Frog-killing chytrid fungus deploys different strategies to regulate intracellular pressure in developmental states that have or lack a cell wall
Bibliographic record
Abstract
Cell morphogenesis is crucial for the physiology of animals and fungi alike. While animals typically shape their cells using the actin cytoskeleton, fungi control cell shape through polarized deposition of new cell-wall material, which is inflated by intracellular osmotic "turgor" pressure. Understanding where and when these mechanisms evolved is essential for understanding cell morphogenesis evolution. To this end, we study chytrid fungi, which have a cell type that lacks a cell wall (the "zoospore") and a cell type that has a cell wall (the "sporangium"). While chytrid sporangia rely on polarized cell-wall growth to control shape, we previously showed that the "frog-killing" chytrid fungus Batrachochytrium dendrobatidis uses actin to control zoospore shape. Whether either zoospores or sporangia also use intracellular pressure regulation in cell-shape control remains an open question. We use live-cell imaging, environmental perturbations, and small-molecule inhibitors to show that B. dendrobatidis sporangia generate and maintain turgor pressure, whereas B. dendrobatidis zoospores use specialized organelles called contractile vacuoles to pump water out of the cell, thereby keeping internal pressure low. Because chytrid fungi diverged prior to the evolution of the Dikarya-the fungal group including yeasts, mushrooms, and filamentous fungi-these findings suggest that turgor pressure evolved early and that cell morphogenesis underwent a major transition during early fungal evolution. We also suggest that the last common fungal ancestor may have, like chytrid fungi, employed stage-specific strategies for cell-shape control-illustrating how developmental flexibility in cellular mechanisms can serve as a wellspring of evolutionary innovation.
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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".