Cauliflower mosaic virus P6 inclusion body formation: a dynamic and intricate process

Authors: VELAZQUEZ, ROBERTO - University Of Toledo; JACQUES, SARAH - University Of Toledo; MULLER, CLARE - University Of Toledo; Boldt, Jennifer; SCHOELZ, JAMES - University Of Missouri; LEISNER, SCOTT - University Of Toledo

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2020
Publication Date: 10/30/2020
Citation: Velazquez, R.A., Jacques, S., Muller, C., Boldt, J.K., Schoelz, J., Leisner, S. 2020. Cauliflower mosaic virus P6 inclusion body formation: a dynamic and intricate process. Virology. 553:9-22. https://doi.org/10.1016/j.virol.2020.10.003.
DOI: https://doi.org/10.1016/j.virol.2020.10.003

Interpretive Summary: Plant viruses impair plant growth and development, leading to reduced crop productivity. During the infection process, many viruses form specialized virus-induced compartments called inclusion bodies (IBs) in host plant cells. They use these IBs to generate the components necessary to spread to additional cells within the plant, furthering the severity of infection. Understanding IB formation will lead to the development of new targeted strategies that impede these “virus-producing factories”, putting them out of commission and reducing the severity of an infection. IBs can form a variety of sizes. The discovery that small IBs continually move around within a plant cell, likely hitching a ride on actin filaments as the filaments get longer, means that targeting the disruption of the actin cytoskeleton should stop IB movement, limit their size, and provide one mode of action for controlling an infection. Once IBs reach a certain size, they appear to exploit the host cell’s aggresome pathway for their own gain, particularly during later stage infection; this is the first report of the use of this pathway by plant viral IBs. This knowledge advances our understanding of plant viruses and is an important first step in generating new hypotheses for how to control virus infections. It provides new targets to consider when developing commercial products that effectively reduce virus infection severity, minimizing crop damage and yield loss.

Technical Abstract: During an infection, Cauliflower mosaic virus (CaMV) forms inclusion bodies (IBs) mainly composed of viral protein P6, where viral activities occur. Because viral processes occur in IBs, understanding the mechanisms by which they form is crucial. P6-GFP expressed in Nicotiana benthamiana leaves formed IBs of a variety of shapes and sizes. Small IBs were dynamic, undergoing fusion/dissociation events. Coexpression of actin-binding polypeptides with P6-GFP altered IB size distribution and inhibited movement. This suggests IB movement is required for fusion and growth. A P6 deletion mutant was discovered that formed a single large IB per cell, which suggests it exhibited altered fusion/dissociation dynamics. Myosin-inhibiting drugs did not affect small IB movement, while those inhibiting actin polymerization did. Large IBs colocalized with components of the aggresome pathway, while small ones generally did not. This suggests a possible involvement of the aggresome pathway in large IB formation.