Tertiary Endosymbiosis in Two Dinotoms Has Generated Little Change in the Mitochondrial Genomes of Their Dinoflagellate Hosts and Diatom Endosymbionts
Bibliographic record
Abstract
BACKGROUND: Mitochondria or mitochondrion-derived organelles are found in all eukaryotes with the exception of secondary or tertiary plastid endosymbionts. In these highly reduced systems, the mitochondrion has been lost in all cases except the diatom endosymbionts found in a small group of dinoflagellates, called 'dinotoms', the only cells with two evolutionarily distinct mitochondria. To investigate the persistence of this redundancy and its consequences on the content and structure of the endosymbiont and host mitochondrial genomes, we report the sequences of these genomes from two dinotoms. METHODOLOGY/PRINCIPAL FINDINGS: The endosymbiont mitochondrial genomes of Durinskia baltica and Kryptoperidinium foliaceum exhibit nearly identical gene content with other diatoms, and highly conserved gene order (nearly identical to that of the raphid pennate diatom Fragilariopsis cylindrus). These two genomes are differentiated from other diatoms' by the fission of nad11 and by an insertion within nad2, in-frame and unspliced from the mRNA. Durinskia baltica is further distinguished from K. foliaceum by two gene fusions and its lack of introns. The host mitochondrial genome in D. baltica encodes cox1 and cob plus several fragments of LSU rRNA gene in a hugely expanded genome that includes numerous pseudogenes, and a trans-spliced cox3 gene, like in other dinoflagellates. Over 100 distinct contigs were identified through 454 sequencing, but intact full-length genes for cox1, cob and the 5' exon of cox3 were present as a single contig each, suggesting most of the genome is pseudogenes. The host mitochondrial genome of K. foliaceum was difficult to identify, but fragments of all the three protein-coding genes, corresponding transcripts, and transcripts of several LSU rRNA fragments were all recovered. CONCLUSIONS/SIGNIFICANCE: Overall, the endosymbiont and host mitochondrial genomes in the two dinotoms have changed surprisingly little from those of free-living diatoms and dinoflagellates, irrespective of their long coexistence side by side in dinotoms.
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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 | 0.000 | 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 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".