Submitted to: American Society for Virology Meeting
Publication Type: Abstract only
Publication Acceptance Date: 7/12/2002
Publication Date: 7/21/2003
Citation: Liang, D., Lee, L., Smith, D., Palukaitis, P., Gray, S.M. 2003. Biological analysis of potato leafroll virus structural proteins. American Society for Virology Meeting. p.17. Interpretive Summary:
Technical Abstract: Potato leafroll virus (PLRV) is phloem-restricted and is transmitted by aphids in a circulative persistent manner. The termination codon of the gene encoding the coat protein (CP) can be suppressed to allow translation of the readthrough domain (RTD). Within the CP gene is an open reading frame (ORF) encoding a movement protein (P17) in a different ORF. These 3 proteins function in virion assembly, aphid transmission, and cell-to-cell and long distant movement. However, their exact roles in host and vector specificity remain unknown. To examine this, two approaches were used. First, we constructed 3 mutant PLRV clones: DCP, DP17 and DRTD, in which expression of the CP, P17, and RTD respectively, was knocked out. DP17 and DRTD could systemically infect Nicotiana benthamiana following agroinoculation. By contrast, DCP, in which the stop codon for the CP gene was deleted and thus the mutant only expressed the CP-RTD fusion protein, accumulated only in the agroinoculated leaves. Western blotting results showed that DCP expressed only CP-RTD fusion protein but not CP alone. These results demonstrated that PLRV CP but not CP-RTD fusion or P17 is essential for long distant movement in N. benthamiana. In the second approach, three PLRV chimeric clones were constructed in which the ORFs encoding the CP-RTD, CP, and RTD were replaced with the corresponding ORFs of Cereal yellow dwarf virus (CYDV-RPV). All 3 clones were able to replicate and express their corresponding CP in agroinoculated N. benthamiana leaves. Furthermore, all 3 chimeric viruses could infect N. benthamiana systemically. These results suggest that RPV CP is able to package PLRV genomic RNA and assist its systemic movement in N. benthamiana. This supports the close phylogenic relationship between PLRV and RPV although no common host or aphid vector for both viruses has been found.