Nuclear F-actin is required for AcMNPV nucleocapsid morphogenesis

Area of Science:

• Molecular Virology
• Cell Biology
• Insect Pathology

Background:

• Filamentous actin (F-actin) colocalizes with the major capsid protein of Autographa californica M nucleopolyhedrovirus (AcMNPV) during nucleocapsid assembly in infected lepidopteran host cells.
• Cytochalasin D (CD), an actin polymerization inhibitor, prevents the assembly of progeny AcMNPV, indicating a potential role for nuclear F-actin in viral morphogenesis.

Purpose of the Study:

• To investigate the essential role of nuclear F-actin in the morphogenesis of Autographa californica M nucleopolyhedrovirus (AcMNPV).
• To provide direct evidence for the necessity of F-actin in AcMNPV nucleocapsid assembly.

Main Methods:

• Utilized Cytochalasin D (CD) to disrupt actin filaments in infected lepidopteran host cells.
• Engineered two AcMNPV recombinants expressing either wild-type or CD-resistant actin at equivalent rates.
• Assessed the differential sensitivity of these recombinants to CD treatment.

Main Results:

• AcMNPV nucleocapsid assembly was observed to colocalize with F-actin within the nuclei of infected host cells.
• CD treatment significantly inhibited progeny AcMNPV assembly, confirming the importance of F-actin.
• AcMNPV recombinants expressing CD-resistant actin exhibited reduced sensitivity to CD compared to those with wild-type actin.

Conclusions:

• Nuclear F-actin is essential for the morphogenesis of Autographa californica M nucleopolyhedrovirus (AcMNPV) nucleocapsids.
• The dependence of AcMNPV on nuclear F-actin is a unique characteristic among intracellular pathogens.
• This F-actin requirement may function as a significant host range factor for AcMNPV.