Functional diversity of microRNA variants in plants

MicroRNAs (miRNAs) are small noncoding RNAs that play a crucial role in plant growth, development, and stress responses by regulating target gene expression. With the development of high-throughput sequencing technology, it has been facilitated to identify new miRNAs, as well as diversity and variability of miRNA variants. miRNA variants share the sequences with other closely related miRNAs and contain length and/or sequence variations at the 5’-, 3’-ends, as well as internal positions. They originate from the same miRNA precursor or from the diversity of members in the same miRNA family. It has been reported that tissue- or condition-specific variation in the relative abundance of different miRNA variants could contribute to differential functions of those in development or stress responses. In addition, the diversity of miRNA variants affects stability, loading efficiency onto AGO, and target selection. In this review, the diversification of miRNA sequences and the evidences of the distinct functional role of miRNA variants will be discussed.