Related Experiment Videos
Studies on the C-terminus of the Cowpea mosaic virus movement protein
P Bertens1, W Heijne, N van der Wel
1Laboratory of Molecular Biology, Wageningen University, Wageningen, The Netherlands.
Abstract:
Cowpea mosaic virus (CPMV) spreads from cell-to-cell as virus particles through tubular structures in modified plasmodesmata which are composed of viral movement protein (MP). Mutational analysis of the MP has revealed that the N-terminal and central regions of the MP are involved in tubule formation and that the C-terminal domain probably has a role in the interactions with virus particles. By constructing C-terminal deletion mutants and comoviral hybrid MPs, it was possible to delineate the C-terminal border of the tubule-forming domain to a small region between amino acids 292 and 298. Experiments with tripartite viruses in protoplasts indicated that the C-terminus of the MP is involved in the incorporation of virus particles in the tubule and that for efficient incorporation of virus particles all MP molecules incorporated in a tubule need to contain a functional C-terminus. A mutant virus coding for a MP in which the last 10 C-terminal amino acids were replaced by the green fluorescent protein (GFP) was able to form tubules in protoplasts. These tubules did not contain virus particles, probably because the GFP interferes with the incorporation of virions into the tubule. These results suggest a model for the structure of the tubule in which the C-terminus of the MP is located inside the tubular structure, where it is able to interact with virus particles.
Insights
Cowpea mosaic virus movement protein (MP) forms tubules for cell-to-cell spread. The MP
Area of Science:
- Plant virology
- Molecular biology
- Cell biology
Background:
- Cowpea mosaic virus (CPMV) utilizes modified plasmodesmata for intercellular transport.
- Viral movement protein (MP) is essential for forming tubular structures that facilitate virus spread.
Purpose of the Study:
- To delineate the functional domains of the CPMV movement protein (MP) involved in tubule formation and virus particle interaction.
- To elucidate the role of the MP C-terminus in incorporating virus particles into plasmodesmatal tubules.
Main Methods:
- Site-directed mutagenesis of the CPMV MP to create deletion mutants.
- Construction of comoviral hybrid MPs.
- Infection of plant protoplasts with wild-type and mutant viruses.
- Analysis of tubule formation and virus particle incorporation using microscopy.
Main Results:
- The N-terminal and central regions of the MP are crucial for tubule formation.
- The C-terminal domain of the MP is critical for interacting with and incorporating virus particles into tubules.
- A specific region between amino acids 292 and 298 defines the C-terminal border of the tubule-forming domain.
- Functional C-termini on all MP molecules within a tubule are necessary for efficient virus particle incorporation.
- Replacing the MP C-terminus with GFP resulted in tubules that did not contain virus particles.
Conclusions:
- The C-terminus of the CPMV MP plays a direct role in mediating virus particle incorporation into transport tubules.
- A model is proposed where the MP C-terminus is located internally within the tubule, facilitating virion binding.
- Understanding MP structure-function relationships is key to deciphering virus cell-to-cell movement mechanisms.