A Novel Taxon of RNA Viruses Endemic to Planarian Flatworms
Bibliographic record
Abstract
Abstract The phylum Platyhelminthes is composed of both parasitic and non-parasitic flatworms. While the parasitic species have drawn attention for their wide effects on human and livestock heath, free-living flatworms, such as freshwater planarians, have become molecular models of regeneration and stem cell biology in the laboratory. However, one aspect of planarian biology that remains understudied is the relationship between host and any endemic viruses. Here we used searches of multiple transcriptomes from Schmidtea mediterranea asexual strain CIW4 and detected a novel, double-stranded RNA (dsRNA) virus, named S. mediterranea tricladivirus ( SmedTV ), which represents a distinct taxon (proposed new genus) within a larger taxon of monosegmented dsRNA viruses of diverse hosts. Experimental evidence for SmedTV in S. mediterranea CIW4 was obtained through whole-mount in situ hybridization (WISH). SmedTV “expression” (detected by both sense and anti-sense probes) was discrete yet variable from worm to worm and cell type to cell type, suggesting a persistent infection. Single-cell RNA sequencing (scRNAseq) further supported that SmedTV expression was low in stem cells, but substantially higher in multiple, though not all, differentiated tissues, with notable neural enrichment. Interestingly, knockdown of SmedTV by RNA-interference resulted in a “cure” of SmedTV after 10 RNAi doses, and expression remained undetectable by WISH even after 90 days. Due to being able to evade host defenses and the endogenous RNAi pathway, we believe SmedTV represents a novel animal model to study host-virus evolution. Statement of significance Planarians are freshwater flatworms and emerging models to study the molecular mechanisms of adult stem cell and regenerative biology. However, they also live in aquatic environments with high amounts of viruses, bacteria, fungi, and protist pathogens. How the planarian immune system copes with all of these is largely unknown and only 2 types of virus have been described. Here we find a novel dsRNA virus, endemic to multiple types of flatworms. We show that it is a persistent infection, and likely transmits from stem cell to differentiated cell in the planarian, while avoiding endogenous RNA-interference machinery and mechanisms used to suppress viruses. We present this as a new model to study host-virus defense and evolution.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".