News: Earth's Original Ancestor Was 'LUCA'

Earth's Original Ancestor Was 'LUCA'

ScienceDaily (Dec. 19, 2008) - An evolutionary geneticist from the
Université de Montréal, together with researchers from the French cities of
Lyon and Montpellier, have published a ground-breaking study that
characterizes the common ancestor of all life on earth, LUCA (Last Universal
Common Ancestor).

Their findings, presented in a recent issue of Nature, show that the
3.8-billion-year-old organism was not the creature usually imagined.

The study changes ideas of early life on Earth. "It is generally believed
that LUCA was a heat-loving or hyperthermophilic organism. A bit like one of
those weird organisms living in the hot vents along the continental ridges
deep in the oceans today (above 90 degrees Celsius)," says Nicolas
Lartillot, the study's co-author and a bio-informatics professor at the
Université de Montréal. "However, our data suggests that LUCA was actually
sensitive to warmer temperatures and lived in a climate below 50 degrees."

The research team compared genetic information from modern organisms to
characterize the ancient ancestor of all life on earth. "Our research is
much like studying the etymology of modern languages so as to reveal
fundamental things about their evolution," says professor Lartillot. "We
identified common genetic traits between animals, plant, bacteria, and used
them to create a tree of life with branches representing separate species.
These all stemmed from the same trunk - LUCA, the genetic makeup that we
then further characterized."

Reconciling conflicting data

The group's findings are an important step towards reconciling conflicting
ideas about LUCA. In particular, they are much more compatible with the
theory of an early RNA world, where early life on Earth was composed of
ribonucleic acid (RNA), rather than deoxyribonucleic acid (DNA).

However, RNA is particularly sensitive to heat and is unlikely to be stable
in the hot temperatures of the early Earth. The data of Dr. Lartillot with
his collaborators indicate that LUCA found a cooler micro-climate to
develop, which helps resolve this paradox and shows that environmental micro
domains played a critical role in the development of life on Earth.

From RNA to DNA: Proof of evolution

"It is only in a subsequent step that LUCA's descendants discovered the more
thermostable DNA molecule, which they independently acquired (presumably
from viruses), and used to replace the old and fragile RNA vehicle. This
invention allowed them to move away from the small cool microclimate,
evolved and diversify into a variety of sophisticated organisms that could
tolerate heat," adds Dr. Lartillot.

The study was authored by Bastien Boussau (CNRS, Université Lyon), Samuel
Blanquart (LIRMM, CNRS: France), Anamaria Necsulea (CNRS, Université Lyon),
Nicolas Lartillot (Université Montreal), and Manolo Gouy (CNRS, Université
Lyon).


Funding was provided through grants from Action Concerteé Incitative
IMPBIO-MODELPHYLO and ANR PlasmoExplore.

Journal reference:

1.. Bastien Boussau, Samuel Blanquart, Anamaria Necsulea, Nicolas
Lartillot, Manolo Gouy. Parallel adaptations to high temperatures in the
Archaean eon. Nature, 2008; 456 (7224): 942 DOI: 10.1038/nature07393

University of Montreal (2008, December 19). Earth's Original Ancestor Was
'LUCA'. ScienceDaily. Retrieved December 20, 2008, from
http://www.sciencedaily.com/releases/2008/12/081217124200.htm

Posted by
Robert Karl Stonjek


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