RNA-dependent direct polymerase involved in the production of small interfering RNAs (siRNAs). Binds to single-stranded RNA (ssRNA); engages ssRNAs longer than 7 nucleotides and initiates internal to their 3' ends (PubMed:34903670). Able to transcribe the RNA of an RNA/DNA hybrid, the transcript produced by Pol IV, if its 3' end is accessible, to generate double-stranded small interfering RNAs (dsRNAs) precursor essential for establishing and maintaining DNA methylation (PubMed:34903670, PubMed:34941388). Required for the biogenesis of endogenous siRNAs of 24 nucleotide which derive from heterochromatin and DNA repeats such as transposons or endogenous gene tandem repeats, such as repeats present in FWA gene. Involved in transcriptional gene silencing (TGS). Component of the RNA-directed DNA methylation (RdDM) silencing pathway that utilizes siRNAs to guide DNA methyltransferases to asymmetric cytosines. Involved in control of flowering time through RdDM of FWA locus. Required for reception of long-distance mRNA silencing in the shoot. Required for the formation of telomeric siRNAs and the RNA-dependent DNA methylation of asymmetric cytosines in telomeric (5'-CCCTAAA-3') repeats. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Interacts with NRPD1 and SHH1. Associates with Pol IV complex, forming an interpolymerase channel bridging their active sites, through which the Pol IV-generated transcript is handed over to the RDR2 active site after being backtracked, where it is used as the template for double-stranded RNA (dsRNA) synthesis (PubMed:34941388). Interacts with JMJ24 (PubMed:26119694). In the nucleolus, localized in a ring or crescent around the inner periphery and to a distinctive nucleolar dot. Late flowering and absence of siRNAs derived from FWA tandem repeat regions. Loss of de novo methylation. Increased expression of retrotransposon-derived solo long terminal repeat (solo LTR) and SDC due to their derepression; levels are even higher in the double mutant rdr2-1 jmj24-1 (PubMed:26119694). RDR2 is non-functional in the absence of associated Pol IV. Belongs to the RdRP family.