Synthetic biology takes on ancient evolutionary mysteries
16 Nov 2018 by qmwwwtqmqt.d qmwwwtqmqt.d
Synthetic biologists in the US have engineered organisms similar to those thought to have lived billions of years ago allowing them to study ancient evolutionary mysteries.
The team from Scripps Research in California created microorganisms that may recapitulate key features of organisms thought to have lived billions of years ago, allowing them to explore questions about how life evolved from inanimate molecules to single-celled organisms to complex, multicellular life.
“These engineered organisms will allow us to probe two key theories about major milestones in the evolution of living organisms – the transition from the RNA world to the DNA world and the transition from prokaryotes to eukaryotes with mitochondria,” says Dr Peter Schultz, president of Scripps Research. “Access to readily manipulated laboratory models enables us to seek answers to questions about early evolution that were previously intractable.”
By studying one of these engineered organisms – a bacterium whose genome consists of RNA and DNA – the scientists hope to shed light on the early evolution of genetic material, including the theorized transition from a world where most life relied solely on the genetic molecule RNA to one where DNA serves as the primary storehouse of genetic information.
Using a second engineered organism, a genetically modified yeast containing an endosymbiotic bacterium, they hope to better understand the origins of cellular power plants called mitochondria. Mitochondria provide essential energy for the cells of eukaryotes, a broad group of organisms that possesses complex, nucleus-containing cells.
“In science class, students learn that DNA leads to RNA which in turn leads to proteins – that’s a central dogma of biology – but the RNA world hypothesis turns that on its head,” said Dr Angad Mehta, postdoctoral research associate at Scripps Research. “For the RNA world hypothesis to be true, you have to somehow get from RNA to a DNA genome, yet how that might have happened is still a very big question among scientists.”
Mehta cautions that their work so far has focused on characterizing this chimeric RNA-DNA genome and its effect on bacterial growth and replication but hasn’t explicitly explored questions about the transition from the RNA world to the DNA world. But, he says, the fact that E. coli with half its genome comprised of RNA can survive and replicate is remarkable and seems to support the possibility of the existence of evolutionarily transitional organisms possessing hybrid RNA-DNA genomes.
The work is reported in two papers, in the Proceedings of the National Academy of Sciences (PNAS) and Journal of the American Chemical Society (JACS).
