Maintaining Methylation Activities during Salt Stress. The Involvement of Adenosine Kinase
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Bibliographic record
Abstract
Synthesis of the compatible osmolyte Gly betaine is increased in salt-stressed spinach (Spinacia oleracea). Gly betaine arises by oxidation of choline from phosphocholine. Phosphocholine is synthesized in the cytosol by three successive S-adenosyl-Met-dependent N-methylations of phosphoethanolamine. With each transmethylation, a molecule of S-adenosylhomo-Cys (SAH) is produced, a potent inhibitor of S-adenosyl-Met-dependent methyltransferases. We examined two enzymes involved in SAH metabolism: SAH hydrolase (SAHH) catabolizes SAH to adenosine plus homo-Cys and adenosine kinase (ADK) converts adenosine to adenosine monophosphate. In vitro SAHH and ADK activities increased incrementally in extracts from leaves of spinach plants subjected to successively higher levels of salt stress and these changes reflected increased levels of SAHH and ADK protein and transcripts. Another Gly betaine accumulator, sugar beet (Beta vulgaris), also showed salt-responsive increases in SAHH and ADK activities and protein whereas tobacco (Nicotiana tabacum) and canola (Brassica napus), which do not accumulate Gly betaine, did not show comparable changes in these enzymes. In spinach, subcellular localization positions SAHH and ADK in the cytosol with the phospho-base N-methyltransferase activities. Because SAHH activity is inhibited by its products, we propose that ADK is not a stress-responsive enzyme per se, but plays a pivotal role in sustaining transmethylation reactions in general by serving as a coarse metabolic control to reduce the cellular concentration of free adenosine. In support of this model, we grew Arabidopsis under a short-day photoperiod that promotes secondary cell wall development and found both ADK activity and transcript levels to increase severalfold.
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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 it