Is an RNA-dependent RNA polymerase active in viral RNA replication. Is a methyltransferase active in RNA capping and an RNA helicase. Methyltransferase displays a cytoplasmic capping enzyme activity. This function is necessary since all viral RNAs are synthesized in the cytoplasm, and host capping enzymes are restricted to the nucleus. Helicase region probably exhibits NTPase and RNA unwinding activities (Potential). It also acts as a suppressor of RNA-mediated gene silencing, also known as post-transcriptional gene silencing (PTGS), a mechanism of plant viral defense that limits the accumulation of viral RNAs. May mediate silencing suppression through either inhibition of HEN1-mediated siRNA or siRNA demethylation (By similarity). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) ATP + H2O = ADP + H(+) + phosphate In resistant plants, is bound by host protein Tm-1 (e.g tomato Tm-1 AC A7M6E7), thereby inhibiting replication complex activity. Heterodimer of a large and a small subunit (By similarity). Both large and small subunits interact, via an ATP bridge, with host protein Tm-1 (e.g. tomato Tm-1 AC A7M6E7 and AC A7M6E8) (PubMed:19423673). This protein is translated as a fusion protein by episodic readthrough of a termination codon. When readthrough of the terminator codon TGA occurs between the codons for Arg-1111 and Gln-1113, this results in the addition of the RdRp region to the replicase. Belongs to the ssRNA positive-strand viruses RNA-directed RNA polymerase family.