Notes on Genus: Fabavirus
Type member: Broad bean wilt virus 1
This is one of 3 genera in the subfamily Comovirinae
of the plant picornavirus family Secoviridae
and derives its name from the scientific name of the host (Vicia faba
) of the type member (broad bean wilt virus 1). In common with other genera in the subfamily, its members are characterised by their bipartite genome encapsidated in icosahedral particles with each genome segment producing a polyprotein. Although originally included in the genus Comovirus
, Fabaviruses are serologically unrelated to members of that genus and are transmitted by aphids (rather than beetles).
Virions isometric (icosahedral), not enveloped, of two types but similar in size (about 30 nm in diameter) and appearance. Nucleocapsids appear to be angular.
Virions composed of 25 % nucleic acid (M component), or 35 % nucleic acid (B component).
Bipartite, linear, single stranded, positive sense RNA. The genome segments are encapsidated separately into different types of particles: RNA1 (c.
6000 nucleotides) into B and RNA2 (c.
3600 nucleotides) into M particles. The 3' terminus of each RNA has a poly(A) tract and the 5' terminus probably has a genome-linked protein (VPg).
Genus Genomic Organization
Each RNA is translated into a polyprotein, which is then processed by a series of steps into functional proteins: RNA1 encodes proteins necessary for replication while two coat proteins and a cell-to-cell movement product are encoded on RNA2.
Type Member Genomic Organization
Each RNA is translated into a polyprotein, which is then processed by a series of steps into functional proteins:
|RNA1 produces a polyprotein of 206 kDa processed into 5 peptides necessary for replication:|
|1. || 35 kDa||Processing regulator (protease co-factor)|
|2. ||66 kDa||Nucleotide binding protein with helicase activity|
|3. ||3.1 kDa||VPg: genome-linked protein|
|4. ||23 kDa ||Protease|
|5. ||79 kDa ||Polymerase|
|RNA2 produces a polyprotein of 114 kDa processed into 3 functional peptides: |
|1. ||47 kDa ||Movement protein|
|2. ||44 kDa||Large coat protein|
|3. ||23 kDa||Small coat protein|