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Open AccessArticle

Insights into the Functions of eIF4E-Binding Motif of VPg in Potato Virus A Infection

Department of Microbiology and Viikki Plant Science Centre, University of Helsinki, 00014 Helsinki, Finland
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Author to whom correspondence should be addressed.
Viruses 2020, 12(2), 197; https://doi.org/10.3390/v12020197
Received: 2 January 2020 / Revised: 5 February 2020 / Accepted: 7 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue The Complexity of the Potyviral Interaction Network)
The interaction between the viral protein genome-linked (VPg) and eukaryotic initiation factor 4E (eIF4E) or eIF(iso)4E of the host plays a crucial role in potyvirus infection. The VPg of potato virus A (PVA) contains the Tyr-X-X-X-X-Leu-phi (YXXXLΦ) binding motif for eIF(iso)4E. In order to investigate its role in PVA infection, we substituted the conserved tyrosine and leucine residues of the motif with alanine residues in the infectious cDNA of PVA (PVAVPgmut). PVAVPgmut RNA replicated in infiltrated leaves, but RNA accumulation remained low. Systemic infection occurred only if a reversion to wild type PVA occurred. VPg was able to stabilize PVA RNA and enhance the expression of Renilla luciferase (3’RLUC) from the 3’ end of the PVA genome. VPgmut could not support either PVA RNA stabilization or enhanced 3’RLUC expression. The RNA silencing suppressor helper-component proteinase (HCPro) is responsible for the formation of PVA-induced RNA granules (PGs) during infection. While VPgmut increased the number of PG-like foci, the percentage of PVA RNA co-localization with PGs was reduced from 86% to 20%. A testable hypothesis for future studies based on these results is that the binding of eIF(iso)4E to PVA VPg via the YXXXLΦ motif is required for PVA RNA stabilization, as well as the transfer to the RNA silencing suppression pathway and, further, to polysomes for viral protein synthesis.
Keywords: potato virus A; potyvirus; viral protein genome-linked; eukaryotic initiation factor 4E/(iso)4E; potyvirus-induced RNA granules; RNA silencing; RNA silencing suppression potato virus A; potyvirus; viral protein genome-linked; eukaryotic initiation factor 4E/(iso)4E; potyvirus-induced RNA granules; RNA silencing; RNA silencing suppression
MDPI and ACS Style

Saha, S.; Mäkinen, K. Insights into the Functions of eIF4E-Binding Motif of VPg in Potato Virus A Infection. Viruses 2020, 12, 197.

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