Cryo-Electron Microscopy Structure of theMacrobrachium rosenbergiiNodavirus Capsid at 7 Angstroms Resolution

Abstract

White tail disease in the giant freshwater prawn Macrobrachium rosenbergii causes significant economic losses in shrimp farms and hatcheries and poses a threat to food-security in many developing countries. Outbreaks of Macrobrachium rosenbergii nodavirus (MrNV), the causative agent of white tail disease (WTD) are associated with up to 100% mortality rates. Recombinant expression of the capsid protein of MrNV in insect cells leads to the production of VLPs closely resembling the native virus. We have investigated the structure of MrNV VLPs by cryogenic electron microscopy, determining a structure of the viral capsid at 7 angstroms resolution. Our data show that MrNV VLPs package nucleic acids in a manner reminiscent of other known nodavirus structures. The structure of the capsid however shows striking differences from insect and fish infecting nodaviruses, which have been shown to assemble trimer-clustered T=3 icosahedral virus particles. MrNV particles have pronounced dimeric blade-shaped spikes extending up to 6 nm from the outer surface of the capsid shell.Our structural analysis supports the assertion that MrNV along with the related virus of marine shrimp Penaeus vannamei nodavirus (PvNV) may represent a new genus of the Nodaviridae.

Molecular biology of Macrobrachium rosenbergii nodavirus infection in giant freshwater prawn

“…However, even though phylogenetic analysis of the Mr NV capsid affiliates Mr NV to betanodavirus (Bonami & Widada, ), but the secondary structure analysis of Mr NV capsid was found to be highly homolog with cucumber necrosis virus subunit, rather than nodaviruses (Somrit et al., ). Moreover, the recently published cryo‐electron microscopy structure of the Mr NV is reported to have a noteworthy difference in the viral capsid protein from the insect‐ and fish‐infecting nodaviruses (Ho, Kueh, Beh, Tan, & Bhella, ), which further strengthens the assertion of Mr NV as a member of new genus to Nodaviridae . This unique morphology of thin blade‐like dimeric P‐domains of the capsid protein resolved from the cryo‐electron microscopy data was claimed to be critically involved in the virus attachment, which required further comprehensive analysis.…”