Tweaking microRNA-mediated gene regulation for crop improvement

Abstract Many beneficial agronomic traits of crops have been lost in the course of domestication and selective introgression processes. One of the best strategies to prevent the exclusion of beneficial traits during the introgression of novel traits is to selectively fine-tune the expression of some candidate genes or microRNAs (miRNAs). Noncoding regulatory miRNAs of 20–24 nucleotide (nt) length have evolved as specific posttranscriptional regulators that negatively regulate the transcript abundance of their target genes via either cleavage of mRNAs or translational inhibition. In this chapter, we summarize the current knowledge on the role of miRNAs and elaborate their use in miRNA-mediated gene regulation for the improvement of agronomic traits in crop plants. Recent CRISPR-Cas9-based genome engineering technology can be applied to selectively tweak the specific miRNA-target regulation, and thus, the function of the candidate genes to improve crop plants by conferring better productivity or resistance to abiotic or biotic stresses.