Regulation of plant miRNA biogenesis


Micro (mi)RNAs are small regulatory RNA molecules involved in post-transcriptional silencing of their target mRNAs.  In plants, these miRNAs target mRNAs coding for transcription factors and key regulators, thus modulating plant development, defence, and metabolic processes.  miRNAs mostly originate from MIR genes that are transcribed to long primary (pri)miRNA transcripts by Pol II.  These pri-miRNA transcripts fold-back to give rise specific stem-loop structures that are cleaved by Dicer-like (DCL) proteins to Pre-miRNA intermediates.  Pre-miRNAs are precisely processed into mature miRNA/miRNA* duplex of 20-22 nt length by DCL1 with the help of few accessory proteins.  It is not known why only one or rarely more than one miRNA results from these long dsRNA precursors.  In this review, we discuss recent studies including our unpublished work on structural and sequence determinants of plant miRNAs that distinguish them from their precursor regions. These determinants play a major role in accurate and precise dicing of miRNAs from their precursors, thus contributing to abundance and stability of mature miRNAs.

Special Section on RNA Biology