Which are the largest plant and animal virus?

The discovery of the Mimivirus in 2003 by Didier Raoult and Jean-Michel Claverie made headlines because of the virus remarkable size--comparable to that of many small bacteria. The pair's new analysis of the Mimivirus genome reveals even more surprises. The DNA contains some 1260 genes, 50 of which code for functions never before seen in viruses, including DNA repair and translating mRNA into protein. Viruses are generally considered nonliving because of their small size, simplicity, and inability to replicate outside of a host cell. They're just small packets of genetic material surrounded by a protein coating. But Claverie, a geneticist at Le Centre National de la Recherche Scientifique (CNRS) Structural and Genomic Information Laboratory in Marseille, France, believes that the Mimivirus's complexity should make researchers rethink their characterization of viruses as nonliving. The Mimivirus may once have replicated on its own but later lost that ability, Claverie says. But the virus still contains much of the machinery for self replication, a fact that Claverie believes makes them a type of living organism.

The Mimivirus genome, 1.2-Mb, may also help explain how complex life emerged. After comparing the sequence to those of a variety of other organisms, the researchers concluded that the Mimivirus lineage dates back some 3.3 billion years to the separation of early life into three major divisions: archaea, bacteria, and the more complex eukaryotes. Other scientists, noting the similarities between large DNA viruses and the cell nucleus that houses the genetic material in eukaryotes, have hypothesized that the nucleus may have originated when simple cells merged with viruses. Claverie says the findings fit with the idea that a large virus, perhaps similar to the Mimivirus, may have been the first to jump into a cell: The timing seems to fit, and the similarity between Mimivirus and eukaryotic genes involved in making proteins bolsters the hypothesis, he says.

Largest Known Animal

Among animal viruses, the pox virus family is one of the largest, based on genomic DNA size. This includes the viruses that cause smallpox, cowpox, rabbitpox, etc. Their genomes are over 120,000 base pairs of DNA long. They encode many of their own enzymes, tRNAs, and a host of other gene products. If you are looking for the actual molecular dimensions of the viral particle itself I am afraid that I can not answer that.

tobacco mosaic virus : plant

adeno virus : animal

another answer

The Potyviridae are the largest single taxonomic group of plant viruses

Determined nucleic acid sequence of ASF DNA genome. This is the largest animal virus yet sequenced.

Well the Dutch Elm disease killed just about every elm tree in the world. Then there was some kind of disease that killed off all of the American chestnut trees.