Ligation of random oligomers leads to emergence of autocatalytic sequence network

TL;DR

This study demonstrates how enzyme-based templated ligation of random DNA oligomers under temperature cycling leads to the emergence of nontrivial, evolution-like sequence patterns and a multiscale ligation landscape, shedding light on early molecular evolution.

Contribution

It reveals how nontrivial sequence patterns and a multiscale ligation landscape emerge from random DNA oligomers through templated ligation and temperature cycling, without explicit selection.

Findings

Emergence of sequence patterns with A-rich and T-rich pools.

Development of a multiscale ligation landscape.

DNA ligation dynamics resemble Darwinian evolution.

Abstract

The emergence of longer information-carrying and functional nucleotide polymers from random short strands was a major stepping stone at the dawn of life. But the formation of those polymers under temperature oscillation required some form of selection. A plausible mechanism is template-based ligation where theoretical work already suggested a reduction in information entropy. Here, we show how nontrivial sequence patterns emerge in a system of random 12mer DNA sequences subject to enzyme-based templated ligation reaction and temperature cycling. The strands acted both as a template and substrates of the reaction and thereby formed longer oligomers. The selection for templating sequences leads to the development of a multiscale ligation landscape. A position-dependent sequence pattern emerged with a segregation into mutually complementary pools of A-rich and T-rich sequences. Even without selection for function, the base pairing of DNA with ligation showed a dynamics resembling Darwinian evolution.