> From: biocukm at okway.okstate.edu (Ulrich Melcher)
> I think we (Lartey, Voss and myself, ms in preparation) may have
come across a
> case where convergent sequence evolution has occurred during the
evolution of
> the ribgrass mosaic virus subgroup of tobamoviruses. In their RNA
genomes the
> movement and coat protein cistrons overlap for 25 codons. In
other
> tobamoviruses there is no overlap or a shorter overlap. The
ancestral cistron
> in the overlap region can be deduced to be the coat protein one.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Er...why? Is it not possibly an N-terminal extension of the CP?
How "homologous" are those regions of the tobamovirus CPs? Enough
to say that this has not occurred?
...I think that is what is meant by convergent
> sequence evolution. The situation will certainly complicate
phylogenies based
> on movement protein amino acid sequences since all alignment
algorithms will put
> the C-termini together in some fashion, even though they are
encoded by non-
> homologous nucleotides.
This is definitely true IF it is the case...so, for all rules there
has to be an exception!
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