RNA-directed RNA polymerase that is involved in both transcription and genome replication. Together with VP3 capping enzyme, forms an enzyme complex positioned near the channels situated at each of the five-fold vertices of the core. Following infection, the outermost layer of the virus is lost, leaving a double-layered particle (DLP) made up of the core and VP6 shell. VP1 then catalyzes the transcription of fully conservative plus-strand genomic RNAs that are extruded through the DLP's channels into the cytoplasm where they function as mRNAs for translation of viral proteins. One copy of each of the viral (+)RNAs is also recruited during core assembly, together with newly synthesized polymerase complexes and VP2. The polymerase of these novo-formed particles catalyzes the synthesis of complementary minus-strands leading to dsDNA formation. To do so, the polymerase specifically recognizes conserved 3' sequence(s) in plus-strand RNA templates. Once dsRNA synthesis is complete, the polymerase switches to the transcriptional mode, thus providing secondary transcription (By similarity). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Interacts with VP3 (Potential). Interacts with VP2 (Potential). Interacts with NSP5; this interaction is probably necessary for the formation of functional virus factories (By similarity). Attached inside the inner capsid as a minor component. Also found in spherical cytoplasmic structures, called virus factories, that appear early after infection and are the site of viral replication and packaging (By similarity). Belongs to the reoviridae RNA-directed RNA polymerase family.