A movement protein and three capsid proteins are all necessary for the cell-to-cell movement of apple latent spherical cheravirus

Abstract

Immunoblot analysis of apple latent spherical cheravirus (ALSV)-infected leaves using a polyclonal antibody against the 21 C-terminal amino acids of a 53 K/42 K movement protein (MP) showed that a protein with an Mr of 42 kDa (42KP) is the dominant form found in vivo, which could indicate that the second AUG is used as an initiation codon of a ORF in RNA2. Co-expression of GFP with 42KP in tobacco epidermal cells showed that 42KP is able to facilitate cell-to-cell trafficking of GFP that is expressed in the same cells. The analysis of deletion mutants on each of MP, Vp24, Vp20, or Vp25 using an ALSV vector that stably expresses GFP indicated that an MP and three capsid proteins are all indispensable for the cell-to-cell movement of the virus. In ultrathin sections of infected leaves, a file of virus-like particles passing through the plasmodesmata connecting neighboring cells and tubular structures containing virus-like particles extending into the cytoplasm were observed. These results show that ALSV moves from cell to cell as virus particles.

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

“…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]. The mechanism of cell-to-cell movement has not yet been elucidated for other viruses.…”

Promotion of flowering and reduction of a generation time in apple seedlings by ectopical expression of the Arabidopsis thaliana FT gene using the Apple latent spherical virus vector

“…ALSV-RNA 1 is 6813 nt long excluding the 3 0 poly(A) tail and has a single open reading frame (ORF) encoding a replication-associated protein of 243 K (Li et al 2000). RNA 2 is 3385 nt long excluding the 3 0 poly (A) tail, and also has a single ORF encoding a 42 K movement protein (MP) on the N-terminal side and three capsid proteins in the C-terminal region (Li et al 2000;Yoshikawa et al 2006). The virus was originally isolated from an apple tree in Japan (Koganezawa et al 1985), and shown to infect apple latently (Ito and Yoshida 1997).…”

“…ALSV-based vector was constructed from the infectious cDNA clone of RNA2 (pEALSR2) by duplication of protease cleavage site between the C terminus of MP and the N terminus of Vp25 (Li et al 2004) and have been used for expression of foreign genes and silencing of endogenous genes in plants (Igarashi et al 2009;Li et al 2004;Takahashi et al 2007;Yaegashi et al 2007;Yoshikawa et al 2006).…”

Seed and pollen transmission of Apple latent spherical virus in apple

“…RNA 1 is 6813 nt long excluding the 3 0 poly(A) tail and has a single open reading frame (ORF) encoding a replication-associated protein of 243 K (Li et al 2000). RNA 2 is 3385 nt long excluding the 3 0 poly (A) tail, and also has a single ORF encoding a 42 kDa movement protein (MP) on the N-terminal side and three capsid proteins in the C-terminal region (Li et al 2000;Yoshikawa et al 2006).…”