New genes out of nothing


Share post:

One key question in evolutionary biology is how novel genes arise and develop. Swedish researchers now show how new genes and functions that are advantageous to bacteria can be selected from random DNA sequences. The results are presented in the scientific journal mBio.

New genes out of nothing
Credit: bigstock

How do new genes and functional proteins arise and develop? This is one of the most fundamental issues in evolutionary biology. Two different types of mechanism have been proposed: (1) new genes with novel functions arise from existing genes, and (2) new genes and proteins evolve from random DNA sequences with no similarity to existing genes and proteins. In the present study, the researchers explored the latter type of mechanism: evolution of new genes and proteins from randomised DNA sequences – de novo evolution, as it is called. It is fairly easy to understand that when a gene already exists, it can be modified and acquire a new function. But how does “nothing” turn into a function affording a small advantage that is favoured by natural selection?

The raw material for the experiment was an big library of some 500 million randomised gene sequences, from which peptide sequences with a biological function were identified. In the experiment, random gene sequences were placed on a plasmid and overexpressed. The scientists then investigated whether they could give bacteria a specific, defined property. Were they, for example, able to give the bacteria antibiotic resistance? They identified several short peptides (22-25 amino acids long) that could give the bacteria a high degree of resistance to aminoglycosides, an important class of antibiotics used for severe infections.

“When the project started, we had low expectations. We were amazed when we found peptides able to confer a resistance level 48 times higher,” says Dr Michael Knopp, the study’s lead author.

Through a combination of genetic and functional experiments, the scientists were able to demonstrate that the peptides cause resistance by attaching themselves to bacterial cell membranes and affecting the proton potential across the membrane. The disruption of the proton potential causes a decrease in antibiotic uptake, rendering the bacteria resistant.

“This study is important because it shows that completely random sequences of amino acids can give rise to new, advantageous functions, and that this process of de novo evolution can be studied experimentally in the laboratory,” says Dan I. Andersson, Professor of Medical Bacteriology, who is chiefly responsible for the study.

Source: Uppsala University [June 04, 2019]



Related articles

Domesticated wheat has complex parentage

Certain types of domesticated wheat have complicated origins, with genetic contributions from wild and cultivated wheat populations on...

Aquatic microorganisms offer important window on the history of life

The air, earth and water of our planet are pulsating with living things. Yet, a vast and diverse...

Birds and dinosaurs — joined at the hip

All baby birds have a moment prior to hatching when their hip bone is a tiny replica of...

Metabolic fossils from the origin of life

Life converts food into cells via dense networks involving thousands of reactions. New research uncovers insights as to...

Evolution on the fast lane – one flounder species became two

A research group at the University of Helsinki discovered the fastest event of speciation in any marine vertebrate...

Modern microbial ecosystems provide window to early life on Earth

New research from a University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science-led science team provides...

How a single cell slime mould makes smart decisions without a central nervous system

Having a memory of past events enables us to take smarter decisions about the future. Researchers at the...

Scientists identify essential factors for limb formation

Scientists at the Centro Nacional de Investigaciones Cardiovasculares (CNIC), working in partnership with researchers at the Institut de...