ORIGIN OF THREE RELATED MOVEMENT GENE MODULES IN PLANT VIRUSES: EVOLUTIONARY RADIATIONS OF BENYVIRUS-LIKE RNA REPLICONS
Previous studies have shown that the RNA genomes of some plant viruses encode two related genetic modules required for the virus movement over host body, containing 2 or 3 genes and named as triple gene block (TGB) and binary movement block (BMB). In this paper, we revealed a novel related movement gene module, called Tetra-Cistron Movement Block (TCMB). It was found to be encoded by virus-like transcriptome assemblies of moss Dicranum scoparium and Antarctic flowering plant Colobanthus quitensis. These TCMBs are encoded by second RNA components of the putative two-component viruses related to plant benyviruses. Like RNA-2 of benyviruses, TCMB RNA-2 contains the 5-terminal coat protein gene. General organization of TCMB is very similar to TGB: it includes RNA helicase gene which is followed by two small overlapping cistrons encoding hydrophobic proteins with a distant sequence similarity to TGB2 and TGB3 genes. However, TCMB includes also forth 5-terminal gene coding for protein with an obvious similarity to double-stranded RNA-binding proteins belonging to the DSRM AtDRB-like superfamily. Finally, we suggest the proposed involvement of replicative beny-like helicases in evolution of the BMB and TCMB movement genetic modules.