC and MOM1 spatially constrain RNA Polymerase V chromatin positioning to shape DNA methylation landscapes

Plant-specific RNA Polymerase V (Pol V) transcribes noncoding RNAs in the RNA-directed DNA methylation pathway, thereby influencing gene expression and genome stability by controlling de novo DNA methylation. However, the mechanisms governing precise chromatin localization and transcriptional activities of Pol V remain elusive. Here we show that Pol V localization is spatially constrained by the chromatin regulators microrchidia (MORC) and MORPHEUS' MOLECULE 1 (MOM1). MORC and MOM1 promote Pol V occupancy at sites near active chromatin, whereas their loss leads to redistribution of Pol V into CMT3-enriched heterochromatin, accompanied by noncoding RNA transcription, small RNA production and DNA methylation. Our findings reveal a combinatorial model in which recruitment, spatial constraint and DNA methylation feedback collectively define Pol V chromatin distribution and epigenetic function.