An Isoform of the Eukaryotic Translation Elongation Factor 1A (eEF1a) Acts as a Pro-Viral Factor Required for Tomato Spotted Wilt Virus Disease in Nicotiana benthamiana

Tieme Helderman,Marcel Prins,Sjef Boeren,André Bertran,Harrold Van Den Burg,Matthieu Joosten,Richard Kormelink,Like Fokkens,Laurens Deurhof

doi:10.3390/v13112190

Abstract

The tripartite genome of the negative-stranded RNA virus Tomato spotted wilt orthotospovirus (TSWV) is assembled, together with two viral proteins, the nucleocapsid protein and the RNA-dependent RNA polymerase, into infectious ribonucleoprotein complexes (RNPs). These two viral proteins are, together, essential for viral replication and transcription, yet our knowledge on the host factors supporting these two processes remains limited. To fill this knowledge gap, the protein composition of viral RNPs collected from TSWV-infected Nicotiana benthamiana plants, and of those collected from a reconstituted TSWV replicon system in the yeast Saccharomyces cerevisiae, was analysed. RNPs obtained from infected plant material were enriched for plant proteins implicated in (i) sugar and phosphate transport and (ii) responses to cellular stress. In contrast, the yeast-derived viral RNPs primarily contained proteins implicated in RNA processing and ribosome biogenesis. The latter suggests that, in yeast, the translational machinery is recruited to these viral RNPs. To examine whether one of these cellular proteins is important for a TSWV infection, the corresponding N. benthamiana genes were targeted for virus-induced gene silencing, and these plants were subsequently challenged with TSWV. This approach revealed four host factors that are important for systemic spread of TSWV and disease symptom development.

Highlights

Viruses belonging to the family Tospoviridae cause severe problems in agriculture worldwide
As N. benthamiana is hypersusceptible to Tomato spotted wilt orthotospovirus (TSWV), viral ribonucleoprotein complexes (RNPs) isolated from this plant species are likely to contain host proteins crucial for the viral infection cycle, such as viral transcription, translation, assembly, and cell-to-cell movement
The N. benthamiana plants inoculated with control samples did not develop TSWV disease symptoms, while the plants inoculated with TSWV RNP samples did

Summary

Introduction

Viruses belonging to the family Tospoviridae cause severe problems in agriculture worldwide. Engineered mutant alleles of these S genes are widely regarded to be an effective means to obtain sustainable resistance to plant viruses [5,6]. To this date, only four candidate S genes have been reported for TSWV, that is, 9-lipoxygenase (9LOX) and α-dioxygenases (α-DOX) in Arabidopsis [7], root hair defective 3 (rhd3) in Arabidopsis [8], and suppressor of the G2 allele of skp (SGT1) in N. benthamiana [9]. We report on the identification of novel candidate S genes for TSWV, using a proteomics approach that aimed to identify the host protein associated with viral ribonucleoprotein complexes (RNPs) and confirmed, by gene silencing, their role as a pro-viral host factor for TSWV

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