nuclear pores in protists

Mark Siddall mes at zoo.toronto.edu
Wed Apr 13 18:54:18 EST 1994


In article <199404111612.JAA06280 at net.bio.net> CGE at CU.NIH.GOV writes:
>vstr18a at sfsuvax1.sfsu.edu (Kathleen Anderson) wrote:
>
>>Does anyone know of any protists who do not possess nuclear
>>pore complexes characteristic of Dictyostelium, yeasts, and
>>metazoans?
>
>I don't know of any that lack them but microsporidia and Giardia,
>which are representatives of two of the earliest branching
>eukaryotic lineages, both have nuclear pores. This would mean
>that protists lacking them would have to have lost them
>secondarily. As nuclear pores appear crucial for the movement
>of RNAs out of and proteins into the nucleus I think this unlikely.

In the first place: Giardia lamblia is NOT likely an early diverging
eukaryotic lineage!  (see: Siddall et al., 1992. "Phylogenetic analysis
of the Diplomonadida (Wenyon, 1926) Brugerolle, 1975: Evidence for 
heterochrony in protozoa and against Giardia lamblia as a "missing link".
J. Protozool. 39: 361-367.)

In the second place: diplomonads (to my knowledge) do have nucleopores.

In the third place:  lack of nuclear pores in other protists would not
be prima facie evidence of secondary loss, and would require a thorough
understanding of that protist's placement in a eukaryotic phylogeny, the
optimization of that and other characters etc etc etc...

So much for my $0.02 (CAN of course, which works out to about $0.014 US)

Mark

-- 
Mark Siddall             The greatest obstacle to discovery is not ignorance,
Department of Zoology       - it is the _illusion_ of knowledge.
University of Toronto                             D. J. Boorstein
mes at zoo.toronto.edu



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