Darwin iria gostar: a origem do mundo RNA - o destino das nucleobases em pequenas lagoas quentes

quarta-feira, outubro 04, 2017

Origin of the RNA world: The fate of nucleobases in warm little ponds

Ben K. D. Pearce a,b,1, Ralph E. Pudritz a,b,c,d, Dmitry A. Semenov c, and Thomas K. Henning c  

Author Affiliations

a Origins Institute, McMaster University, Hamilton, ON L8S 4M1, Canada;

b Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada;

c Planet and Star Formation Department, Max Planck Institute for Astronomy, 69117 Heidelberg, Germany;

d Institute for Theoretical Astrophysics, Center for Astronomy Heidelberg, 69120 Heidelberg, Germany

Edited by Donald E. Canfield, Institute of Biology and Nordic Center for Earth Evolution, University of Southern Denmark, Odense M., Denmark, and approved August 28, 2017 (received for review June 7, 2017)

Source/Fonte: Springer Link



There are currently two competing hypotheses for the site at which an RNA world emerged: hydrothermal vents in the deep ocean and warm little ponds. Because the former lacks wet and dry cycles, which are well known to promote polymerization (in this case, of nucleotides into RNA), we construct a comprehensive model for the origin of RNA in the latter sites. Our model advances the story and timeline of the RNA world by constraining the source of biomolecules, the environmental conditions, the timescales of reaction, and the emergence of first RNA polymers.


Before the origin of simple cellular life, the building blocks of RNA (nucleotides) had to form and polymerize in favorable environments on early Earth. At this time, meteorites and interplanetary dust particles delivered organics such as nucleobases (the characteristic molecules of nucleotides) to warm little ponds whose wet–dry cycles promoted rapid polymerization. We build a comprehensive numerical model for the evolution of nucleobases in warm little ponds leading to the emergence of the first nucleotides and RNA. We couple Earth’s early evolution with complex prebiotic chemistry in these environments. We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years). Their constituent nucleobases were primarily meteoritic in origin and not from interplanetary dust particles. Ponds appeared as continents rose out of the early global ocean, but this increasing availability of “targets” for meteorites was offset by declining meteorite bombardment rates. Moreover, the rapid losses of nucleobases to pond seepage during wet periods, and to UV photodissociation during dry periods, mean that the synthesis of nucleotides and their polymerization into RNA occurred in just one to a few wet–dry cycles. Under these conditions, RNA polymers likely appeared before 4.17 billion years ago.

life origins astrobiology planetary science meteoritics RNA world


1To whom correspondence should be addressed. Email: pearcbe@mcmaster.ca.

Author contributions: B.K.D.P., R.E.P., D.A.S., and T.K.H. designed research; B.K.D.P. performed research; B.K.D.P. and R.E.P. analyzed data; and B.K.D.P., R.E.P., D.A.S., and T.K.H. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1710339114/-/DCSupplemental.


Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao Portal Periódicos CAPES/MEC podem ler gratuitamente este artigo do PNAS e mais 33.000 publicações científicas.