A Host RNA Helicase-Like Protein, AtRH8, Interacts with the Potyviral Genome-Linked Protein, VPg, Associates with the Virus Accumulation Complex, and Is Essential for Infection

Abstract

The viral genome-linked protein, VPg, of potyviruses is a multifunctional protein involved in viral genome translation and replication. Previous studies have shown that both eukaryotic translation initiation factor 4E (eIF4E) and eIF4G or their respective isoforms from the eIF4F complex, which modulates the initiation of protein translation, selectively interact with VPg and are required for potyvirus infection. Here, we report the identification of two DEAD-box RNA helicase-like proteins, PpDDXL and AtRH8 from peach (Prunus persica) and Arabidopsis (Arabidopsis thaliana), respectively, both interacting with VPg. We show that AtRH8 is dispensable for plant growth and development but necessary for potyvirus infection. In potyvirus-infected Nicotiana benthamiana leaf tissues, AtRH8 colocalizes with the chloroplast-bound virus accumulation vesicles, suggesting a possible role of AtRH8 in viral genome translation and replication. Deletion analyses of AtRH8 have identified the VPg-binding region. Comparison of this region and the corresponding region of PpDDXL suggests that they are highly conserved and share the same secondary structure. Moreover, overexpression of the VPg-binding region from either AtRH8 or PpDDXL suppresses potyvirus accumulation in infected N. benthamiana leaf tissues. Taken together, these data demonstrate that AtRH8, interacting with VPg, is a host factor required for the potyvirus infection process and that both AtRH8 and PpDDXL may be manipulated for the development of genetic resistance against potyvirus infections.

Ribosomal Protein P0 Promotes Potato Virus A Infection and Functions in Viral Translation Together with VPg and eIF(iso)4E

“…Several potential translational components are associated with RCs of TuMV, including eIF(iso)4E, PABP, eEF1A, and AtRH8 (16)(17)(18)63), but their roles have remained elusive. They may function to regulate viral translation (64), as translation is coupled with replication (35) and RCs (65) during potyvirus infection.…”

A Plant Small Polypeptide Is a Novel Component of DNA-Binding Protein Phosphatase 1-Mediated Resistance to Plum pox virus in Arabidopsis

“…However, additional host components might be participating in the interaction with potyviruses, either promoting infection as susceptibility factors or mediating resistance. Only recently, some of these factors have been discovered, like a Cys-rich VPg-interacting protein of unknown function involved in potyvirus movement (Dunoyer et al, 2004), a DEAD box RNA helicase also interacting with VPg (Huang et al, 2010), heat shock protein HSP70 (Hafrén et al, 2010;Jungkunz et al, 2011), and proteasome components (Jin et al, 2007;Dielen et al, 2011), although the roles they play and the underlying mechanisms remain obscure in most cases. Another example is AtDBP1, whose function aids potyviruses like PPV and Turnip mosaic virus (TuMV) to successfully infect the plant, likely through its interaction with eIF(iso)4E (Castelló et al, 2010).…”

Detection, Understanding and Controlof Soybean Mosaic Virus

“…Silencing or mutation of host factors required for virus infection will generate genetic resistance to the virus. Over the last decade, a number of host factors required for potyvirus infection have been identified and examples include eIF4E, eIF(iso)4E, eIF4G, PABP, AtRH8 and PpDDX (Lellis et al, 2002;Ruffel et al, 2002Ruffel et al, , 2005Nicaise et al, 2003Nicaise et al, , 2007Gao et al, 2004;Kang et al, 2005;Decroocq et al, 2006;Bruun-Rasmussen et al, 2007;Dufresne et al, 2008;Huang et al, 2010). Recently Piron et al (2010) have reported a successful story about how to deploy host factors for the development of resistance to potyviruses in tomato.…”

“…The resulting resistance is often mediated by RNA silencing or posttranscriptional gene silencing (PTGS) which induces sequence-specific degradation of viral RNA (Waterhouse et al, 2001). But the RNA silencing-mediated resistance may be overcome in two scenarios (Huang et al, 2010), i.e., in mixed infections by a strong silencing suppressor from unrelated viruses (Mitter et al, 2001) or through mutations during virus replication by the viral RdRP that lacks proofreading activities (Kang et al, 2005b). To develop PDR against SMV, the CP and 3'-UTR region of the SMV N isolate (strain G2) was engineered into soybean .…”

“…These membranous vesicles have been proposed to provide a scaffold for anchoring the virus replication complex (VRC), confine the process of RNA replication to a specific safeguarded cytoplasmic location to prevent the activation of host defense responses, and to recruit the components required for replication and maintain the proper concentrations of these components (Wileman, 2006). The potyvirus VRC-containing vesicles seem to originate at endoplasmic reticulum exit sites (ERES), traffic along the microfilaments and target chloroplasts for replication (Wei et al, 2010). It has been shown that in potyvirus-infected plant cells, these vesicular compartments contain a number of host proteins, i.e., heat shock cognate 70-3 (Hsc70-3), poly(A)-binding protein (PABP), eEF1A and eIF(iso)4E, and several non-structural viral proteins, such as the 6K2, NIb (the viral RNA dependent RNA polymerase, RdRp), NIa (including NIa-VPg or NIa-Pro or as a precursor protein) and CI Thivierge et al, 2008;Cotton et al, 2009;Wei et al, 2010a).…”