Defense Responses Induced by Viral Movement Protein and Its Nuclear Localization Modulate Virus Cell-to-Cell Transport.

Movement proteins (MPs) encoded by plant viruses are essential for cell-to-cell transport of viral genomes through plasmodesmata. The genome of hibiscus green spot virus contains a module of two MP genes termed 'binary movement block' (BMB), encoding the proteins BMB1 and BMB2. Here, BMB1 is shown to induce a defense response in plants that inhibits BMB-dependent virus transport.

Interaction between Movement Proteins of .

Movement proteins (MPs) of plant viruses enable the translocation of viral genomes from infected to healthy cells through plasmodesmata (PD). The MPs functions involve the increase of the PD permeability and routing of viral genome both to the PD entrance and through the modified PD. encodes two MPs, termed BMB1 and BMB2, which act in concert to accomplish virus cell-to-cell transport.

Virus Genome-Based Reporter for Analyzing Viral Movement Proteins and Plasmodesmata Permeability.

Plant virus movement proteins (MPs) mediate cell-to-cell movement of the virus genome through plasmodesmata (PD). MPs target PD to increase their size exclusion limit (SEL), and this MP function is essential for virus intercellular trafficking. In this chapter, we describe the use of a Potato virus X genome-derived reporter for agroinfiltration-based identification of virus genome-encoded MPs and analysis of the ability of individual viral MPs or plant proteins to increase the PD SEL.

Reticulon-like properties of a plant virus-encoded movement protein.

Plant viruses encode movement proteins (MPs) that ensure the transport of viral genomes through plasmodesmata (PD) and use cell endomembranes, mostly the endoplasmic reticulum (ER), for delivery of viral genomes to PD and formation of PD-anchored virus replication compartments. Here, we demonstrate that the Hibiscus green spot virus BMB2 MP, an integral ER protein, induces constrictions of ER tubules, decreases the mobility of ER luminal content, and exhibits an affinity to highly curved membranes. These properties are similar to those described for reticulons, cellular proteins that induce membrane curvature to shape the ER tubules.

RNA phloem transport mediated by pre-miRNA and viral tRNA-like structures.

Phloem-mobile mRNAs are assumed to contain sequence elements directing RNA to the phloem translocation pathway. One of such elements is represented by tRNA sequences embedded in untranslated regions of many mRNAs, including those proved to be mobile. Genomic RNAs of a number of plant viruses possess a 3'-terminal tRNA-like structures (TLSs) only distantly related to genuine tRNAs, but nevertheless aminoacylated and capable of interaction with some tRNA-binding proteins.

Mechanical stress-induced subcellular re-localization of N-terminally truncated tobacco Nt-4/1 protein.

The Nicotiana tabacum 4/1 protein (Nt-4/1) of unknown function expressed in plant vasculature has been shown to localize to cytoplasmic bodies associated with endoplasmic reticulum. Here, we analyzed molecular interactions of an Nt-4/1 mutant with a deletion of 90 N-terminal amino acid residues (Nt-4/1d90) having a diffuse GFP-like localization. Upon transient co-expression with VAP27, a membrane protein known to localize to the ER, ER-plasma membrane contact sites and plasmodesmata, Nt-4/1d90 was concentrated around the cortical ER tubules, forming a network matching the shape of the cortical ER.

Similarities in intracellular transport of plant viral movement proteins BMB2 and TGB3.

The cell-to-cell transport of many plant viruses through plasmodesmata requires viral movement proteins (MPs) encoded by a 'triple gene block' (TGB) and termed TGB1, TGB2 and TGB3. TGB3 is a small integral membrane protein that contains subcellular targeting signals and directs both TGB2 and the helicase domain-containing TGB1 protein to plasmodesmata-associated structures. Recently, we described a 'binary movement block' (BMB) coding for two MPs, BMB1 and BMB2.

RNA helicase domains of viral origin in proteins of insect retrotransposons: possible source for evolutionary advantages.

Recently, a novel phenomenon of horizontal gene transfer of helicase-encoding sequence from positive-stranded RNA viruses to LINE transposons in insect genomes was described. TRAS family transposons encoding an ORF2 protein, which comprised all typical functional domains and an additional helicase domain, were found to be preserved in many families during the evolution of the order Lepidoptera. In the present paper, in species of orders Hemiptera and Orthoptera, we found helicase domain-encoding sequences integrated into ORF1 of retrotransposons of the Jockey family.

Phylogenetic and functional analyses of a plant protein related to human B-cell receptor-associated proteins.

Human B-cell receptor-associated protein BAP31 (HsBAP31) is the endoplasmic reticulum-resident protein involved in protein sorting and transport as well as pro-apoptotic signaling. Plant orthologs of HsBAP31 termed 'plant BAP-like proteins' (PBL proteins) have thus far remained unstudied. Recently, the PBL protein from Nicotiana tabacum (NtPBL) was identified as an interactor of Nt-4/1, a plant protein known to interact with plant virus movement proteins and affect the long-distance transport of potato spindle tuber viroid (PSTVd) via the phloem.

Plant-specific 4/1 polypeptide interacts with an endoplasmic reticulum protein related to human BAP31.

The plant-specific 4/1 protein interacts, both in yeast two-hybrid system and in vitro, and co-localizes in plant cells with plant BAP-like protein, the orthologue of human protein BAP31. In yeast two-hybrid system, we identified a number of Nicotiana benthamiana protein interactors of Nt-4/1, the protein known to affect systemic transport of potato spindle tuber viroid. For one of these interactors, an orthologue of human B-cell receptor-associated protein 31 (BAP31) termed plant BAP-like protein (PBL), the ability to interact with Nt-4/1 was studied in greater detail.

A novel block of plant virus movement genes.

Hibiscus green spot virus (HGSV) is a recently discovered and so far poorly characterized bacilliform plant virus with a positive-stranded RNA genome consisting of three RNA species. Here, we demonstrate that the proteins encoded by the ORF2 and ORF3 in HGSV RNA2 are necessary and sufficient to mediate cell-to-cell movement of transport-deficient Potato virus X in Nicotiana benthamiana. These two genes represent a specialized transport module called a 'binary movement block' (BMB), and ORF2 and ORF3 are termed BMB1 and BMB2 genes.

Translation of the shallot virus X TGB3 gene depends on non-AUG initiation and leaky scanning.

Triple gene block (TGB), a conserved gene module found in the genomes of many filamentous and rod-shaped plant viruses, encodes three proteins, TGB1, TGB2 and TGB3, required for viral cell-to-cell movement through plasmodesmata and systemic transport via the phloem. The genome of Shallot virus X, the type species of the genus Allexivirus, includes TGB1 and TGB2 genes, but contains no canonical ORF for TGB3 protein. However, a TGB3-like protein-encoding sequence lacking an AUG initiator codon has been found in the shallot virus X (ShVX) genome in a position typical for TGB3 genes.