⇒ Eukaryotic Viruses
⇒ Viral Structure
⇒ Animal Viruses
⇒ Oncogenic Viruses
⇒ Plant Viruses
While there are exceptions, the vast majority of plant viruses have a single-
stranded linear, +RNAgenome with a capsid having helical or icosahedral
symmetry. They have small genomes, encoding for only three to
four proteins: (1) a helicase; (2) an RNAreplicase; (3) a cell-to-cell movement
protein; and (4) a capsomere. The helicase is thought to be important
in the unwinding and separation of the plus and minus RNAstrands.
The replicase, an RNA-dependent RNA polymerase, is encoded in those
viruses that are able to use the host's enzymes. The cell-to-cell movement
protein facilitates the spread of the viral RNA through plant tissue. The
capsomere is the protein subunit of the capsid.