DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Component of RNA polymerase V involved in RNA-directed DNA methylation-dependent (RdDM) silencing of endogenous repeated sequences, including transposable elements. Required for establishment of DNA methylation. Component of the RNA polymerase V complex. Expressed in roots, leaves, siliques and seeds, and to a lower level, in flower buds and flowers. Partial loss of methylation and silencing of RdDM targets, probably due to the redundancy with NRPE5B. Belongs to the archaeal Rpo5/eukaryotic RPB5 RNA polymerase subunit family.