Potato virus Y helper component protein is associated with amorphous inclusions

This study investigates the cellular location of the helper component (HC) protein of potato virus Y (PVY), a protein essential for aphid transmission of potyviruses. Researchers used immunoblotting and immunogold electron microscopy to examine HC protein distribution in infected tobacco plant tissues. Western blot analysis demonstrated that HC protein was present in leaf blades and veins but absent from petioles. Immunogold labeling revealed that HC protein localizes specifically to rod-shaped cytoplasmic inclusions within infected cells, categorized as amorphous inclusions. The specificity of these findings was confirmed by the absence of labeling when using preimmune serum and the lack of cross-reactivity with other potyvirus-infected tissues. These results provide direct evidence supporting earlier indirect suggestions that amorphous inclusion bodies serve as pools or reservoirs of HC protein in potyvirus-infected cells. The study confirms that different potyviruses produce morphologically distinct amorphous inclusions despite their functional similarities in HC protein sequestration.

Key findings

• PVY helper component protein is specifically localized within rod-shaped amorphous inclusions in infected plant cells
• HC protein is present in leaf blade and vein tissues but absent from leaf petioles of infected plants
• Immunogold labeling with anti-HC serum specifically marks amorphous inclusions while preimmune serum produces no labeling, confirming specificity
• The PVY HC antiserum does not cross-react with HC proteins from other potyviruses (TEV, TVMV), indicating serological distinctness
• Amorphous inclusions function as sites of HC protein accumulation and represent pools or reservoirs of this essential potyviral protein