viruses, evolution, and net traffic

[Ed Rybicki]

> From:          Leonard Pattenden <ddlpatte at mailbox.uq.edu.au>
> Subject:       Re: viruses, evolution, and net traffic

> My understanding of Viral evolution - as a protein chemist working in HIV
> - is that viruses are escaped genes. Thus - for example - in many
> retroviruses we see the aspartyl protease which cleaves the GAG-POL 
polyprotein
..
> smaller homodimeric protease we see today. The implication of my beliefs
> to your suggestions, is that propensities for particular viral types must
> reflect the availability of the machinery within the cell. Ie if a plant
> cell can produce reverse transcriptase which could be incorporated
> somehow into a virus, then the feasability of an RNA virus is

Okayeeee...first problem: not all viruses can be boxed with 
retroviruses as "escaped genes", at least, not as RECENTLY escaped 
genes.  In fact, there are no classical retroviruses (except maybe 
some retrotransposons which turn out to be infectious) in plants; 
only pararetroviruses of presumably ancient lineages (in that ALL 
retroviruses look MUCH more like each other than badna- and 
caulimoviruses look like each other).

Second problem: you will find some mammal-infecting viruses in the 
same superfamilies (based on polymerase homologies) as plant 
viruses...seeing as land plants and mammals diverged some 10exp9 
years ago...see what I mean?

                     Ed Rybicki, PhD  
      Dept Microbiology     |   ed at molbiol.uct.ac.za   
   University of Cape Town  | rybicki at uctvms.uct.ac.za
   Private Bag, Rondebosch  |  phone: x27-21-650-3265
      7700, South Africa    |   fax: x27-21-689 7573
    WWW URL: http://www.uct.ac.za/microbiology/ed.html      
                                        
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