Cryo-Electron Microscopy and Image Analysis of Cauliflower Mosiac Virus

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The native three-dimensional structure of cauliflower mosaic virus (CaMV) will be studied using recently developed cryo-electron microscopy and image analysis techniques. CaMV is one of the most extensively studied plant viruses, in part, because it was the first plant virus in which a double-stranded DNA genome was discovered. However, little is known about the details of the organization and assembly of the DNA and protein components. The resulting structural model will provide new insights about the symmetry and packing arrangement of the protein subunits in the capsid and may reveal new details concerning protein-DNA interactions within the structure. CaMV is the type member of the caulimovirus family, the only group of plant viruses known to encapsidate a genome of double-stranded DNA. Caulimoviruses are unique among small DNA viruses of eukaryotes in being assembled in the cytoplasm rather than the nucleus of their host cells. They serve as a suitable model system for studying plant gene organization, expression and replication and they also are potentially useful as gene vectors for the genetic manipulation of higher plants. In addition, there are striking similarities between CaMV and certain animal viruses. For example, CaMV and the retroviruses both replicate by reverse transcription and this represents the first such example of this phenomenon in plant cells. To fully understand how CaMV functions, detailed knowledge of its structure is essential.