A Timely Review of Cross-Kingdom Regulation of Plant-Derived MicroRNAs

MicroRNAs (miRNAs) belong to a class of non-coding RNAs that suppress gene expression by complementary oligonucleotide binding to the sites in target messenger RNAs. Numerous studies have demonstrated that miRNAs play crucial role in virtually all cellular processes of both plants and animals, such as cell growth, cell division, differentiation, proliferation and apoptosis. The study of rice MIR168a has demonstrated for the first time that exogenous plant MIR168a influences cholesterol transport in mice by inhibiting low-density lipoprotein receptor adapter protein 1 expression. Inspired by this finding, the cross-kingdom regulation of plant-derived miRNAs has drawn a lot of attention because of its capability to provide novel therapeutic agents in the treatment of miRNA deregulation-related diseases. Notably, unlike mRNA, some plant miRNAs are robust because of their 3′ end modification, high G, C content, and the protection by microvesicles, miRNAs protein cofactors or plant ingredients. The stability of these small molecules guarantees the reliability of plant miRNAs in clinical application. Although the function of endogenous miRNAs has been widely investigated, the cross-kingdom regulation of plant-derived miRNAs is still in its infancy. Herein, this review summarizes the current knowledge regarding the anti-virus, anti-tumor, anti-inflammatory, anti-apoptosis, immune modulation, and intestinal function regulation effects of plant-derived miRNAs in mammals. It is expected that exploring the versatile role of plant-derived miRNAs may lay the foundation for further study and application of these newly recognized, non-toxic, and inexpensive plant active ingredients.