Molecular Plant Pathology - Pathogen Profiles

Chlorovirus: a genus of Phycodnaviridae that infects certain chlorella-like green algae

Ming Kang¹, David D. Dunigan¹² and James l. van Etten¹²

¹ Department of Plant Pathology and ² Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE 68583-0722, USA

Taxonomy:  

Chlorella viruses are assigned to the family Phycodnaviridae, genus Chlorovirus, and are divided into three species: Chlorella NC64A viruses, Chlorella Pbi viruses and Hydra viridis Chlorella viruses. Chlorella viruses are large, icosahedral, plaque-forming, dsDNA viruses that infect certain unicellular, chlorella-like green algae. The type member is Paramecium bursaria chlorella virus 1 (PBCV-1).

Chlorella virus particles are large (molecular weight ~1 x 10⁹ Da) and complex. The virion of PBCV-1 contains more than 100 different proteins; the major capsid protein, Vp54, comprises ~40% of the virus protein. Cryoelectron microscopy and three-dimensional image reconstruction of PBCV-1 virions indicate that the outer glycoprotein-containing capsid shell is icosahedral and surrounds a lipid bilayered membrane. The diameter of the viral capsid ranges from 1650 Å along the two- and three-fold axes to 1900 Å along the five-fold axis. The virus contains 5040 copies of Vp54, and the triangulation number is 169. The PBCV-1 genome is a linear, 330 744-bp, non-permuted dsDNA with covalently closed hairpin ends. The PBCV-1 genome contains ~375 protein-encoding genes and 11 tRNA genes. About 50% of the protein-encoding genes match proteins in the databases.

Cryoelectron microscopy and three-dimensional reconstruction of PBCV-1 virion

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