Navigating trade-offs: the adaptive significance of A-to-I RNA editing in fungi, bacteria, and animals

A-to-I RNA editing is a widespread epitranscriptomic mechanism that diversifies RNA transcripts by converting adenosine to inosine. This process, catalyzed by specific deaminases, mimics A-to-G mutations at the RNA level, often resulting in protein recoding. It occurs in animals, fungi, and bacteria, with regulation that is often specific to tissue, developmental stage, or environmental conditions. For example, in animal nervous systems, fungal sexual development, and bacterial stress responses, A-to-I editing plays a crucial role. This editing mechanism enhances protein diversity and flexibility, helping organisms mitigate evolutionary trade-offs across varying tissues and conditions. Evolutionary studies suggest that conserved recoding events in animals are likely adaptive, whereas in fungi, recoding events tend to be generally adaptive. Research has shown that A-to-I editing is vital for sexual reproduction in fungi, providing a selective advantage by alleviating survival-reproduction trade-offs. In bacteria, A-to-I editing fine-tunes the balance between growth and stress resistance. While the adaptive role of A-to-I editing in animals remains debated, it is recognized for its significance in physiological processes such as reproduction and lifespan in Drosophila, as well as nervous system function in cephalopods. Overall, A-to-I RNA editing expands the functional repertoire of the genome, facilitating adaptation to diverse environments.