Recreate life to understand how life began
09 August 2010 by Jack Szostak
Magazine issue 2772.
Building artificial cells will tell us much about the origins of life – and may explain how Darwinian evolution began, says Nobel laureate Jack Szostak
IMAGINE Earth 4 billion years ago. It is a world of oceans, peppered with volcanic land masses resembling Hawaii and Iceland. The volcanoes spew poisonous gases and the atmosphere is rent by the violent impacts of asteroids and comets. Temperatures range from the incandescent heat of flowing lava to the frozen ice fields of the high polar regions. Shallow ponds on the volcanic islands dry out, then fill with rain, incubating the fragile chemistry that ultimately leads to the emergence of life.
Incubating life's chemical precursors (Image: Scott Kohn/Rex Features)
How extraordinary that cellular life should have arisen in such a harsh environment. The exact nature of that first cell, the basic unit of all life today, is still unknown. It is an exciting puzzle that goes to the heart of the origins of life as we know it. But it is hard to solve: after all, reconstructing such ancient events seems an impossible task. Fortunately, there is much to be learned from a slightly more modest goal: building basic artificial cells in the lab.
I should emphasise that there is a world of difference between this kind of artificial life and the recent feats of Craig Venter and his team at the J. Craig Venter Institute in Rockville, Maryland, and San Diego, California. That team, which includes Nobel laureate Hamilton Smith, achieved a technical milestone by replacing the genome of an existing bacterium with a synthetic genome stitched together from stretches of chemically synthesised DNA. Creating synthetic genomes may ultimately let us redesign existing life forms in ways we can scarcely imagine.
Now let's return to the origin of life. In the late 1990s there were opposing views about the key steps in the process. Many of us argued for the emergence of RNA replication as the most important step because the inheritance of genetic information is central to evolution. Others, however, thought about life from the perspective of structures that would define a boundary between the living system and its environment. They championed the idea that the most important aspect was the emergence of the cell membrane, in the form of self-assembling and self-replicating vesicles.
For over a year in the genetics department of the Harvard Medical School, my then student David Bartel and I argued about the origin of life with Pier Luigi Luisi, then at the Swiss Federal Institute of Technology in Zurich. Bartel and I were firmly in the "genetics first" camp, since our research was focused on nucleic acids. Luisi, a pioneer of vesicle research, thought only about membranes and compartmentalisation.
As we sparred, a remarkable thing happened: our views started to converge. Finally, we agreed that for life to emerge, both membranes and genetic material needed to come together, compatibly, to endow the first cells with the capacity to evolve. We presented this synthesis in a paper in Nature in 2001. It was a real turning point in my origins research. Up to that point, my work on RNA had been inspired by Tom Cech at the University of Colorado, Boulder, who shared the Nobel prize in chemistry in 1989 for showing how RNA could carry out catalysis as well as transmit information. For years, my team and I wrestled with the problem of how RNA could catalyse its own replication. But after our debates with Luisi, I came to appreciate that cell membrane growth and division was just as important and that both problems would have to be solved.
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Read more here/Leia mais aqui: New Scientist
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