Cowpea mosaic virus: effects on host cell processes

Abstract

SUMMARYTaxonomy: Cowpea mosaic virus (CPMV) is the type member of the Comoviridae and bears a strong resemblance to animal picornaviruses, both in gene organization and in the amino acid sequence of replication proteins. Little systematic work has been done to compare isolates of the virus from different parts of the world.Physical properties: Purified preparations of virus contain three centrifugal components; empty protein shells without RNA (T) and two nucleoprotein components (M and B), containing 24% and 34% RNA, respectively. The icosahedral particles have with a diameter of 28 nm, consist of 60 copies of two coat proteins, and are heat stable.Hosts: CPMV causes one of the most commonly reported virus diseases of cowpea ( Vigna unguiculata ), in which it produces chlorotic spots with diffuse borders in inoculated primary leaves. Trifoliate leaves develop a bright yellow or light green mosaic of increasing severity in younger leaves. The host range is rather limited, and few hosts are known outside the Leguminosae. The virus is transmitted by various beetles with biting mouthparts. Reported in Africa, the Philippines and Iran. Is apparently absent from North and South America.

Studies on the origin and structure of tubules made by the movement protein of Cowpea mosaic virus

“…; 4 h after embedding), MP-GFP had clearly accumulated in peripheral punctate spots of various sizes and in tubules, as observed previously (Gopinath et al, 2003). Since CPMV RNA2 is translated into two overlapping polyproteins due to the presence of two in-frame start codons (Pouwels et al, 2002a), GFP is also fused to the cofactor for RNA2 replication, which causes fluorescence to accumulate in the nucleus as well (Gopinath et al, 2000;Kasteel et al, 1993;Pouwels et al, 2002b). During the course of the experiment, at the site of some, mostly small, peripheral punctate spots, a tubule was formed ( Fig.…”

“…To determine whether larger proteins could also be accommodated in the plasma membrane around tubules, a construct encoding a fusion between YFP-Zm7hvr and the 110 kDa protein, encoded by CPMV RNA1 (Pouwels et al, 2002a), was used (pMON-110-YFP-Zm7hvr). Protoplasts inoculated with pMON-110-YFP-Zm7hvr revealed that 110-YFP-Zm7hvr also accumulated in the plasma membrane (Fig.…”

“…Cowpea mosaic virus (CPMV), a positive-stranded, bipartite RNA virus belonging to the family Comoviridae, moves from cell to cell by transporting virus particles using tubular structures, which connect the infected cell to the neighbouring uninfected cell (Pouwels et al, 2002a). Immunogold labelling has shown that the CPMV MP is present in these tubular structures (van Lent et al, 1990).…”

“…Normally, only small molecules are able to pass through plasmodesmata, but plant viruses encode one or more proteins, the so-called movement proteins (MPs), that modify the structure of plasmodesmata in such a way that viral transport is enabled. So far, two basic principles for cell-to-cell movement of plant viruses have been described: tubule-guided movement of virus particles and movement as ribonucleoprotein complexes (Lazarowitz & Beachy, 1999).Cowpea mosaic virus (CPMV), a positive-stranded, bipartite RNA virus belonging to the family Comoviridae, moves from cell to cell by transporting virus particles using tubular structures, which connect the infected cell to the neighbouring uninfected cell (Pouwels et al, 2002a). Immunogold labelling has shown that the CPMV MP is present in these tubular structures (van Lent et al, 1990).…”

Secoviridae: a proposed family of plant viruses within the order Picornavirales that combines the families Sequiviridae and Comoviridae, the unassigned genera Cheravirus and Sadwavirus, and the proposed genus Torradovirus

“…1), these viruses share many common features. In addition to having characteristics in common with other picornavirales as discussed above (general capsid structure, polyprotein strategy for [28,30,33,34,43]. In the case of comoviruses, nepoviruses and cheraviruses, experimental evidence has been provided indicating that the tubular structures enable cell-to-cell movement of the virus in the plant and that the viral movement protein is a structural component of the tubules [31,32,46,48,49].…”