The entangled history of animal and plant microRNAs

MicroRNAs (miRNAs) are small RNAs (sRNAs) that regulate gene expression in development and adaptive responses to the environment. The early days in the sRNA field was one of the most exciting and promising moments in modern biology, attracting large investments to the understanding of the underlining mechanisms and their applications, such as in gene therapy. miRNAs and other sRNAs have since been extensively studied in animals and plants, and are currently well established as an important part of most gene regulatory processes in animals and as master regulators in plants. Here, this review presents the critical discoveries and early misconceptions that shaped our current understanding of RNA silencing by miRNAs in most eukaryotes, with a focus on plant miRNAs. The presentation and language used are simple to facilitate a clear comprehension by researchers and students from various backgrounds. Hence, this is a valuable teaching tool and should also draw attention to the discovery processes themselves, such that scientists from various fields can gain insights from the successful and rapidly evolving miRNA field.