MicroRNAs in crop improvement: fine-tuners for complex traits

One of the most common challenges for both conventional and modern crop improvement is that the appearance of one desirable trait in a new crop variety is always balanced by the impairment of one or more other beneficial characteristics. The best way to overcome this problem is the flexible utilization of regulatory genes, especially genes that provide more efficient and precise regulation in a targeted manner. MicroRNAs (miRNAs), a type of short non-coding RNA, are promising candidates in this area due to their role as master modulators of gene expression at the post-transcriptional level, targeting messenger RNAs for cleavage or directing translational inhibition in eukaryotes. We herein highlight the current understanding of the biological role of miRNAs in orchestrating distinct agriculturally important traits by summarizing recent functional analyses of 65 miRNAs in 9 major crops worldwide. The integration of current miRNA knowledge with conventional and modern crop improvement strategies is also discussed.