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Title: Point mutations in the potato leafroll virus major capsid protein alter virion stability and aphid transmission

item Gray, Stewart

Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2007
Publication Date: 6/1/2007
Citation: Kaplan, I.`., Lee, L., Ripoli, D., Palukaitis, P., Gildow, F., Gray, S.M. 2007. Point mutations in the potato leafroll virus major capsid protein alter virion stability and aphid transmission. Journal of General Virology. 88:1821-1830.

Interpretive Summary: Potato leafroll virus causes significant yield loss in the potato crop worldwide and reduces the value and availability of certified seed potatoes. The protein coat of potato leafroll virus is responsible not only for protecting the virus genetic material, but it also controls the ability of the virus to be transmitted by insects from plant to plant, and aids in the ability of the virus to infect various plant hosts. Our research is aimed at understanding how the virus protein interacts with plant hosts and insect vectors. In this paper we identify specific regions of the virus coat protein that affect virus transmission by insects, virus movement in plant hosts, and the ability of the virus to assemble stable particles. These regions of the protein are potential targets for novel disease control strategies that would prevent the virus from completing a normal life cycle.

Technical Abstract: The coat protein (CP) of potato leafroll virus (PLRV) is the primary component of the capsid and is a multifunctional protein known to be involved in vector transmission and virus movement within plant hosts, in addition to particle assembly. Thirteen mutations were generated in various regions of the CP and tested for their ability to affect virus-host and virus-vector interactions. Nine of the mutations prevented the assembly of stable virions. These mutants were unable to infect systemically four different host species. Furthermore, although virus replication and translation of CP were similar to wild type virus in individual plant cells, the translation of the coat protein readthrough product was reduced. Four of the mutants were able to assemble stable particles and infect systemically host plants similar to wild type virus, however, two of the mutants were transmitted less efficiently by aphid vectors. Based on a computer generated model of the PLRV CP, the mutations that prevented virion assembly were associated with subunit interfaces, while the amino acid alterations in the assembly competent mutants were associated with surface loops. This and previous work indicates the CP structural model has value in predicting the structural architecture of the virion.