Inhibition of 5’-methylthioadenosine metabolism in the Yang cycle alters polyamine levels, and impairs seedling growth and reproduction in Arabidopsis
Why this work is in the frame
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Bibliographic record
Abstract
The methionine or Yang cycle recycles Met from 5'-methylthioadenosine (MTA) which is produced from S-adenosyl-L-methionine (SAM) as a by-product of ethylene, polyamines, and nicotianamine (NA) synthesis. MTA nucleosidase is encoded by two genes in Arabidopsis thaliana, MTN1 and MTN2. Analysis of T-DNA insertion mutants and of wt revealed that MTN1 provides approximately 80% of the total MTN activity. Severe knock down of MTN enzyme activity in the mtn1-1 and mtn1-2 allelic lines resulted in accumulation of SAM/dSAM (decarboxylated SAM) and of MTA in seedlings grown on MTA as sulfur source. While ethylene and NA synthesis were not altered in mtn1-1 and mtn1-2 seedlings grown on MTA, putrescine and spermine were elevated. By contrast, mtn2-1 and mtn2-2 seedlings with near wt enzyme activity had wt levels of SAM/dSAM, MTA, and polyamines. In addition to the metabolic phenotypes, mtn1-1 and mtn1-2 seedlings were growth retarded, while seedlings of wt, mtn2-1, and mtn2-2 showed normal growth on 500 microm MTA. The double knock down mutant mtn1-1/mtn2-1 was sterile. In conclusion, the data presented identify MTA as a crucial metabolite that acts as a regulatory link between the Yang cycle and polyamine biosynthesis and identifies MTA nucleosidase as a crucial enzyme of the Yang cycle.
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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 | 0.001 | 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