Genetic manipulation of microRNAs: approaches and limitations

Abstract

MicroRNAs (miRNAs) are endogenous, small regulatory RNAs (20–24 nt) that bind to complementary sites in the target mRNA molecules and lead to their degradation or translational inhibition. miRNAs regulate the spatial–temporal accumulation of target mRNAs, thereby governing several downstream biological processes and pathways. Various studies over the years have revealed that miRNAs play essential roles in controlling key developmental processes such as embryogenesis, development of root and shoot, leaf polarity, and phase transition along with the plant responses toward numerous biotic and/or abiotic stresses. The functional characterization of miRNAs and fine-tuning of the approaches using miRNAs to boost productivity and tolerance towards abiotic or biotic stresses in commercially important crops are very important. Mostly, approaches used for the functional characterization of miRNAs are based on modulating transcription of miRNA genes by employing genetic engineering tools. These approaches include the use of artificial miRNA genes, target mimic, editing of miRNAs using ZNF proteins, meganucleases, TALENs and most newly emerged CRISPR/Cas9. This review offers a brief overview of the biogenesis and functions of miRNAs in governing key biological processes. It also provides an insight into different approaches and bottlenecks to improve biologically and agronomically important traits through the modulation of miRNA function.