Evolution and origins of tobamoviruses

More than a dozen tobamoviruses are known. In nature, each species probably survives by moving between several closely related host species. Each infe cted plant contains a population of variants, but in most host populations the tobamovirus population is stable. The phylogenetic relationships of tob amovirus species broadly correlate with those of their angiosperm hosts. Th e simplest explanation for this correlation is that they have coevolved wit h the angiosperms, and hence, like them, are about 120-140 million years ol d. Gene sequence differences between species also indicate that the tobamov iruses are an ancient genus. Their gene sequences, and the protein motifs t hey encode, link them to tobraviruses, hordeiviruses and soil-borne wheat m osaic virus, more distantly to the tricornaviruses, and even to hepatitis v irus E and other furoviruses, rubiviruses and alphaviruses. Their progenito rs may have been associated with charophycean algae, and perhaps also plasm odiophoromycete fungi.