DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Second largest core component of RNA polymerase I which synthesizes ribosomal RNA precursors. Proposed to contribute to the polymerase catalytic activity and forms the polymerase active center together with the largest subunit. Pol I is composed of mobile elements and NRPA2 is part of the core element with the central large cleft and probably a clamp element that moves to open and close the cleft. Essential for the completion of the three rounds of mitosis in female megaspores required for the development of mature gametophytes. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Component of the RNA polymerase I (Pol I) complex consisting of at least 13 subunits. Defect in seed production due to female gametophyte developmental arrest. Belongs to the RNA polymerase beta chain family.