MicroRNAs and their regulatory roles in plants

MicroRNAs (miRNAs) are small, endogenous RNAs that regulate gene expression in plants and animals. In plants, these similar to 21-nucleotide RNAs are processed from stem-loop regions of long primary transcripts by a Dicer-like enzyme and are loaded into silencing complexes, where they generally direct cleavage of complementary mRNAs. Although plant miRNAs; have some conserved functions extending beyond development, the importance of miRNA-directed gene regulation during plant development is now particularly clear. Identified in plants less than four years ago, miRNAs; are already known to play numerous crucial roles at each major stage of development-typically at the cores of gene regulatory networks, targeting genes that are themselves regulators, such as those encoding transcription factors and F-box proteins.