Cloning and subcellular localization of the phosphoprotein and nucleocapsid proteins of Potato yellow dwarf virus, type species of the genus Nucleorhabdovirus

We have cloned and characterized mRNAs corresponding to the phosphoprotein (P) and nucleocapsid (N) genes of the sanguinolenta strain of Potato yellow dwarf virus (PYDV). The P and N messenger RNAs both begin with a common AAACA pentanucleotide and are 1546 nt and 962 nt in length, and capable of encoding 52 kDa and 31 kDa proteins, respectively. The N mRNA contains a 12 nt 5′ non-translated sequence (NTS) and a 83 nt 3′-NTS. Similarly, the P mRNA has a 19 nt 5′-NTS and a 125 nt 3′-NTS. Primary structure analyses revealed three potential phosphorylation sites in the P protein and six in the N protein. Despite a lack of predictable nuclear localization signals (NLSs) in either protein, transient expression of the P and N proteins in N. benthamiana showed that both proteins are targeted exclusively to nuclei. Phylogenetic analyses showed that PYDV is most closely related to Maize mosaic virus and Taro vein chlorosis virus, which also lack predictable NLSs in their N proteins. The present data further distinguish PYDV from SYNV and suggest that, together, these viruses serve to provide a more comprehensive view of rhabdovirus cell biology, which can be studied in a common host plant.