Missing Pieces in the Puzzle of Plant MicroRNAs

Abstract

Plant microRNAs (miRNAs) are important regulatory switches. Recent advances have revealed many regulatory layers between the two essential processes, miRNA biogenesis and function. However, how these multilayered regulatory processes ultimately control miRNA gene regulation and connects miRNAs and plant responses with the surrounding environment is still largely unknown. In this opinion article, we propose that the miRNA pathway is highly dynamic and plastic. The apparent flexibility of the miRNA pathway in plants appears to be controlled by a number recently identified proteins and poorly characterized signaling cascades. We further propose that altered miRNA accumulation can be a direct consequence of the rewiring of interactions between proteins that function in the miRNA pathway, an avenue that remains largely unexplored. Plant miRNAs are produced in nuclear dicing bodies (D-bodies).Plant miRNAs can guide either transcript cleavage or translation inhibition, and these mechanisms of silencing are defined by the dicer partnering proteins, presumably in the D-bodies.Newly discovered proteins involved in D-body formation and activity suggest the presence of a complex network of connections among D-body activity, signaling cascades, and responses to the surrounding environment.