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

Shreya Saha,Kristiina Mäkinen

doi:10.3390/v12020197

Abstract

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.

Highlights

Plant–pathogen interactions are an outcome of co-evolution
A testable hypothesis for future studies based on these results is that the binding of eIF(iso)4E to potato virus A (PVA) viral protein genome-linked (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
The alignment of 112 potyviral VPgs revealed that the putative eIF4E binding site YXXXLΦ, which can be found in the central region of PVA VPg (YTDIRLI, amino acids 89–95 of PVA VPg), is not conserved throughout potyviruses

Summary

Introduction

Plant–pathogen interactions are an outcome of co-evolution. Viruses, being obligate parasites, depend entirely on the host for their survival. The most evolved and widespread pathogens indicate better adaptability with variable hosts. Potyviruses comprise a large group of agriculturally and economically important plant viruses. The family Potyviridae includes the genus Potyvirus and nine other genera. Due to their economic and scientific importance, two potyviruses, namely potato virus Y (PVY) and plum pox virus (PPV), have been designated as being among the top ten most important plant viruses [1]

Methods

Results

Conclusion