Enzymes of choline synthesis in diverse plants: variation in phosphobase <i>N</i>-methyltransferase activities
Bibliographic record
Abstract
S-adenosyl-L-methionine dependent phospho-base N-methyltransferases are involved in the sequential methylations of phosphoethanolamine [Formula: see text] phosphomethylethanolamine [Formula: see text] phosphodimethylethanolamine [Formula: see text] phosphocholine. Phosphocholine is a precursor for the ubiquitous phospholipid phosphatidylcholine and for free choline, which can be oxidized to produce the osmoprotectant glycine betaine. Despite the importance of these enzymes to growth and stress tolerance, their activities have been studied in comparatively few plant species. Phospho-base N-methylating activities were assayed in leaf extracts prepared from 17 diverse plant species. All plants tested can perform the first step ( N-methylation of phosphoethanolamine) with in vitro activity rates varying from 0.13 nmol·min1·g1 fresh weight for soybean (Glycine max (L.) Merr.) and pea (Pisum sativum L.) to 25 nmol·min1·g1 fresh weight for cotton (Gossypium hirsutum L.). Of the plant species surveyed, only soybean and pea showed no capacity to perform the two subsequent N-methylation steps. Exposing plants to prolonged dark periods led to decreased phosphoethanolamine N-methylating activity relative to light-exposed controls with the extent of decrease varying among the species from 30% (Limonium perezii (Stapf) F.T. Hubb) to over 90% (Spinacia oleracea L., Beta vulgaris L., and Amaranthus caudatus L.). Thus, light-responsive properties and levels of phosphobase methyltransferase activities vary among plants with a trend towards higher activities being found in plants that accumulate glycine betaine.Key words: glycine betaine, choline, phosphatidylcholine, phosphocholine.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".