Bioinformatic identification and expression analysis of new microRNAs from wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

As an essential regulatory component in plants, microRNAs (miRNAs) have been intensively studied over the past decade. Although hundreds of miRNAs have been identified and analyzed in many important crops and model plants, very little is known about the function of common wheat (Triticum aestivum L.) miRNAs. In this study, we performed computational prediction of novel wheat miRNAs based on BLAST searches of the expressed sequence tag database. The expression profiles of all miRNAs were performed for both vegetative and reproductive tissues to identify developmentally regulated miRNAs. A total of 19 new miRNAs belonging to 12 MIR families were identified using stringent criteria for miRNA annotation. For all of the miRNAs, the secondary structures of their precursor sequences were predicted. Two pairs of distinct miRNAs were found to be located on the same precursor. The predicted miRNAs were experimentally verified by a stem-loop qRT-PCR-based assay. The expression profiles were performed in both vegetative and reproductive tissues to find the potential correlations between the developmental phase and miRNA activity. Thirteen out of 19 miRNAs were upregulated at certain phases of plant development, and three of them (miR319, miR395, and miR171) showed the greatest expression in young spikes during microsporogenesis. Our results provide useful information for future studies of miRNA-mediated regulation of flower and grain development in wheat.