Notes on Genus: Bymovirus

flexuous filaments

Type member: Barley yellow 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. Bymoviruses (barley yellow mosaic virus group) are distinguished from other Potyviridae by having bipartite genomes and by 'fungal' transmission. The vector (or putative vector) of all members is a common root-infecting parasite, Polymyxa graminis Ledingham, which is classified in the Plasmodiophorales. Polymyxa graminis and other plasmodiophorid 'fungi' also transmit Furoviruses.

Morphology

Virions filamentous, not enveloped. Of two lengths: 500-600 and 200-300 nm long x 12-15 nm in diameter. Symmetry helical. Pitch of helix 3.4 nm.

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

Genome

Linear, single stranded positive sense RNA. Genome bipartite with total genome 10000-12000 nucleotides long. 3' terminus has a poly(A) tract. 5' terminus has a genome-linked protein (VPg).

Genus Genomic Organization

Each RNA is translated into a polyprotein, which is subsequently processed into a number of structural and non-structural proteins. Many of these have sufficient homology to Potyviruses for functions to be tentatively assigned.

RNA1 is believed to produce 8 peptides:
P3 protein30-40 kDaunknown function
"6K1" 7-8 kDaunknown function
CI 70-75 kDacylindrical inclusion protein with helicase activity and possibly involved in cell to cell movement
"6K2" 7-14 kDaunknown function
VPg 20-22 kDa putative genome-linked protein
NIa-Pro 24-25 kDaSerine-like protease (NIa-Pro).
NIb 59-61 kDahomologous to potyvirus Nuclear Inclusion polymerase
CP 25-35 kDaCoat protein
RNA2 produces 2 peptides:
P1 protein25-30 kDa including a protease domain similar to that of the potyvirus HC-Pro
P2 protein70-75 kDainvolved in fungus transmission. Some laboratory isolates have deletions in this region
An additional small ORF (PIPO) is generated by frameshifting within the first cistron of RNA1 (P3).

Type Member Genomic Organization

Each RNA is translated into a polyprotein, which is subsequently processed into a number of structural and non-structural proteins:
RNA1 is believed to produce 8 peptides:
P3 protein38 kDaunknown function
"6K1" 7 kDaunknown function
CI 74 kDacylindrical inclusion protein with helicase activity and possibly involved in cell to cell movement
"6K2" 14 kDaunknown function
VPg 22 kDa putative genome-linked protein
NIa-Pro 25 kDaSerine-like protease (NIa-Pro).
NIb 60 kDahomologous to potyvirus Nuclear Inclusion polymerase
CP 32 kDaCoat protein
RNA2 produces 2 peptides:
P1 protein28 kDa including a protease domain similar to that of the potyvirus HC-Pro
P2 protein70 kDainvolved in fungus transmission
An additional small ORF (PIPO) is generated by frameshifting within the first cistron of RNA1 (P3).