Picorna-like viruses

Ed Rybicki ED at micro.uct.ac.za
Wed Jul 7 04:41:42 EST 1993


> From:          biocukm at okway.okstate.edu
> Subject:       RE: Picorna-like viruses
>
>  Ed Rybicki replied to my correction of his posting musing about picorna-
like
> virus evolution:
>
>|Related, yes - closely related, no...in fact, only marginally closer than
>|potyvirus sequences.  What I was trying to get at (and missed, by

>   (more stuff deleted)
>
> I appreciate the clarification and agree that it is interesting that the
plant
> picorna-like viruses as a group are so distant from the animal
picornaviruses.
> The question then is:  did the two groups really diverge from one
another way
> back in evolutionary time, or are we looking primarily at the changes
needed to
> adapt plant viruses to life (?) in animals, or vice versa (adaptation of
animal
> viruses to the plant niche)?

I have a partiality towards the idea - also mooted by Rob Goldbach - that
picornaviruses proper originated in insects, and got from there
into plants and animals: this idea has a lot going for it, when you
consider that insects are ancient (predate both angiosperms and mammals),
and feed off/on both plants and mammals, and that insect picornaviruses
are demonstrably more variable than are the mammalian
viruses.  The reason the plant picornaviruses are so diverged is that
plants are older than mammals, so the viruses have had longer to diverge.
Of course, this does not explain the picornaLIKE viruses (like
potyviruses, sobemoviruses), which are nearly all in plants....  Maybe the
original idea of using a single long ORF - and the original Vpg-dependent
polymerase - came from plants, but the picornavirus organisation proper
occurred in insects, then diverged to give us the different "more" picorna-
like insect viruses (such as nodaviruses), plant viruses (such as
comoviruses), and picornaviruses proper, which got into plants first, and
later into mammals.  A tangled evolutionary web, but fascinating for
phylogeny wonks like me....


  ____________________________________________________________________
 | Ed Rybicki, PhD             |       "Lord, won't you buy me        |
 | (ed at micro.uct.ac.za)        |                                      |
 | Dept Microbiology           |         A Mer-ce-des Benz..."        |
 | University of Cape Town     |                                      |
 | Private Bag, Rondebosch     |                                      |
 | 7700, South Africa          |           - Janis Joplin             |
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