MicroRNAs (miRNAs) compose a class of short, noncoding RNAs, 20-24-nucleotides in length, that have been found in eukaryotic organisms ranging from roundworms, to fruit flies, to humans. The founding members of this class of RNAs are lin-4 and let-7, two small RNAs that are processed from a longer stem-loop structure by the Dicer enzyme, and function to control developmental timing in the roundworm C. elegans. Over 150 other miRNAs have since been found in animals.
Dr. David Bartel and colleagues have discovered that miRNAs are also present in plants, where they, like their animal counterparts, may also regulate gene expression during development.
Dr. Bartel and colleagues have identified 16 novel miRNAs in the model plant, Arabidopsis, which share sequence and structural similarities to animal miRNAs. The researchers demonstrate that plant miRNAs are processed by a plant homologue of the Dicer enzyme, CARPEL FACTORY (CAF), suggesting that animal and plant miRNAs share a common processing mechanism, and that the previously described role of CAF in plant development may, in fact, be mediated by miRNAs.
As Dr. Bartel describes, "The discovery that microRNAs are present in plants as well as animals shows that this class of noncoding RNAs arose early in eukaryotic evolution and suggests that microRNAs have been shaping gene expression since the emergence of multicellular life."