Evolution of the Glucose-6-Phosphate Isomerase: The Plasticity of Primary Metabolism in Photosynthetic Eukaryotes
Bibliographic record
Abstract
Glucose-6-phosphate isomerase (GPI) has an essential function in both catabolic glycolysis and anabolic gluconeogenesis and is universally distributed among Eukaryotes, Bacteria, and some Archaea. In addition to the cytosolic GPI, land plant chloroplasts harbor a nuclear encoded isoenzyme of cyanobacterial origin that is indispensable for the oxidative pentose phosphate pathway (OPPP) and plastid starch accumulation. We established 12 new GPI sequences from rhodophytes, the glaucophyte Cyanophora paradoxa, a ciliate, and all orders of complex algae with red plastids (haptophytes, diatoms, cryptophytes, and dinoflagellates). Our comprehensive phylogenies do not support previous GPI-based speculations about a eukaryote-to-prokaryote horizontal gene transfer from metazoa to gamma-proteobacteria. The evolution of cytosolic GPI is largely in agreement with small subunit analyses, which indicates that it is a specific marker of the host cell. A distinct subtree comprising alveolates (ciliates, apicomplexa, Perkinsus, and dinoflagellates), stramenopiles (diatoms and Phytophthora [oomycete]), and Plantae (green plants, rhodophytes, and Cyanophora) might suggest a common origin of these superensembles. Finally, in contrast to land plants where the plastid GPI is of cyanobacterial origin, chlorophytes and rhodophytes independently recruited a duplicate of the cytosolic GPI that subsequently acquired a transit peptide for plastid import. A secondary loss of the cytosolic isoenzyme and the plastid localization of the single GPI in chlorophycean green algae is compatible with physiological studies. Our findings reveal the fundamental importance of the plastid OPPP for Plantae and document the plasticity of primary metabolism.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".