Inflated organelle genomes and a circular-mapping mtDNA probably existed at the origin of coloniality in volvocine green algae
Why this work is in the frame
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Bibliographic record
Abstract
The volvocine lineage is a monophyletic grouping of unicellular, colonial and multicellular algae, and a model for studying the evolution of multicellularity. In addition to being morphologically diverse, volvocine algae boast a surprising amount of organelle genomic variation. Moreover, volvocine organelle genome complexity appears to scale positively with organismal complexity. However, the organelle DNA architecture at the origin of colonial living is not known. To examine this issue, we sequenced the plastid and mitochondrial DNAs (ptDNA and mtDNA) of the 4-celled alga Tetrabaena socialis, which is basal to the colonial and multicellular volvocines.Tetrabaena socialis has a circular-mapping mitochondrial genome, contrasting with the linear mtDNA architecture of its relative Chlamydomonas reinhardtii. This suggests that a circular-mapping mtDNA conformation emerged at or near the transition to group living in the volvocines, or represents the ancestral state of the lineage as a whole. The T. socialis ptDNA is very large (>405 kb) and dense with repeats, supporting the idea that a shift from a unicellular to a colonial existence coincided with organelle genomic expansion, potentially as a result of increased random genetic drift. These data reinforce the idea that volvocine algae harbour some of the most expanded plastid chromosomes from the eukaryotic tree of life. Circular-mapping mtDNAs are turning out to be more common within volvocines than originally thought, particularly for colonial and multicellular species. Altogether, volvocine organelle genomes became markedly more inflated during the evolution of multicellularity, but complex organelle genomes appear to have existed at the very beginning of colonial living.
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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 | 0.001 | 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) | 0.000 | 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 it