Forms a complex with FDM1/IDNL1 and FDM2/IDNL2 that is required for RNA-directed DNA methylation (RdDM) and that functions at a downstream step of the RdDM pathway (PubMed:22570638, PubMed:22592791) and downstream of small interfering RNA (siRNA) formation (PubMed:22810086). Required for de novo DNA methylation, siRNA accumulation and siRNA-mediated maintenance methylation (PubMed:19915591). Required for several post-transcriptional gene silencing pathways (PubMed:20059743). Binds double-stranded RNAs (dsRNAs) with 5'-overhangs through its XS domain (PubMed:19915591, PubMed:20059743). Binds long non-coding RNA (lncRNA) in an AGO4-dependent manner and associates with DRM2, resulting in DNA methylation of RdDM target loci (PubMed:23246435, PubMed:24862207). Mediates the silencing of a subset of MORC6 target loci (PubMed:27171427). Interacts with FMD1/IDNL1 (PubMed:22592791). Forms a complex with FMD1/IDNL1 and FMD2/INDL2 (PubMed:22570638, PubMed:22592791). Can form homodimers (PubMed:22570638, PubMed:23246435). Interacts with MORC6 (PubMed:27171427). Late flowering phenotype (PubMed:22592791) and reduction of DNA methylation at RNA-directed DNA methylation (RdDM) target loci (PubMed:19915591, PubMed:20059743, PubMed:22810086, PubMed:22570638, PubMed:22592791).