The plastomes of <i>Hyalomonas oviformis</i> and <i>Hyalogonium fusiforme</i> evolved dissimilar architecture after the loss of photosynthesis
Bibliographic record
Abstract
Abstract The loss of photosynthesis in land plants and algae is typically associated with parasitism but can also occur in free-living species, including chlamydomonadalean green algae. The plastid genomes (ptDNAs) of colorless chlamydomonadalean species are surprisingly diverse in architecture, including highly expanded forms ( Polytoma uvella, Leontynka pallida ) as well as outright genome loss ( Polytomella species). Here, we explore the ptDNAs of Hyalomonas (Hm.) oviformis (SAG 62-27; formerly known as Polytoma oviforme ) and Hyalogonium (Hg.) fusiforme (SAG 62-1c), each representing independent losses of photosynthesis within the Chlamydomonadales. The Hm. oviformis ptDNA is moderately sized (132 kb), smaller than that of its photosynthetic relative Hyalomonas chlamydogama SAG 11-48b (198.3 kb), with a reduced gene complement but still encoding the ATPase subunits. The Hg. fusiforme plastome, however, is the largest yet observed in colorless plants or algae (~463 kb) and has a coding repertoire that is almost identical to that of its photosynthetic relatives in the genus Chlorogonium . Furthermore, the ptDNA of Hg. fusiforme shows no clear evidence of pseudogenization, which is consistent with our analyses showing that Hg. fusiforme is the non-photosynthetic lineage of most recent origin among the known colorless Chlamydomonadales. Together, these new ptDNAs clearly show that, in contrast to parasitic algae, plastid genome compaction is not an obligatory route following the loss of photosynthesis in free-living algae, and that certain chlamydomonadalean algae have a remarkable propensity for genomic expansion, which can persist regardless of the trophic strategy. One sentence summary The plastid genomes of two free-living chlamydomonadalean algae, Hyalomonas oviformis and Hyalogonium fusiforme , reveal different evolutionary stages following the loss of photosynthesis.
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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".