RNA-dependent RNA polymerase that plays an essential role in the virus replication. Induces the reorganization of host mitochondria and the formation of structures with numerous dilations surrounded by double membranes, which may provide a protected environment to viral replication. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) This protein is translated as a fusion protein by episodic readthrough of P29 termination codon. Readthrough of the terminator codon TAG occurs between the codons for 268-Asn and 270-Gly. Belongs to the tombusviridae RNA polymerase family.