English: Branch 2 of the RNA virus RNA-dependent RNA polymerases (RdRps): “picornavirus supergroup” of the +RNA viruses expanded to include nidoviruses and two groups of dsRNA viruses, partitiviruses, and picobirnaviruses. (A) Phylogenetic tree of the virus RdRps showing ICTV accepted virus taxa and other major groups of viruses. Approximate numbers of distinct virus RdRps present in each branch are shown in parentheses. Symbols to the right of the parentheses summarize the presumed virus host spectrum of a lineage. Green dots represent well-supported (≥0.7) branches. Inv., viruses of invertebrates (many found in holobionts, making host assignment uncertain); myco., mycoviruses; Uncl., unclassified; vert., vertebrate. (B) Genome maps of a representative set of branch 2 viruses (drawn to scale) showing color-coded major conserved domains. Where a conserved domain comprises only a part of the larger protein, the rest of this protein is shown in light gray. The locations of such domains are approximated (indicated by fuzzy boundaries). 3Cpro, 3C chymotrypsin-like protease; CP, capsid protein; E, envelope protein; En, nidoviral uridylate-specific endoribonuclease (NendoU); Exo, 3′-to-5′ exoribonuclease domain; fCP, capsid protein forming filamentous virions; M, membrane protein; MD, macrodomain; MP, movement protein; MT, ribose-2-O-methyltransferase domain; N, nucleocapsid protein; N7, guanine-N7-methyltransferase; Ppro, papain-like protease; SJR1 and SJR2, single jelly-roll capsid proteins of type 1 and type 2; spike, spike protein; S1H, superfamily 1 helicase; S2H, superfamily 2 helicase; S3H, superfamily 3 helicase; VP2, virion protein 2; Z, Zn-finger domain; Spro, serine protease; P3, protein 3. Distinct hues of same color (e.g., green for MPs) are used to indicate cases where proteins that share analogous function are not homologous.