MicroRNAs (MiRNAs) are not only regulators of gene expression patterns, but also play an essential role in the coordination of complex developmental processes through their extensive integration within genetic networks. Flowering is critical for the reproduction of angiosperms. By surveying a large amount of literature, Dr. LUO Yan of Xishuangbanna Tropical Botanical Garden (XTBG) and her colleagues first discussed the conservation of miRNAs and their targets. The researchers then summarized their contribution to three developmental phases of flower development, including the floral transition, the floral patterning, and the development of floral organs.

According to their literature review, at least nine conserved miRNA families have been reported to play key roles during flower development in plants, including miR156, miR159, miR160, miR164, miR166/165, miR167, miR169, miR172, and miR319. The phylogenetic distribution of the nine miRNA families across various species from all major lineages of land plants indicated the high levels of their conservation. Of the nine miRNA families, miR164 was found in both angiosperms and gymnosperms, and thus appeared to be conserved across all spermatophytes. Members of the miR159, miR169, and miR172 families were found in angiosperms, gymnosperms, and ferns, and thus appeared to be conserved across all tracheophytes. However, the five remaining families (miR156, miR160, miR166/165, miR167, and miR319) were found not only in dicots and monocots but also in gymnosperms, lycopods, and mosses, and thus appeared to be conserved across all embryophytes.

Analysis of the level of conservation of miRNA-regulated systems in a variety of plant species revealed that miRNAs and their targets affected a broad spectrum of flower developmental programs, and that their regulatory modules were also broadly conserved across all angiosperms.

MiRNAs and their targets are key components in complex networks that control flower development. The interactions between miRNAs, their targets, regulatory factors that act upstream of miRNAs, and other genes involved in flower development have been extensively characterized in Arabidopsis, rice, and maize. However, the conserved miRNA-target modules that are believed to control flowering require further investigation in other species