How Does Horizontal Gene Transfer Shape the Tree of Life?

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Discussion Overview

The discussion centers on the impact of horizontal gene transfer on the evolutionary history of life, particularly in relation to the concept of a single root of life and the evolution of eukaryotes. Participants explore the implications of horizontal gene transfer for understanding common ancestry, the tree of life, and the potential for multiple origins of life.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that horizontal gene transfer complicates the traditional view of the evolutionary tree, suggesting that eukaryotes are a fusion of multiple branches rather than a separate lineage.
  • There is a discussion about the concept of a single root of life, with some arguing that while evidence supports a common ancestor, the possibility of multiple independent origins of life remains plausible.
  • Some participants mention that the last universal common ancestor (LUCA) may have retained genetic elements from extinct lineages through horizontal gene transfer, raising questions about the survival of multiple origins.
  • One participant notes that the conservation of neurotransmitters across species could indicate a deeper evolutionary connection, potentially supporting the idea of common descent.
  • There is a query about the term "karyota," with some participants seeking clarification on its use and distinction from "eukaryote." A later reply suggests it may be a term defined in a specific review article.
  • Some participants express uncertainty about the implications of horizontal gene transfer on the understanding of evolutionary history, particularly regarding the extinction of other life forms that may have existed alongside LUCA.

Areas of Agreement / Disagreement

Participants generally agree that horizontal gene transfer plays a significant role in evolution, but multiple competing views remain regarding the implications for the tree of life and the concept of a single root. The discussion remains unresolved on the extent to which multiple origins of life may have survived.

Contextual Notes

Some claims rely on specific definitions and assumptions about genetic transfer and common ancestry, which may not be universally accepted. The discussion also highlights the potential for undiscovered species that could influence current understanding.

  • #31
Ygggdrasil said:
In a recent review discussing the evolution of eukaryotes, I found this figure that I'd like to share with you all.
Hi @Ygggdrasil:

I have been trying to absorb the new organization shown in the figure in post #1, but I am having difficulty understanding the evolutionary lineage categories corresponding to the colors: white, orange, yellow, blue, green, and red. I get that purple represents the eukaryotes, but for the other six colors I can not find any correspnding named lineages. Can you help me?

Regards,
Buzz
 
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  • #32
Buzz Bloom said:
Hi @Ygggdrasil:

I have been trying to absorb the new organization shown in the figure in post #1, but I am having difficulty understanding the evolutionary lineage categories corresponding to the colors: white, orange, yellow, blue, green, and red. I get that purple represents the eukaryotes, but for the other six colors I can not find any correspnding named lineages. Can you help me?

Regards,
Buzz

That's a good question. From what I can tell, the author does not really elaborate on this in the article. I don't know enough about bacterial and archaeal evolution to answer, so if you're really interested, perhaps its worth contacting the author of the article for more information.
 
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  • #33
Hi @Ygggdrasil:

I received permission form Prof. James Lake to post some references about this topic. He also requested that the figures from the original link
should be cited as being from:
Lake, JA, 2015 Eukaryotic Origins, Phil. Trans. R. Soc. B, 370, 20140321. http://dx.doi.org/10.1098/rstb.2014.0321, Vol 370, Issue 1678, 26 September 2015.​
Also, the original link should be cited as
James Lake
Distinguished Prof. MCDBiology and Human Genetics
UCLA
For our latest review on the eocyte (or two domains tree) see the recent review: Eukaryotic Origins, James A. Lake, Accepted 5 May 2015
Philosophical Transactions R. Soc. B, 370, 20140321,
http//dx.doi.org/10.1098/rstb.2014.0321.​

Here are some other references on this topic.

Latest reviews and results supporting the Eocyte tree:
For lab details, including a video of the 2011 Darwin Wallace Medal see:

See additional reviews and results supporting the Eocyte Hypothesis:
http://phenomena.nationalgeographic.com/2012/12/20/redrawing-the-tree-of-life/
http://rspb.royalsocietypublishing.org/content/early/2012/10/18/rspb.2012.17 95.full
http://schaechter.asmblog.org/schaechter/2012/09/begetting-the-eukarya-an-un expected-light.html
http://courses.missouristate.edu/chrisbarnhart/bio121/readings/Zimmer%20Orig in%20of%20Eukaryotes.pdf
http://blogs.sciencemag.org/cgi-bin/mt/mt-search.cgi?tag=eocyte&IncludeBlogs =7
http://rstb.royalsocietypublishing.org/content/364/1527/2197.full.pdf
http://www.pnas.org/content/105/51/20049.full
http://www.yale.edu/ochman/Papers/Ochman_EnvMicro2009aop.pdf​

Regarding the colors in the original figure, he wrote the following:
The major pathways mentioned are photosynthesis – in green – which flows all the way to to the Plants at the top.
Phototrophy, a type of pre-photosynthesis, is shown in yellow and then it evolves into photosynthesis (again the green flow).
And last, the magenta flow goes into the eocytes (the dawn cells) and into the nucleus that is present in all eukaryotes.
These are labeled in the figure at the following url:

Regards,
Buzz
 
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