A Novel Interaction Network Used by Potyviruses in Virus-Host Interactions at the Protein Level.

Marjo Ala-Poikela,Jari P.T Valkonen,Minna-Liisa Rajamäki

doi:10.3390/v11121158

Marjo Ala-Poikela, Jari P.T Valkonen + Show 1 more

Open Access

https://doi.org/10.3390/v11121158

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Journal: Viruses	Publication Date: Dec 14, 2019
Citations: 18	License type: CC BY 4.0

Affiliation: University of Helsinki

Abstract

Host proteins that are central to infection of potyviruses (genus Potyvirus; family Potyviridae) include the eukaryotic translation initiation factors eIF4E and eIF(iso)4E. The potyviral genome-linked protein (VPg) and the helper component proteinase (HCpro) interact with each other and with eIF4E and eIF(iso)4E and proteins are involved in the same functions during viral infection. VPg interacts with eIF4E/eIF(iso)4E via the 7-methylguanosine cap-binding region, whereas HCpro interacts with eIF4E/eIF(iso)4E via the 4E-binding motif YXXXXLΦ, similar to the motif in eIF4G. In this study, HCpro and VPg were found to interact in the nucleus, nucleolus, and cytoplasm in cells infected with the potyvirus potato virus A (PVA). In the cytoplasm, interactions between HCpro and VPg occurred in punctate bodies not associated with viral replication vesicles. In addition to HCpro, the 4E-binding motif was recognized in VPg of PVA. Mutations in the 4E-binding motif of VPg from PVA weakened interactions with eIF4E and heavily reduced PVA virulence. Furthermore, mutations in the 4G-binding domain of eIF4E reduced interactions with VPg and abolished interactions with HCpro. Thus, HCpro and VPg can both interact with eIF4E using the 4E-binding motif. Our results suggest a novel interaction network used by potyviruses to interact with host plants via translation initiation factors.

Highlights

The genus Potyvirus contains the largest number of plant-infecting RNA viruses that cause yield losses in all major crops [1]
Expression of VPg-red fluorescent protein (RFP) in the leaves of N. benthamiana after agroinfiltration revealed red fluorescence predominantly in the nucleus, whereas RFP-helper component-proteinase (HCpro) expressed in the same manner was detected mainly in the cytoplasm (Figure 1A)
The VPg–HCpro interaction was detected in the cytoplasm and in a subcellular compartment that was presumably the nucleus by epifluorescence microscopy (Figure 1B) using the Bimolecular Fluorescence Complementation (BiFC) assay [53] with HCpro and VPg tagged with the C- or N-proximal half of the yellow fluorescent protein (YFP)

Summary

Introduction

The genus Potyvirus (family Potyviridae) contains the largest number of plant-infecting RNA viruses that cause yield losses in all major crops [1]. The potyvirus genome is a monopartite, positive-strand RNA—(+)ssRNA—that contains the viral genome-linked protein (VPg) covalently bound to its 5’ end [2,3]. One or two additional proteins are produced by a frame-shifting mechanism [4,5,6,7]. The most comprehensively studied recessive genes used to breed resistance to potyviruses in crop plants encode variants of eukaryotic translation initiation factor 4E (eIF4E) or iso4E [eIF(iso)4E] [8,9,10]. We refer to both translation initiation factors with the abbreviation 4E, unless the factor needs to be specified

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