Probably contains methyltransferase and helicase activities (PubMed:2209552). Methyltransferase displays a cytoplasmic capping enzyme activity (Probable). This function is necessary since all viral RNAs are synthesized in the cytoplasm, and host capping enzymes are restricted to the nucleus (Probable). Helicase region probably exhibits NTPase and RNA unwinding activities (Probable). ATP + H2O = ADP + H(+) + phosphate Interacts with the suppressor of RNA silencing Gamma-B (via C-terminus). The viral replication sites are located at the host chloroplast membrane. The genome of this virus consists of three linear, positive, single-stranded RNAs encapsidated in separate virions designated RNA-alpha, RNA-beta and RNA-gamma. Three proteins (alpha-A, beta-A and gamma-A) are translated directly from these genomic RNAs and the remaining proteins encoded on RNA-beta (beta-B, beta-C and beta-D) and RNA-gamma (gamma-B) are expressed via three subgenomic messenger RNAs.