The RNA World: Identifying miRNA-Target RNA Pairs as Possible Missing Links in Multi-Network Models

Plant cells contain highly complex and abundant populations of small RNAs that regulate gene expression at many levels, in diverse tissues, and show evidence of regulation under different growth conditions. These molecules have been recognized as important components of signalling networks, but investigations of their contributions to plant signalling pathways have only taken place within the past few years. As sequencing methods have improved, many new microRNAs (miRNAs) have been identified in the most well-studied species; the discovery of miRNAs in less-studied species is just beginning but has been greatly enabled by these new methods. Studies to compile and experimentally validate lists of miRNAs combined with high-throughput expression profiling of small RNAs will better define the extent of small RNA regulation in plant cellular processes. Validation of miRNAs often includes the prediction and verification of their mRNA targets and the identification of these targets can provide insight into the biological role of individual miRNAs and miRNA families. However, the power of this information could be farther reaching if it can be interpreted with other interaction data. The incorporation of pairs of miRNAs and their targets into multi-network models would accomplish this and would likely to provide the missing links in many regulatory pathways. Since approaches to address the function of individual miRNAs in mutants and transgenic plants are labour-intensive, the hypotheses resulting from the models could focus attention on the miRNAs that play pivotal roles in a number of key regulatory pathways.