Notes on Genus: Tritimovirus

flexuous filaments

Type member: Wheat streak mosaic virus

Contents

• Members of this Genus
• General Description
• Morphology
• Electron Micrograph
• Genome
• Genus Genomic Organization
• Genome Map
• Type Member Genomic Organization
• All Known Sequences
• Curated Sequences

General Description

This is one of the genera in the family Potyviridae. Like the other genera, it is characterised by its flexuous filamentous particles, inclusion bodies in infected plant cells and by having a polyprotein genome strategy. It differs from most of the others in having mite transmission and from the genus Bymovirus in having a monopartite genome. The viruses in this genus were previously regarded as members of the genus Rymovirus, but have been separated into a new genus because of substantial differences in nucleotide homology and because the vector is a different species (Aceria tulipae). The genus name is derived from Triticum, the genus name of the host of the type member, wheat streak mosaic virus.

Morphology

Virions filamentous, not enveloped, usually flexuous, 680-750 nm long and 12-15 nm in diameter. Symmetry helical with a pitch of 3.4 nm

Virions composed of 5 % nucleic acid and 95 % protein.

Genome

Monopartite, linear, single stranded, positive sense RNA, 9000-10000 nucleotides long. The 3' terminus has a poly(A) tract and the 5' terminus has a genome-linked protein (VPg).

Genus Genomic Organization

Genome organisation appears to be uniform throughout this genus and is similar to other monopartite members of the family Potyviridae. The genome is translated into a single polyprotein, which is subsequently processed into ten products, with the coat protein at the C-terminus. An additional small ORF (PIPO) is generated by frameshifting within the third (P3) cistron.

Type Member Genomic Organization

The genome is translated into a single polyprotein of 344 kDa, from which an estimated ten functional products are produced by proteolytic processing:

P1 protein	    	putative protease	    	40 kDa
HC-Pro		putative helper component protease	    	44 kDa
P3 protein		unknown function	    	32 kDa
6K1		unknown function	    	6 kDa
CI		Cylindrical inclusion putative helicase	    	73 kDa
6K2		unknown function	    	6 kDa
VPg		Genome-linked protein	    	23 kDa
NIa		Nuclear Inclusion putative protease	    	26 kDa
NIb		Nuclear Inclusion putative polymerase	    	57 kDa
CP		coat protein	    	37 kDa

An additional small ORF (PIPO) is generated by frameshifting within the third (P3) cistron.