Evolution of complexity in miRNA-mediated gene regulation systems

Using Arabidopsis microRNA (miRNA)-mediated gene regulation system as a model, we investigated how complex systems evolve with special attention to selection to maintain the systems. We found that the copy number of miRNA genes within each system is a key factor to determine the complexity of the system, indicating a crucial role of gene duplication to increase the complexity. Furthermore, we show that the mode of selection to maintain the systems depend on their complexity levels.