Content
⇒ 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.