Functional consequences of reductive protein evolution in a minimal eukaryotic genome
Bibliographic record
Abstract
Abstract Microsporidia are parasites with the smallest known eukaryotic genomes. The extent of protein loss in these organisms has been well documented, but much less is known about how compaction of microsporidia proteins affects their function. Taking a comparative genomic approach, we identified microsporidia orthologs of budding yeast proteins and show that these orthologs are enriched for essential yeast genes. We show that the median microsporidia protein is 21% shorter than its yeast counterpart and although extensive protein loss occurred after the divergence of microsporidia, reduced protein sizes were already present in microsporidian relatives. Microsporidia proteins are shorter through reduced domain lengths, diminished linker lengths, and domain loss, with 21% of microsporidia orthologs having lost domains present in yeast. On average, 34% of microsporidia orthologs have lost C-terminal residues essential for function in yeast, including 13 essential domains lost per genome. We also found that microsporidia display distinct phylogenetic patterns of domain loss, with losses occurring in a clade-specific manner. To investigate conservation of function, we used yeast complementation assays to test orthologs from several microsporidia species and their relative Rozella allomycis . These experiments reveal that most microsporidia proteins cannot complement their yeast orthologs, the ability to complement is about three-fold less than observed for R. allomycis orthologs, and proteins that do not complement are more reduced in length than their yeast orthologs. Altogether, our results demonstrate the drastic reduction of microsporidia proteins and show that these reductions have resulted in functional divergence from their fungal ancestors.
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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 | 0.001 |
| 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".