Cryo-EM structure reveals cylindrical nucleocapsids from two polydnaviruses

Arch Virol. 2018 Dec;163(12):3357-3363. doi: 10.1007/s00705-018-3958-8. Epub 2018 Sep 1.

Abstract

Bracovirus is one of the two polydnavirus genera. Here, we used a cryo-EM analysis to reveal the near-native morphology of two nucleocapsid-containing model bracoviruses: Microplitis bicoloratus bracovirus (MbBV) and Microplitis mediator bracovirus (MmBV). MbBV and MmBV nucleocapsids have discernable cap structures in two distal regions with relatively high electron density. Adjacent to the end-cap structures are two electron-lucent rings. Some nucleocapsids were uniformly electron-dense and had a distinctive "helix-tail-like structure". Cryo-EM revealed inconsistent nucleocapsid diameters of 34-69.9 nm in MbBV and 46-69.9 nm in MmBV, and the largest observed cylindrical area length was expanded to 126 nm.

MeSH terms

  • Animals
  • Cryoelectron Microscopy
  • Nucleocapsid / chemistry
  • Nucleocapsid / isolation & purification
  • Nucleocapsid / ultrastructure*
  • Polydnaviridae / chemistry
  • Polydnaviridae / ultrastructure*
  • Virion / chemistry
  • Virion / isolation & purification
  • Virion / ultrastructure
  • Wasps / virology*