Crystal structure of the potato leafroll virus coat protein and implications for viral assembly

Authors: ADAMS, MYFANWY - Cornell University; SCHILTZ, CARL - Cornell University; Heck, Michelle; CHAPPIE, JOSH - Cornell University

Submitted to: Journal of Structural Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2021
Publication Date: 11/20/2021
Citation: Adams, M., Schiltz, C., Heck, M.L., Chappie, J. 2021. Crystal structure of the potato leafroll virus coat protein and implications for viral assembly. Journal of Structural Biology. 214(1):107811. https://doi.org/10.1016/j.jsb.2021.107811.
DOI: https://doi.org/10.1016/j.jsb.2021.107811

Interpretive Summary: Plant viral infection is responsible for billions of dollars of crop loss each year in the US and internationally. Poleroviruses, such as the potato leafroll virus, are transmitted by aphids, tiny sap sucking insects. Understanding viral assembly is critical for the development of new strategies to mitigate polerovirus transmission by aphids and subsequent crop loss. Research conducted by ARS scientists and university partners shows that crystallography is a viable approach to elucidate the structural geometry and symmetry interactions of poleroviruses. Insights from the crystal structure formed in vitro reported here provide support for the requirement of pentamers to close the icosahedral-shaped, outer shell of the virus. The viral icosahedral shell is necessary for the virus to move within a plant and to be transmitted by aphids. The potato leafroll virus crystal structure not only affords a high-resolution snapshot of viral shell but also shows potential intermediate stages of the assembly and folding of the shell. Future in vitro studies examining viral assembly and the effects of the viral genome will be necessary to define the exact mechanism and kinetics of virus maturation. The structural assemblies described and compared in this work will help in modeling these pathways.

Technical Abstract: Viruses of the Luteoviridae family are aphid-transmitted, agricultural pathogens that infect a wide array of staple food crops. Previous cryo-electron microscopy studies of virus-like particles indicate that luteovirid viral capsids are built from a structural coat protein that organizes with T=3 icosahedral symmetry. We present the crystal structure of a truncated version of the coat protein monomer from potato leafroll virus at 1.5-Å resolution. In the crystal lattice, monomers pack into flat sheets that preserve the two-fold and three-fold axes of icosahedral symmetry and show minimal structural deviations when compared to the full-length subunits of the assembled virus-like particle. These observations have important implications in viral assembly and maturation, suggesting that the CP N-terminus and its interactions with RNA serve as a key driver for generating capsid curvature.