The functional analysis of distinct tospovirus movement proteins (NS M ) reveals different capabilities in tubule formation, cell-to-cell and systemic virus movement among the tospovirus species

Abstract

The lack of infectious tospovirus clones to address reverse genetic experiments has compromised the functional analysis of viral proteins. In the present study we have performed a functional analysis of the movement proteins (NS) of four tospovirus species Bean necrotic mosaic virus (BeNMV), Chrysanthemum stem necrosis virus (CSNV), Tomato chlorotic spot virus (TCSV) and Tomato spotted wilt virus (TSWV), which differ biologically and molecularly, by using the Alfalfa mosaic virus (AMV) model system. All NS proteins were competent to: i) support the cell-to-cell and systemic transport of AMV, ii) generate tubular structures on infected protoplast and iii) transport only virus particles. However, the NS of BeNMV (one of the most phylogenetically distant species) was very inefficient to support the systemic transport. Deletion assays revealed that the C-terminal region of the BeNMV NS, but not that of the CSNV, TCSV and TSWV NS proteins, was dispensable for cell-to-cell transport, and that all the non-functional C-terminal NS mutants were unable to generate tubular structures. Bimolecular fluorescence complementation analysis revealed that the C-terminus of the BeNMV NS was not required for the interaction with the cognate nucleocapsid protein, showing a different protein organization when compared with other movement proteins of the '30K family'. Overall, our results revealed clearly differences in functional aspects among movement proteins from divergent tospovirus species that have a distinct biological behavior.

Intracellular Localization, Interactions and Functions of Capsicum Chlorosis Virus Proteins

“…INSV and IYSV NSm did not have punctate distribution on the cell periphery suggesting these proteins do not form visible aggregates at PD (Dietzgen et al, 2012; Tripathi et al, 2015a). Taken together, localization and interaction profiles of tospovirus NSm proteins studied so far indicate potentially different strategies for intracellular trafficking, PD localization, and cell-to-cell movement (Paape et al, 2006; Dietzgen et al, 2012; Leastro et al, 2015, 2017; Singh and Savithri, 2015; Tripathi et al, 2015b; Feng et al, 2016). We speculate that different interacting host factors may be responsible for these differences.…”

Specificity of Plant Rhabdovirus Cell-to-Cell Movement

“…Therefore, movement specificity can be achieved through these interactions. In addition to unsegmented plant rhabdoviruses, MP-N interactions have been described for various tripartite NS tospoviruses (75)(76)(77)(78)(79)(80), suggesting that conserved movement mechanisms may exist across NS RNA virus families. Notably, for positive-stranded RNA viruses requiring the CP for cell-to-cell transit, e.g., alfamo-, bromo-, como-, cucumo-, clostero-, potex-, and potyviruses, specific binding of MPs to cognate CPs or virions has also been reported (see reference 81 and references therein).…”

Dissecting the Subcellular Localization, Intracellular Trafficking, Interactions, Membrane Association, and Topology of Citrus Leprosis Virus C Proteins

“…Considering that CiLV-C has a natural limitation in ensuring the systemic viral spread, though speculative, there is a possibility that the inability of the MP to interact in vivo may have direct involvement with this phenotype. Experiments that evaluate the efficiency of viral movement from the insertion of the CiLV-C MP in heterologous system, i.e., TMV (Lewandowski and Adkins, 2005 ) or Alfalfa mosaic virus (AMV) model systems (Sanchez-Navarro et al, 2001 ; Leastro et al, 2017 ) will help to clarify this question. It is important to note that some protein interactions may only occur in the presence of virus replication, requiring more than one interaction partner (Dietzgen et al, 2012 ).…”