Identification of miRNAs and their targets in wheat (Triticum aestivum L.) by EST analysis.

MicroRNAs (miRNAs) are a newly discovered class of noncoding small RNAs that regulate gene expression by directing target mRNA cleavage or translational inhibition. A large number of miRNAs have been identified in plants. Increasing evidence has shown that miRNAs play multiple roles in plant biological processes. So far, identification of miRNAs has been limited to a few model plant species, whose genomes have been sequenced. Wheat (Triticum aestivum L.) is one of the most important cereal crops worldwide. To date, only a few conserved miRNAs have been predicted in wheat. Here, we showed the conserved miRNAs identified in wheat by expressed sequence tag (EST) analysis. All previously known miRNAs from Arabidopsis, rice, and other plant species were used in a BLAST search against the wheat EST database to identify novel wheat miRNAs by a series of filtering criteria. By this strategy, we identified 62 conserved miRNAs, belonging to 30 miRNA families, 48 of which were newly discovered in wheat. These newly identified wheat miRNAs may regulate 287 potential targets, which are involved in development, signal transduction, metabolic pathways, disease resistance, ion transportation, and environmental stress response.