miRNA communication between plants

In the recent years research on RNA interference (RNAi) applied to agriculture led to the development of a new approaches for the modulation of gene expression in plants, also through the exogenous application of double-stranded RNA (ds-RNA). ds-RNA can specifically repress a target gene whose RNA sequence is complementary to that of the ds-RNA, thus leading to modified expression of the target gene(s) and thus modifying the physiology of the plant. Several AG-tech companies are developing technologies based on RNAi, either by using a plant transformation approach or by developing synthetic dsRNAs to be sprayed on plants in order to obtain the desired gene repression and thus affecting the desired trait. It is currently unknown if RNAs can represent signaling molecules able to trigger their effects also when fed exogenously. Our results showed that miRNAs are secreted by plant roots to the surrounding medium and that they are quite stable even in a non-sterile environment. Interestingly, we observed effects in wild-type plants that were grown together with Arabidopsis plants over-expressing specific miRNAs, suggesting that miRNAs secreted to the external medium could be uptaken by other plants. Experiments performed feeding an RNA extracts to Arabidopsis seedlings confirmed that an effect can be observed in terms of repression of miRNA’s target genes. These data strongly suggest that miRNAs are not only mobile RNAs inside the plant but can also represent mobile signals among separate individual plants.