Related Experiment Video
Updated: Jan 19, 2026

Planarian Immobilization, Partial Irradiation, and Tissue Transplantation
Published on: August 6, 2012
Planarians recruit piRNAs for mRNA turnover in adult stem cells
Iana V Kim1, Elizabeth M Duncan2, Eric J Ross2,3
1Gene regulation by Non-coding RNA, Elite Network of Bavaria and University of Bayreuth, 95447 Bayreuth, Germany.
Abstract:
PIWI proteins utilize small RNAs called piRNAs to silence transposable elements, thereby protecting germline integrity. In planarian flatworms, PIWI proteins are essential for regeneration, which requires adult stem cells termed neoblasts. Here, we characterize planarian piRNAs and examine the roles of PIWI proteins in neoblast biology. We find that the planarian PIWI proteins SMEDWI-2 and SMEDWI-3 cooperate to degrade active transposons via the ping-pong cycle. Unexpectedly, we discover that SMEDWI-3 plays an additional role in planarian mRNA surveillance. While SMEDWI-3 degrades numerous neoblast mRNAs in a homotypic ping-pong cycle, it is also guided to another subset of neoblast mRNAs by antisense piRNAs and binds these without degrading them. Mechanistically, the distinct activities of SMEDWI-3 are primarily dictated by the degree of complementarity between target mRNAs and antisense piRNAs. Thus, PIWI proteins enable planarians to repurpose piRNAs for potentially critical roles in neoblast mRNA turnover.
Related Concept Videos
piRNA - Piwi-interacting RNAs
Whole Body Regeneration
Riboswitches
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
Bacterial RNA Polymerase
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
Eukaryotic RNA Polymerases
All three eukaryotic RNAPs require specific transcription factors, of which the...
RNA Stability

