Advantage looping: Gene regulatory circuits between microRNAs and their target transcription factors in plants.

The 20-24 nucleotide microRNAs (miRNAs) and their target transcription factors (TF) have emerged as key regulators of diverse processes in plants, including organ development and environmental resilience. In several instances, the mature miRNAs degrade the TF-encoding transcripts, while their protein products in turn bind to the promoters of the respective miRNA-encoding genes and regulate their expression, thus forming feedback loops (FBLs) or feedforward loops (FFLs). Computational analysis suggested that such miRNA-TF loops are recurrent motifs in gene regulatory networks (GRNs) in plants as well as animals. In recent years, modeling and experimental studies have suggested that plant miRNA-TF loops in GRNs play critical roles in driving organ development and abiotic stress responses. Here, we discuss the miRNA-TF FBLs and FFLs that have been identified and studied in plants over the past decade. We then provide some insights into the possible roles of such motifs within GRNs. Lastly, we provide perspectives on future directions for dissecting the functions of miRNA-centric GRNs in plants.