Punctuated plastome reduction and host–parasite horizontal gene transfer in the holoparasitic plant genus <i>Aphyllon</i>
Bibliographic record
Abstract
Foundational studies of chloroplast genome (plastome) evolution in parasitic plants have focused on broad trends across large clades, particularly among the Orobanchaceae, a species-rich and ecologically diverse family of root parasites. However, the extent to which such patterns and processes of plastome evolution, such as stepwise gene loss following the complete loss of photosynthesis (shift to holoparasitism), are detectable at shallow evolutionary time scale is largely unknown. We used genome skimming to assemble eight chloroplast genomes representing complete taxonomic sampling of Aphyllon sect. Aphyllon, a small clade within the Orobanchaceae that evolved approximately 6 Ma, long after the origin of holoparasitism. We show substantial plastome reduction occurred in the stem lineage, but subsequent change in plastome size, gene content, and structure has been relatively minimal, albeit detectable. This lends additional fine-grained support to existing models of stepwise plastome reduction in holoparasitic plants. Additionally, we report phylogenetic evidence based on an rbcL gene tree and assembled 60+ kb fragments of the Aphyllon epigalium mitochondrial genome indicating host-to-parasite horizontal gene transfers (hpHGT) of several genes originating from the plastome of an ancient Galium host into the mitochondrial genome of a recent common ancestor of A. epigalium . Ecologically, this evidence of hpHGT suggests that the host–parasite associations between Galium and A. epigalium have been stable at least since its subspecies diverged hundreds of thousands of years ago.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".