CASSAVA VEIN MOSAIC-VIRUS (CSVMV), TYPE SPECIES FOR A NEW GENUS OF PLANT DOUBLE-STRANDED DNA VIRUSES

The complete sequence of 8159 nucleotides of the double stranded DNA g enome of cassava vein mosaic virus (CsVMV) was determined (# U59751) a nd revealed a significant difference in genome organization when compa red with a previous report (# U20341). When transferred to cassava pla nts by microbombardment, the full length CsVMV clone was infectious, c onfirming the genome organization here described. Sequence comparisons between CsVMV and members of the genera Caulimovirus and Badnavirus r evealed high homologies between consensus sequences of several protein s that are indispensable for virus replication, including a potential transactivator factor not reported previously. The presence of a seque nce complementary to a plant Met tRNA confirms that CsVMV is a plant p araretrovirus and is most closely related to members of the genus Caul imovirus as previously assessed. However, differences in genome organi zation, number and size of the ORFs, in addition to sequence compariso ns with other plant pararetroviruses, shows that either the genetic va riability of caulimoviruses is much greater than previously thought, o r that CsVMV is the unique representative of a new genus within the Ca ulimoviridae family. On the basis of this study, it is proposed to upg rade the floating genus Caulimovirus to the family level and to divide the Caulimoviridae family into at least three genera with CsVMV being the type member of a new genus.