Flies and birds share flight-specific gene use

With all the changes between the LCA of flies and chicks the same genes are specifically used, in the same way, to set up wing anatomy. God or unbelievably convegent evotution. It is the detailed genetics of wings that is the same, not just 'limbness'. I thought we might start seeing this from genomes and evo-devo work.The point is that the LCA of flies and chicks did not fly! Chicks supposedly evolved from reptiles and amphibians well after the LCA of flies and vertebrates.From Shubin NH (2002) Journal of Morphology 252, 15-28Abstract: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list _uids=11921033&dopt=Abstract
PDF (need subscription?): http://www3.interscience.wiley.com/cgi-bin/fulltext?ID=90011061&PLACEBO=IE.pdf

quote:

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Major groups are not assembled in a simple linear or
progressive manner new features are often cut
and pasted on different groups at different times. . .

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The assembly of limbs over developmental and
evolutionary time offers examples of the major processes
at work in the origin of novelties.

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Homologous genes, either orthologs or paralogs, are involved
with patterning the three ordinate axes of the wings
of Drosophila and chicks (Shubin et al., 1997; Tabin
et al., 1999). These genetic similarities extend to
more than gene sequence, structure or expression:
there appears to be functional conservation in the
specification of the anteroposterior, proximodistal,
and dorsoventral axes as well. Anteroposterior signaling
in both systems depends on a hedgehog/Shh,
dpp/BMP-2 signaling system (Lee et al., 1992; Ta-bata
et al., 1992; Basler and Struhl, 1994; Krauss et
al., 1993; Riddle et al., 1993).

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[This message has been edited by Tranquility Base, 07-08-2002]

WehappyWhat you've said sounds right but isn't actually completely true.Of course Hox/Hedghog etc are reused for non-wing limbs but it is the way they are used for wings that is the surprise. They are used in the same way for both very different wings. You'll notice I was careful in my above post and the title of the thread to take this subtlety into account.Take a look here. http://www.press.uchicago.edu/books/gee/shubin6.htmlIt is clear that the bird and fly wings are not homologous and yet have the similarities pointed out in my first post:

quote:

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The limbs of these taxa are not homologous as appendages because phylogenetically intermediate groups do not possess comparable structures. This suggests at least two phylogenetic possibilities: either similar genetic circuits were convergently recruited to make the limbs of different taxa, or these signalling and regulatory systems are ancient and patterned a different structure (presumably another type of outgrowth) in the common ancestor of protostomes and deuterostomes.

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For some reason the fly and the bird used these genes in exactly the same way even though nothing in between had wings.PS - your also wrong about my lack of interest in evo-devo.

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[This message has been edited by Tranquility Base, 07-09-2002]

PeterIf I have got it right, the use of these genes in such a specific manner would be highly unlikely for the evolutionary model.The key point is whether these genes are also used this way for non-wing limbs but my reading indicates this is not the point made in the ref cited. Convergent evolution of the shape of a bone or tissue is one thing, but, at some point, the convergent use of genes in a very specific manner becomes evidence of design.

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[This message has been edited by Tranquility Base, 07-09-2002]

^
My quotes came from the body of the article. I had access to the pdf but now Wiley wont let me be get back to it! My instituion has access to it so I will have to report this as a bug. I'm convinced the aspects are peculiar to wings (although I agree the genes aren't necessarily all unique to wings as pointed out by Wehappy) but we'll see.In any case the LCA of birds and insects did not have homologous limbs as stated in my second post web link to a mainstream collection of essays. Since that LCA the genes have been recruited in a parallel manner independently in the same way. I think the article strongly implies that this is even the case for flight specific use of these genes but I'll try and regain access to that pdf.

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[This message has been edited by Tranquility Base, 07-09-2002]

Wehappy, thankyou for going over all this in detail. I will get more int othis too as time permits.Let me just say this:The LCA of birds and flies did not have homologous limbs - is that correct? The web site does say this in plain English. What sort of creature (in plain English) was this LCA (asks TB who never did high school biology)?It is amazing then that birds and flies are using these genes in the same way in limbs.I still read Shubin that the use of these genes is flight specific but I agree it is hard to ascertain this 100% becasue he doesn't say it in plain English. His writing implies it strongly! If it was not flight specific surely he would cite similar results in mouse legs or something.

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[This message has been edited by Tranquility Base, 07-11-2002]