Several of the proteins found associated with CYDV-RPV have well-described functions in nuclei, for example SMC1, SMC3 [67] , and NAP [68] . Luteovirids are positive-sense, single stranded RNA viruses. Although the coat protein and the RTP of the related luteovirid PLRV can localize to the nucleolar compartment of plant cell nuclei, this localization is lost in the presence of replicating vRNA [69] . Furthermore, in the early stages of infection of oats with BYDV, infected cell nuclei become morphologically distorted and filaments associated with cytoplasmic virions appear in the nucleoplasm and in nuclear pores [62] . Thus, a physical interaction between coat protein and these proteins, in vivo, is an intriguing possibility. However, the latter three proteins have been reported to have additional, non-nuclear functions and/or localization [70, 71, 72] . Furthermore, aphid SMC proteins are commonly found associating with purified PLRV in co-immunoprecipitation studies (Cilia, unpublished) . It is also possible that maturation of phloem sieve elements may release these proteins into the sap and provide a mechanism for functional protein interactions with luteovirids, or that these proteins are transported into the phloem sap to carry out functions yet to be defined. A detailed LC-MS/MS analysis of the pumpkin phloem sap proteome revealed numerous ribosomal proteins and homologues to NAP and many other proteins with nuclear functions [26] .