A Single Amino Acid Position in the Helper Component of Cauliflower Mosaic Virus Can Change the Spectrum of Transmitting Vector Species

Spanish National Research Council, Madrid, Madrid, Spain
Journal of Virology (Impact Factor: 4.44). 12/2005; 79(21):13587-93. DOI: 10.1128/JVI.79.21.13587-13593.2005
Source: PubMed


Viruses frequently use insect vectors to effect rapid spread through host populations. In plant viruses, vector transmission is the major mode of transmission, used by nearly 80% of species described to date. Despite the importance of this phenomenon in epidemiology, the specificity of the virus-vector relationship is poorly understood at both the molecular and the evolutionary level, and very limited data are available on the precise viral protein motifs that control specificity. Here, using the aphid-transmitted Cauliflower mosaic virus (CaMV) as a biological model, we confirm that the "noncirculative" mode of transmission dominant in plant viruses (designated "mechanical vector transmission" in animal viruses) involves extremely specific virus-vector recognition, and we identify an amino acid position in the "helper component" (HC) protein of CaMV involved in such recognition. Site-directed mutagenesis revealed that changing the residue at this position can differentially affect transmission rates obtained with various aphid species, thus modifying the spectrum of vector species for CaMV. Most interestingly, in a virus line transmitted by a single vector species, we observed the rapid appearance of a spontaneous mutant specifically losing its transmissibility by another aphid species. Hence, in addition to the first identification of an HC motif directly involved in specific vector recognition, we demonstrate that change of a virus to a different vector species requires only a single mutation and can occur rapidly and spontaneously.

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    • "Third, a mutant P2:GFP with a Q to Y substitution at amino acid 6 in P2 (P2Rev5:GFP) did not bind to vector aphid stylets. This mutation had previously been shown to disable the biological activity of P2, rendering it unable to support CaMV aphid transmission (Moreno et al., 2005). Most important, the fluorescence for P2:GFP was not randomly distributed, or scattered along the stylets, but was localized to a unique and tiny region at the aphid stylet tip (Uzest et al., 2007). "
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    • "A limiting factor in this approach has been the limited availability of atomic structures for the virions and proteins of interest. For example, elegant studies have identified essential regions of helper components of potyviruses and Cauliflower mosaic virus (Moreno et al., 2005; Syller, 2005), but structural information on these viruses is only available in low resolution models. Modeling studies of the structure of geminiviruses have resulted in predictions of the capsid protein structure based on cryoelectron microscopic reconstructions (Bottcher et al., 2004; Zhang et al., 2001). "
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    • "In this study, we used the aphid M. persicae to quantify CaMV transmission . This aphid is one of the two main vectors of CaMV in the field (Broadbent 1957; Kennedy et al. 1962; Moreno et al. 2005). Moreover, M. persicae has a worldwide distribution (Blackman and Eastop 2000) such that all viral isolates used in our study have potentially encountered this aphid vector. "
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