Haploidy, Diploidy and Evolution of Antifungal Drug Resistance in Saccharomyces cerevisiae
Why this work is in the frame
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Bibliographic record
Abstract
We tested the hypothesis that the time course of the evolution of antifungal drug resistance depends on the ploidy of the fungus. The experiments were designed to measure the initial response to the selection imposed by the antifungal drug fluconazole up to and including the fixation of the first resistance mutation in populations of Saccharomyces cerevisiae. Under conditions of low drug concentration, mutations in the genes PDR1 and PDR3, which regulate the ABC transporters implicated in resistance to fluconazole, are favored. In this environment, diploid populations of defined size consistently became fixed for a resistance mutation sooner than haploid populations. Experiments manipulating population sizes showed that this advantage of diploids was due to increased mutation availability relative to that of haploids; in effect, diploids have twice the number of mutational targets as haploids and hence have a reduced waiting time for mutations to occur. Under conditions of high drug concentration, recessive mutations in ERG3, which result in resistance through altered sterol synthesis, are favored. In this environment, haploids consistently achieved resistance much sooner than diploids. When 29 haploid and 29 diploid populations were evolved for 100 generations in low drug concentration, the mutations fixed in diploid populations were all dominant, while the mutations fixed in haploid populations were either recessive (16 populations) or dominant (13 populations). Further, the spectrum of the 53 nonsynonymous mutations identified at the sequence level was different between haploids and diploids. These results fit existing theory on the relative abilities of haploids and diploids to adapt and suggest that the ploidy of the fungal pathogen has a strong impact on the evolution of fluconazole resistance.
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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 | 0.000 | 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 it