Palmelloid formation in the Antarctic psychrophile, Chlamydomonas priscuii, is photoprotective
Bibliographic record
Abstract
Cultures of the obligate, Antarctic psychrophile, Chlamydomonas priscuii grown at permissive low temperature (8°C) are composed of flagellated, single cells, as well as non-motile, multicellular palmelloids. The relative proportions of the two cell types are temperature dependent. However, the temperature dependence for palmelloid formation is not restricted to psychrophilic C. priscuii but appears to be a general response of mesophilic Chlamydomonas species (C. reinhardtii and C. raudensis) to non-permissive growth temperatures. To examine potential differences in photosynthetic performance between single cells versus palmelloids of the psychrophile, a cell filtration technique was developed to separate single cells from palmelloids of C. priscuii grown at 8°C. Flow cytometry was used to estimate the diameter of isolated single cells (≤5 μm) versus isolated palmelloids of varying size (≥8 μm). Compared to single cells, palmelloids of C. priscuii showed a decrease in the abundance of light-harvesting complex II (LHCII) proteins with a 2-fold higher Chl a/b ratio. A decrease in both lutein and β-carotene in palmelloids resulted in carotenoid pools which were 27% lower in palmelloids compared to single cells of the psychrophile. Chlorophyll fluorescence analyses of the isolated fractions revealed that maximum photochemical efficiency of PSII (Fv/Fm) was comparable for both single cells and palmelloids of C. priscuii. However, isolated palmelloids exhibited lower excitation pressure, measured as 1 - qL, but higher yield of PSII (ΦPSII) and 50% higher rates of electron transport (ETR) than single cells exposed to high light at 8°C. This decreased sensitivity to high light in isolated palmelloids compared to single cells was associated with greater non-regulated dissipation of excess absorbed energy (ΦNO) with minimal differences in ΦNPQ in C. priscuii in response to increasing irradiance at low temperature. The ratio ΦNO/ΦNPQ observed for isolated palmelloids of C. priscuii developed at 8°C (1.414 ± 0.036) was 1.38-fold higher than ΦNO/ΦNPQ of isolated single cells (1.021 ± 0.018) exposed to low temperature combined with high light (1,000 μmol m−2 s−1). The differences in the energy quenching capacities between palmelloids and single cells are discussed in terms of enhanced photoprotection of C. priscuii palmelloids against low-temperature photoinhibition.
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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) | 0.000 | 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 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".