The interaction dynamics of two potato leafroll virus movement proteins affects their localization to the outer membranes of mitochondria and plastids

Authors: Deblasio, Stacy; XU, YI - Cornell University; JOHNSON, RICHARD - University Of Washington; REBELO, ANA RITA - Boyce Thompson Institute; MACCOSS, MICHAEL - University Of Washington; Gray, Stewart; Heck, Michelle

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2018
Publication Date: 10/26/2018
Citation: DeBlasio, S.L., Xu, Y., Johnson, R., Rebelo, A., MacCoss, M., Gray, S.M., Heck, M.L. 2018. The interaction dynamics of two potato leafroll virus movement proteins affects their localization to the outer membranes of mitochondria and plastids. Viruses. 10(11):585. https://doi.org/10.3390/v10110585.
DOI: https://doi.org/10.3390/v10110585

Interpretive Summary: No agricultural management strategies exist that block transmission of insect-borne plant viruses. Within plants, viruses move from cell to cell to achieve infection in the plant. This work revealed how two proteins from the Potato leafroll virus move within cells and then how the plant proteins regulate that movement. The research shows key viral-plant interactions that regulate how the virus moves from one plant cell to the next plant cell during infection. This data will enable scientists to develop novel forms of virus resistance in plants and new strategies to block insect transmission.

Technical Abstract: Potato leafroll virus (PLRV) is an agriculturally important, aphid-borne virus whose infection cycle is restricted to the vasculature of plants. Four viral proteins regulate movement of PLRV: the proteins making up the virus capsid (protein shell) and two non-structural proteins, P3a and P17. Very little is known about how these proteins interact with each other and the plant to coordinate movement of virus within and between plant cells. In our study, we performed a comprehensive analysis of the interaction dynamics and subcellular movements of P3a and P17. We used quantitative, affinity purification-mass spectrometry to show that P3a forms a complex with PLRV. Using mutant forms of PLRV, we were able to determine that this interaction does not require virion assembly but is dependent on the presence of P17. We show that P3a and P17 can directly interact in plant cells and that this association facilitates their localization to the outer membranes of mitochondria and chloroplasts. Trafficking of these organelles to the cell periphery brings these viral complexes in close proximity to plasmodesmata, channels that regulate movement of molecules and virus particles between cells. At these channels, we observed the dispersal of P17 towards chloroplasts in real-time. Our results support previous ultrastructural studies of PLRV infected phloem cells and suggest that the intracellular trafficking of PLRV P3a is more complex than what has previously been reported for other viruses in the same family and that the movement proteins of PLRV may work together to transport virus through multiple plant membranes to reach plasmodesmata.