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Title: IDENTIFYING BIOLOGICALLY ACTIVE REGIONS OF THE POTATO LEAFROLL VIRUS COAT PROTEIN

Author
item Lee, Lawrence
item LIANG, DELIN - CORNELL UNIVERSITY
item PALUKAITIS, PETER - SCRI, SCOTLAND
item Gray, Stewart

Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2003
Publication Date: 7/21/2003
Citation: Lee, L., Liang, D., Palukaitis, P., Gray, S.M. 2003. Identifying biologically active regions of the potato leafroll virus coat protein. American Society for Virology Meeting. p. 27.

Interpretive Summary:

Technical Abstract: The Potato leafroll virus (PLRV) coat protein (CP) encoded by ORF 3 is one of two structural proteins. It is required for virion assembly, systemic infection of plants and aphid transmission. Specifically the CP regulates the movement of virus from the aphid gut into the haemocoel. Alanine-scanning mutagenesis was used to identify biologically active domains of the PLRV CP. Thirteen mutants were able to replicate and accumulate in agroinoculated Nicotiana clevelandii and N. benthamiana leaves. Two of these were unable to move out of the inoculated leaves and systemically infect both plant hosts. Both mutants accumulated lower levels of CP in the agroinoculated leaves of N. clevelandii, when compared to wild-type virus and immunocapture (IC)-RT-PCR suggested that virions are not assembled. Seven additional mutants were significantly impaired, in their ability to accumulate in agroinoculated and systemically infected tissues. Four of the seven eventually accumulated higher levels of virus though still lower than wild-type virus, but when progeny viruses were sequenced, they had reverted to wild-type PLRV sequence. Interestingly, the amino acids that reverted are associated with antigenic and/or putative virion surface domains that are highly conserved among poleroviruses. Three of the seven mutants accumulated to significantly lower levels in N. clevelandii and no reversion was observed. Interestingly, two of the three mutants did not systemically infect N. benthamiana. IC-RT-PCR suggested that virions are assembled in the agroinoculated leaves of N. clevelandii, but the virions may not be stable in the systemic leaves. Four of the thirteen mutants accumulated to wild-type levels in systemically infected tissues, but only two were transmitted by aphids after feeding on the infected leaves. The different phenotypes can be used to begin the identification of biologically active domains on the PLRV CP.