High light enhances the expression of low‐CO<sub>2</sub>‐inducible transcripts involved in the CO<sub>2</sub>‐concentrating mechanism in <i>Synechocystis</i> sp. PCC6803
Bibliographic record
Abstract
ABSTRACT The relative abundances of key gene transcripts encoding proteins involved in inducible inorganic carbon (Ci) transport in the cyanobacterium Synechocystis PCC6803 were quantified by real‐time reverse‐transcriptase‐polymerase chain reaction under conditions of varying Ci and light levels. Significant increases in CO2‐concentrating mechanism (CCM)‐related transcript abundance were observed only in cells aerated with CO2‐free air for 30 min in the light, but not in the dark, relative to illuminated cells grown at high CO2 levels (high‐Ci cells). Cells were incubated under precisely defined conditions in a cuvette attached to a mass spectrometer to allow for the measurement of photosynthetic gas exchange rates, [Ci] and [O2], in combination with quantitative analysis of transcripts. Under conditions of increasing irradiance and low [Ci], or under conditions of decreasing [Ci] at constant irradiance, the abundances of cmpA (encoding part of the BCT1 HCO3– transporter), ndhF3 (encoding subunit of high‐affinity CO2 uptake system) and sbtA (encoding Na+‐dependent HCO3– transporter) transcripts tended to increase, relative to illuminated cells grown at high‐CO2. The cmpA transcript appeared to be less responsive to decreasing [Ci] than either ndhF3 or sbtA. The induction of cmpA and ndhF3 transcripts was completely inhibited by 10 µm 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) compared to untreated control cells. This inhibitor had no effect on sbtA expression. In the presence of 2,6‐dichlorobenzoquinone (DCBQ), the expression of the cmpA transcript tracked the apparent rate of O2 evolution from photosystem II closely as the irradiance was increased, reaching maximum levels of expression approximately 16‐fold higher than control cells. Under the same conditions, the ndhF3 transcript increased by two‐ to three‐fold, whereas the sbtA transcript did not respond to this treatment. The regulation of CCM induction in this strain is discussed in relation to current hypotheses on the sensing of Ci limitation.
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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) | 0.001 | 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".