Artificial micrornas and their applications in plant molecular biology

Artificial microRNAs (amiRNAs) are modified endogenous microRNA precursors in which the miRNA:miRNA* duplex is replaced with sequences designed to silence any desired gene. amiRNAs are used as part of new genetic transformation techniques in eukaryotes and have proven to be effective and to excel over other RNA-mediated gene silencing methods in both specificity and stability. amiRNAs can be designed to silence single or multiple genes, it is also possible to construct dimeric amiRNA precursors to silence two non-related genes simultaneously. amiRNA expression is quantitative and allows using constitutive, inducible, or tissue-specific promoters. One main application of amiRNAs is gene functional validation and to this end they have been mostly used in model plants; however, their use can be extended to any species or variety. amiRNA-mediated antiviral defense is another important application with great potential for plant molecular biology and crop improvement, but it still needs to be optimized to prevent the escape of viruses from the silencing mechanism. Furthermore, amiRNAs have propelled research in related areas allowing the development of similar tools like artificial trans-acting small interference RNAs (tasiARNs) and artificial target mimicry. In this review, some applications and advantages of amiRNAs in plant molecular biology are analyzed