Regulatory RNAs play important roles in the control of gene expression. A major scientific milestone
in the study of regulatory small (s)RNAs was the discovery of RNA interference (RNAi), which
resulted in the Nobel Prize for Fire and Mello (2006). This process is triggered by double stranded
RNA and results in sequence-specific post-transcriptional gene silencing. In insects, the most
speciose class of animals, RNAi constitutes the main antiviral immune response by degrading viral
transcripts. In addition, this mechanism is widely used for reverse genetic studies and it offers novel
opportunities for applications in pest control. While many regulatory sRNA pathway components
are identified in insects, the molecular and cellular mechanisms of systemic spreading of the RNAsignal
and silencing, as well as their role in systemic antiviral immunity, are not fully understood.
Recent preliminary data indicate that cell-free insect hemolymph and media of cultured cells
contain high levels of extracellular sRNAs. Furthermore, we have observed that insect extracellular
vesicles can deliver an RNAi-signal to recipient cells, spreading the silencing effect. Since sRNAs are
well known for their regulatory functions, this points towards the existence of intercellular RNAbased
signalling processes. The current project aims at identifying extracellular sRNAs from insect
cell-free fluids and at investigating their role in systemic RNAi and antiviral immunity in this group of
animals.