Exogenous miRNAs induce post-transcriptional gene silencing in plants

Basics of RNA interference (RNAi) and miRNAs

RNA interference is a form of gene regulation that causes the down-regulation of protein production of a particular gene. RNAi is a natural mechanism and occurs in fungi, plants and animals. There are various short RNAs capable of recognizing a specific target and triggering the RNAi mechanism. These include so-called microRNAs (miRNAs), which are encoded in the genome and play a key role primarily in the gene regulation of the cell or organism. The miRNAs are produced by the cell and induce a reduction in the production of certain proteins.

Results of the Betti et al. study

miRNAs in plants act within the cell in which they are produced and can also be exchanged between individual plant cells. Ultimately, miRNAs are transported throughout the entire plant and act within different cells. The mechanism by which they are transported throughout the plants is not fully known. The study presented here investigated whether miRNAs are exchanged between neighbouring plants and whether they are active in the recipient plant.

Using the model plant Arabidopsis thaliana, the scientists cultivated two plants in a common nutrient solution. One of the two plants produced a specific miRNA, the other plant was a wild type plant. The plant that produced more miRNAs released these into the nutrient medium. The miRNAs were subsequently taken up by the neighbouring wild-type plant, and thus triggered reduced gene regulation of the respective target genes. This changed the phenotype of the wild-type plants, i.e. delayed flowering time, which is known to be triggered by the specific miRNA used.

The scientists showed that plants communicate with each other by exchanging miRNAs and probably warn each other of certain stress conditions. However, the results were the outcome of experimental conditions in hydroponics. Whether this type of communication also occurs in natural conditions was not investigated in the study. Furthermore, it remains unclear how the miRNAs are exchanged and how they are taken up by the recipient plants.