The N-terminal fragment of the tomato torrado virus RNA1-encoded polyprotein induces a hypersensitive response (HR)-like reaction in Nicotiana benthamiana.

Przemysław Wieczorek,Aleksandra Obrępalska-Stęplowska

doi:10.1007/s00705-016-2841-8

Przemysław Wieczorek, Aleksandra Obrępalska-Stęplowska

Open Access

https://doi.org/10.1007/s00705-016-2841-8

Copy DOI

Abstract

The hypersensitive response (HR) is a defence reaction observed during incompatible plant-pathogen interactions in plants infected with a wide range of fungi, bacteria and viruses. Here, we show that an N-terminal polyprotein fragment encoded by tomato torrado virus RNA1, located between the first ATG codon and the protease cofactor (ProCo) motif, induces an HR-like reaction in Nicotiana benthamiana. Agrobacterium tumefaciens-mediated transient expression of the first 105 amino acids (the calculated molecular weight of the fragment was ca. 11.33 kDa, hereafter refered to as the 11K domain) from ToTV RNA1 induced an HR-like phenotype in infiltrated leaves. To investigate whether the 11K domain could influence the virulence and pathogenicity of a recombinant virus, we created a potato virus X (PVX) with the 11K coding sequence inserted under a duplicated coat protein promoter. We found that 11K substantially increased the virulence of the recombinant virus. Disease phenotype induced in N. benthamiana by PVX-11K was characterized by strong local and systemic necrosis. This was not observed when the 11K domain was expressed from PVX in an antisense orientation. Further analyses revealed that the 11K domain could not suppress posttranscriptional gene silencing (PTGS) of green fluorescent protein (GFP) in the N. benthamiana 16c line. In silico analysis of the predicted secondary structure of the 11K domain indicated the presence of two putative helices that are highly conserved in tomato-infecting representatives of the genus Torradovirus.

Highlights

Interactions between plants and pathogens represent an everlasting arms race between the invader and the host
To investigate the biological function of the 11K domain, which is composed of 105 amino acid residues upstream of the protease cofactor (ProCo) motif encoded on Tomato torrado virus (ToTV) RNA1 (Fig. 1B), the coding region between the 5’UTR and the ProCo motif was amplified by reverse transcription (RT)-polymerase chain reaction (PCR) and was inserted into the pBIN61 vector
The results indicated that the levels of accumulated genomic and subgenomic (25K and coat proteins (CP) genes) PVX RNAs were comparable in plants infected with PVX, Fig. 3 The 11K domain enhances virulence of a chimeric potato virus X (PVX) in Nicotiana benthamiana

Summary

Introduction

Interactions between plants and pathogens represent an everlasting arms race between the invader and the host. These interactions take place at the molecular level, involving nucleic acids and proteins of the pathogens (fungi, bacteria, viruses) as well as those of the plant. Viruses take advantage of the cellular machinery to replicate and spread within the host. This reprograms cell metabolism and leads to a sequence of events that negatively affect the development of the invaded plant. Some viruses induce systemic necrosis in the plant upon infection [1]. Systemic necrosis has been proposed to share some biochemical and physiological features with programmed cell death (PCD) [3]

Methods

Results

Conclusion