LC-MS/MS enabled us to detect numerous host proteins copurifying with virion particles in the sucrose gradients. The SRM data indicate a complex picture on the roles of these plant proteins in luteovirid transmission by aphids. How might host proteins also participate in aphid transmission? As a result of natural selection, aphid acquisition of CYDV-RPV by aphids may have been favored from phloem cells with higher protein expression, a phenotype that could have evolved as a response from virus infection, the act of aphid feeding, or both in combination. Coingestion of soluble plant proteins that associate with virions may help stimulate endocytosis into the epithelial cells of the aphid HG in a host-dependent manner. These data are consistent with previous observations of host proteins as associated with insecttransmitted viruses [21, 22] and that addition of any soluble protein into the diet acquired together with virus can enhance transmission efficiency [22] . In tobacco BY-2 cells, sugar levels tightly regulate pyruvate dehydrogenase E1 and E2 promoters. Promoter activity is markedly increased by sugar depravation [55] . We detected pyruvate dehydrogenase E1 and E2 at increased levels in aphids fed on CYDV-RPV infected plants. In contrast, cellulose synthase was detected at similar levels in aphids fed on healthy or CYDV-RPV infected plants. This is consistent with a more general role for the latter protein in aphid-plant interactions that CYDV-RPV may exploit. In varieties of wheat that are susceptible to the phytotoxic Russian wheat aphid, Diuraphis noxia, the mRNA encoding for cellulose synthase is up-regulated 4 to7fold during aphid infestation [56] . Intriguingly though, evidence suggests that the Russian wheat aphid is a poor vector for yellow dwarf viruses [57, 58] . Cellulose synthase is a member of the glycosyltransferase family A protein family. These proteins synthesize glycoconjugates by transferring a sugar moiety to a donor molecule, such as a protein or lipid. Little is understood about the role of protein glycosylation in non-enveloped virusesspecifically plant viruses [59] and a role for glycosylation in luteovirid transmission is not well understood [59, 60] .