Rubisco small subunit (RbCS) is co-opted by potyvirids as the scaffold protein in assembling a complex for viral...

Area of Science:

• Plant virology
• Molecular plant-pathology
• Cell biology

Background:

• Plant viruses, particularly Potyviridae (potyvirids), require movement through plasmodesmata (PD) for their life cycle.
• While some viral and host factors are known, the complete protein machinery for potyvirid cell-to-cell movement remains incompletely understood.

Purpose of the Study:

• To investigate the role of ANRSV HCPro2 in viral intercellular movement.
• To identify host and viral proteins interacting with HCPro2 and elucidate their function in potyvirid cell-to-cell transport.

Main Methods:

• Affinity purification coupled with mass spectrometry to identify HCPro2-interacting proteins.
• In planta co-immunoprecipitation assays to confirm protein-protein interactions.
• RNA interference (RNAi) to knock down host protein expression and assess its impact on viral movement.

Main Results:

• ANRSV HCPro2 was found to assist in viral intercellular movement, functionally complemented by HCPro from other potyviruses.
• HCPro2 interacts with viral proteins CI and CP, forming PD-localized complexes during infection.
• The host protein Nicotiana benthamiana-Rubisco small subunit (NbRbCS) mediates interactions between HCPro2, CI, and CP.
• Knockdown of NbRbCS significantly impaired these interactions and attenuated the movement of ANRSV and other potyvirids.

Conclusions:

• Potyvirids hijack the nucleus-encoded, chloroplast-targeted NbRbCS protein as a scaffold.
• This hijacking facilitates the assembly of a protein complex essential for viral movement across plant cells.
• NbRbCS is a critical host factor for the intercellular and systemic spread of multiple potyvirid species.