Characterization of Four Nuclear-Encoded Plastid RNA Polymerase Sigma Factor Genes in the Liverwort Marchantia polymorpha: Blue-Light- and Multiple Stress-Responsive SIG5 was Acquired Early in the Emergence of Terrestrial Plants
Bibliographic record
Abstract
The plastids of plant cells each contain their own genome, and a bacterial-type RNA polymerase called plastid-encoded plastid RNA polymerase (PEP) is involved in transcription of this genome. While the catalytic core subunits are encoded by the plastid genome, the specificity subunit of PEP, sigma, is generally encoded by the nuclear genome and imported into plastids from the cytoplasm after translation. In this study, we identified and analyzed four sigma factor genes from the nuclear genome of a liverwort, Marchantia polymorpha. Phylogenetic analysis suggested that three of the four genes were orthologous to vascular plant genes and thus they were named MpSIG1, MpSIG2 and MpSIG5. The remaining gene was named MpSIGX. The gene products were predicted to localize to the plastid, and this prediction was experimentally demonstrated by expressing yellow fluorescent protein fusion genes in vivo. As with SIG5 genes of other plant species, expression of MpSIG5 was induced by blue-light irradiation and also under various stress conditions, indicating that the regulatory mechanism responsible is conserved among divergent plant species. However, while the major role of SIG5 in vascular plants is to repair the damaged PSII reaction center through psbD gene transcription, the relevant blue-light-responsive promoter (psbD-BLRP) was not found in M. polymorpha and psbD transcript accumulation did not occur in conjunction with MpSIG5 induction. Thus, the physiological role of SIG5 is probably divergent among plant phyla.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".