Special Issue "The RNA World: Known Knowns and Known Unknowns"

Dear Colleagues,

Understanding how life arose is a fundamental problem of biology. One of the prevailing hypotheses is the ‘RNA world’. The general notion of an ‘RNA world’ is that there was an early stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules acted both as genetic polymers and as catalysts. Later on, proteins became the catalyst of life and RNA reduced its function predominantly to information storage. In a more practical manner, the ‘RNA world’ can be regarded as a set of models that seek to explain a hypothetical period in the early evolution of life on Earth. Although the basic premise is generally well agreed-upon, specifics vary widely, depending on the assumptions and implications of each model. In this context, the ‘RNA world’ takes different forms for different researchers.

Even though there is evidence that an ‘RNA world’ existed before life was based on DNA and proteins, there are compelling arguments against the idea that life on Earth began with this molecule. While it seems safe to assume that all pieces necessary to create RNA molecules were available in a prebiotic environment, how these components could have assembled into replicating, evolving polynucleotides is an ongoing matter of debate. It is precisely here where the granularity of the ‘RNA world’ arises, as there are several alternatives to how the chemical stability of said polymer could be achieved; for instance, by interaction with amino acids, small peptides, metal ions, minerals, as well as with a wide range of organic molecules. Some of the main challenges of the ‘RNA world’ are related to the high complexity and low stability of RNA molecules, and the possible limitations of the catalytic repertoire of RNA. Although some recent experimental findings provide reason for optimism, the problem of the origin of the RNA world is far from being solved.

Fortunately, the repertoire of RNA activity is also extensive in all extant life, including in gene expression, essential biocatalysis, and host defense mechanisms. The constant interrogation of the modern non-hypothetical RNA world, together with research on prebiotically plausible scenarios, helps us gain some important insights into what a primordial ‘RNA world’ could have looked like. The objective of this Special Issue is to cover the state-of-the-art of developments related to the ‘RNA world’ hypothesis under the premise that there is no unique definition of the RNA world. We welcome research papers, review articles, and case reports of experimental, theoretical, or computational nature.

Dr. Celia Blanco
Dr. Alberto Vázquez-Salazar
Dr. Ranajay Saha
Guest Editors

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• RNA world
• origins of life
• evolutionary biology
• molecular evolution
• ribozymes
• self-replication
• catalysis
• polynucleotides