Tobacco mosaic virus 126-kDa Protein Increases the Susceptibility of Nicotiana tabacum to Other Viruses and Its Dosage Affects Virus-Induced Gene Silencing

Abstract

The Tobacco mosaic virus (TMV) 126-kDa protein is a suppressor of RNA silencing previously shown to delay the silencing of transgenes in Nicotiana tabacum and N. benthamiana. Here, we demonstrate that expression of a 126-kDa protein-green fluorescent protein (GFP) fusion (126-GFP) in N. tabacum increases susceptibility to a broad assortment of viruses, including Alfalfa mosaic virus, Brome mosaic virus, Tobacco rattle virus (TRV), and Potato virus X. Given its ability to enhance TRV infection in tobacco, we tested the effect of 126-GFP expression on TRV-mediated virus-induced gene silencing (VIGS) and demonstrate that this protein can enhance silencing phenotypes. To explain these results, we examined the poorly understood effect of suppressor dosage on the VIGS response and demonstrated that enhanced VIGS corresponds to the presence of low levels of suppressor protein. A mutant version of the 126-kDa protein, inhibited in its ability to suppress silencing, had a minimal effect on VIGS, suggesting that the suppressor activity of the 126-kDa protein is indeed responsible for the observed dosage effects. These findings illustrate the sensitivity of host plants to relatively small changes in suppressor dosage and have implications for those interested in enhancing silencing phenotypes in tobacco and other species through VIGS.

Optimization and Utilization of <em>Agrobacterium</em>-mediated Transient Protein Production in <em>Nicotiana</em>

“…To positively affect protein production, silencing suppressors may need to be specifically selected to be effective for the targeted plant species and viral vector 63 . TMV helicase has a suppressor of RNA silencing activity 64,65 . Our data confirm this observation as co-infiltration of p23 or p19 with pBID4-HAC1 resulted in no increase in GFP or a slight increase in the transient HAC1 protein production.…”

Influence of Host Chloroplast Proteins on Tobacco mosaic virus Accumulation and Intercellular Movement

“…Nicotiana tabacum and Nicotiana benthamiana were grown as described (Harries et al, 2008). Purified virus (TMV) U1 strain, (Shintaku et al, 1996)] or virus from plant extracts TVCV, CMV, and PVX (Yang et al, 2004) were used in some studies.…”

Resources for Virus-Induced Gene Silencing in the Grasses

“…It was recently shown that the tobacco mosaic virus 126-kD protein suppressor expressed as a transgene in N. benthamiana allowed a stronger silencing phenotype when expressed at a low level versus either a high level or in its absence (Harries et al, 2008). It was hypothesized that the suppressor expressed at a low level allowed a higher level of the virally encoded host gene transcript to be targeted by the silencing system.…”