Studies on the C-terminus of the Cowpea mosaic virus movement protein

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.