Rise in Oxygen Drove Evolution of Animal Life 550 Million Years Ago
ScienceDaily (Dec. 18, 2010) — Researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) at the University of Oxford have uncovered a clue that may help to explain why the earliest evidence of complex multicellular animal life appears around 550 million years ago, when atmospheric oxygen levels on the planet rose sharply from 3% to their modern day level of 21%.
Original image of Trichoplax adhaerens. (Credit: Copyright Karolin von der Chevallerie, University of Hannover)
The team, led by Professor Chris Schofield, has found that humans share a method of sensing oxygen with the world's simplest known living animal -- Trichoplax adhaerens -- suggesting the method has been around since the first animals emerged around 550 million years ago.
This discovery, published in the January 2011 edition of EMBO Reports, throws light on how humans sense oxygen and how oxygen levels drove the very earliest stages of animal evolution.
Professor Schofield said "It's absolutely necessary for any multicellular organism to have a sufficient supply of oxygen to almost every cell and so the atmospheric rise in oxygen made it possible for multicellular organisms to exist.
"But there was still a very different physiological challenge for these organisms than for the more evolutionarily ancient single-celled organisms such as bacteria. Being multicelluar means oxygen has to get to cells not on the surface of the organism. We think this is what drove the ancesters of Trichoplax adhaerens to develop a system to sense a lack of oxygen in any cell and then do something about it."
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Bibliography/Bibliografia:
1. Christoph Loenarz, Mathew L Coleman, Anna Boleininger, Bernd Schierwater, Peter W H Holland, Peter J Ratcliffe, Christopher J Schofield.
The hypoxia-inducible transcription factor pathway regulates oxygen sensing in the simplest animal, Trichoplax adhaerens. EMBO reports, 2010; DOI: 10.1038/embor.2010.170
The hypoxia-inducible transcription factor pathway regulates oxygen sensing in the simplest animal, Trichoplax adhaerens
Christoph Loenarz, Mathew L Coleman, Anna Boleininger, Bernd Schierwater, Peter W H Holland, Peter J Ratcliffe and Christopher J Schofield
Abstract
The hypoxic response in humans is mediated by the hypoxia-inducible transcription factor (HIF), for which prolyl hydroxylases (PHDs) act as oxygen-sensing components. The evolutionary origins of the HIF system have been previously unclear. We demonstrate a functional HIF system in the simplest animal, Trichoplax adhaerens: HIF targets in T. adhaerens include glycolytic and metabolic enzymes, suggesting a role for HIF in the adaptation of basal multicellular animals to fluctuating oxygen levels. Characterization of the T. adhaerens PHDs and cross-species complementation assays reveal a conserved oxygen-sensing mechanism. Cross-genomic analyses rationalize the relative importance of HIF system components, and imply that the HIF system is likely to be present in all animals, but is unique to this kingdom.
2. Kalle T Rytkönen, Jay F Storz.
Evolutionary origins of oxygen sensing in animals. EMBO reports, 2010; DOI:10.1038/embor.2010.192
Evolutionary origins of oxygen sensing in animals
Kalle T Rytkönen and Jay F Storz
Abstract
EMBO Rep (2010) advance online publication. doi: 10.1038/embor.2010.170
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NOTA DESTE BLOGGER:
Teorias científicas de longo alcance histórico, especialmente as que se propõem explicar a origem e evolução do universo e da vida, sofrem de tremendas dificuldades no contexto de justificação teórica. Neste caso aqui, como explicar este evento único há 550 milhões de anos atrás? Como corroborar isso no contexto de justificação teórica? É preciso aceitar a priori que realmente assim se sucedeu? O presente é a chave que explica o passado? Somente neste caso aqui é que se aplica isso?
Se tiver bastante oxigênio, então, voilá, évolution, chérie, pois a evolução é muito mais inteligente do que você, idiota! (Agradeço, mas não lembro o nome ao cientista evolucionista que nos brindou com esta pérola retórica).
Fui, nem sei por que, pensando, está faltando oxigênio epistemológico em grandes quantidades, especialmente o oxigênio baconiano...
