Chimeras between Oilseed rape mosaic virus and Tobacco mosaic virus highlight the relevant role of the tobamoviral RdRp as pathogenicity determinant in several hosts

Abstract

Oilseed rape mosaic virus (ORMV) is a tobamovirus taxonomically distinct from the type member of the genus, Tobacco mosaic virus (TMV). Both viruses display a specific host range, although they share certain hosts, such as Arabidopsis thaliana, Nicotiana benthamiana and N. tabacum, on which they induce different symptoms. Using a gain-of-symptom approach, we generated chimeric viruses, starting from a TMV infectious clone, over which different regions of ORMV were exchanged with their corresponding regions in the TMV genome. This approach allowed the association of pathogenicity determinants to certain genes within the ORMV genome. A general trend was observed associating the viral origin of the RNA-dependent RNA-polymerase (RdRp) gene and the gain of symptoms. In A. thaliana and N. benthamiana, chimeric viruses were unable to reproduce the symptoms induced by the parental viruses, leading to disease states which could be described as intermediate, and variable in some cases. In contrast, a hypersensitive reaction caused by both of these viruses on N-gene-bearing tobaccos could be found in resistance reactions to all chimeric viruses, suggesting that the avirulence determinant maps similarly in both viruses. A systemic necrotic spotting typical of non-N-gene tobaccos infected with ORMV was associated with the polymerase domain of RdRp. To our knowledge, this is the first time that this controversial portion of the tobamovirus genome has been identified directly as a pathogenicity determinant. None of the reactions of the chimeric viruses could be correlated with increases or decreases in virus titres in the infections.

The 50 distal amino acids of the 2AHP homing protein of Grapevine fanleaf virus elicit a hypersensitive reaction on Nicotiana occidentalis

“…Alternatively, as protein 2A HP is involved in RNA2 replication (Gaire et al, 1999), and thus indirectly in encapsidation and movement, the host resistance gene could act directly by inhibiting virus replication and movement. However, many Avr factors act independently of virus accumulation (Hasi ow-Jaroszewska et al, 2011; Mansilla et al, 2009;Schoelz, 2006). Future experiments will aim to uncouple these two functions of GFLV protein 2A HP .…”

Differential mRNA Accumulation upon Early Arabidopsis thaliana Infection with ORMV and TMV-Cg Is Associated with Distinct Endogenous Small RNAs Level

“…thaliana Col-0 plants were grown under standard conditions [ 27 ] in controlled environmental chambers (22°C 16/8 h light/dark). To quantify TMV-Cg [ 28 ] and ORMV [ 29 ] inoculum, N . tabacum (NN) plants were infected from serial dilutions of viral extracts.…”

Myosins VIII and XI Play Distinct Roles in Reproduction and Transport of Tobacco Mosaic Virus

“…Single infection sites of TMV-GFP formed in the presence of expressed myosin tails or RFP as control were excised at 4 dpi and total RNA was extracted using TR-Reagent (SIGMA) according to the manufacturer's instructions. RNA of TMV-GFP was quantified by qRT-PCR using 50 ng of total RNA and specific primers and probe [63] . qRT-PCR with known concentrations of TMV RNA in the solution was used to establish a standard curve from which the number of TMV-GFP RNA copies per ng of total RNA was determined.…”