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Author
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Topic: Are type III virulence systems really derived?
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Nel
Member
Member # 614
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posted 25. August 2003 19:11
Nic writes:
quote:
(And by the way, are you now saying that diseases using type III secretion were IDed? That is the implication of your statements. Perhaps the Bubonic Plague really was due to the wrath of God?)
I think the situation is that original uses were different. (Probably used as a mechanism for sex). By the way, I really like how you respect other people's opinions. It inspires me. Despite the fact that I regard a lot of what you say as either nonsensical or completely outlandish, I continue to take what you say seriously and analyze it accordingly. I don't see you doing the same.
[ 25. August 2003, 19:23: Message edited by: Nelson-Alonso ]
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Mike Gene
Member
Member # 149
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posted 25. August 2003 21:20
Nic: However, probably the most important point in favor of the flagella-->TTSS hypothesis was that TTSS sequences nested within flagellar sequences (That was my impression at least, Gophna et al. say that Nguyen et al's data never supported that idea). But that has been called into question.
If TTSS sequences nested within flagellar sequence, that would not merely be an important point. Seen in the context of all the other arguments, such a finding would essentially establish the flagella--> TTSS hypothesis. The problem is that the hypothesis of flagella --> TTSS doesn’t really predict such nesting (if you think about it). And the Gophna argument is built entirely around this questionable expectation.
The Gophna paper contains many weak arguments and I will be surprised if Nguyen, Kim, Hueck, or Macnab doesn’t swat this down. Regardless, it should make for a juicy TeleoLogic essay. ![[Smile]](smile.gif)
Keep in mind that, in many ways, I would be quite pleased if Gophna et. al were correct. They postulate some kind of original versatile export apparatus (which would still be significantly IC) that independently spawned the flagellum and TTSS. If this is true, we have a truly uncanny example of convergent evolution, as the similarities between the two systems extend well beyond the nine structural components. For just one example, consider the parallels between flgM and lcrQ, where structural integrity feeds back on transcriptional regulation (in identical fashion). I would consider this is very good example of front-loading.
Nic: (And by the way, are you now saying that diseases using type III secretion were IDed? That is the implication of your statements. Perhaps the Bubonic Plague really was due to the wrath of God?)
I thought I answered this type of argument years ago. Perhaps I’ll start a new thread on this one (before betting back to the eukaryotic flagellum).
[ 25. August 2003, 21:22: Message edited by: Mike Gene ]
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yersinia
Member
Member # 324
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posted 25. August 2003 21:49
Nelson writes of TTSS that he thinks the original uses were different. That's fine, if he allows evolutionists the same leeway and doesn't call such reasonable suggestions "fuzz".
(Nelson, I'm not trying to disrespect you, just trying to point out self-contradictions and inconsistencies in your statements)
(Mike, I'm aware of your views on TTSS, I raised the point only because Nelson was making the illegitimate "if HGT was involved I'll call it designed" argument)
Regarding the sequences-don't-nest issue, that's fine, Mike, if you want to hypothesize e.g. more rapid evolution of sequences (under conditions of parasitism, HGT, functional change, etc., all of which have precendent). If you think about the relative dating (3 billion years of flagellar divergence, <1 billion of TTSS divergence), I think nesting would be a decent default assumption if TTSS are derived, but the above factors could change things substantially. Just remember to allow us evolutionists similar leeway when we invoke such things...I recall you getting hung up on the tubulin-ftsZ divergence for example, where you were far less amenable to allowing explanations of the increase in the rate of sequence divergence.
I'm off on vacation for awhile, see ya...
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Nel
Member
Member # 614
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posted 26. August 2003 16:52
Nic writes:
quote:
Nelson writes of TTSS that he thinks the original uses were different. That's fine, if he allows evolutionists the same leeway and doesn't call such reasonable suggestions "fuzz".
There is a big difference. I'm not thinking up simpler precursors for very complex systems.
Nic writes:
quote:
Mike, I'm aware of your views on TTSS, I raised the point only because Nelson was making the illegitimate "if HGT was involved I'll call it designed" argument
How is it illegitimate?
[ 26. August 2003, 16:53: Message edited by: Nelson-Alonso ]
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