Viruses belonging to this superfamilly bear strong resemblance to animal picornaviruses both in gene organization and in the amino acid sequence of replication proteins. In plants, the genome of picorna-like viruses can be monopartite such as in Potyviridae or distributed over two RNAs as in members of the Comoviridae family. The RNAs of these viruses are characterized by a covalently genome-linked protein (VPg) at the 5' end, a unique open reading frame encoding a single polyprotein and a poly (A) tail at the 3'-terminus. Within the Potyvirida, the Tobacco etch virus 6-kDa protein has been shown to localize specifically to ER membranes when expressed as a fusion with GFP or glucuronidase and was proposed to cause the ER modifications that are observed during Tobacco etch virus infection (Schaad et al. 1997). Here, the analysis has been restricted to some of the best-studied Comoviridae members such as Cowpea mosaic virus (CPMV), the type member of the genus Comovirus, and two nepoviruses, the Tomato ringspot virus (ToRSV) and the Grapevine fanleaf virus (GFLV).
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