A putative 3‐hydroxyisobutyryl‐CoA hydrolase is required for efficient symbiotic nitrogen fixation in <i>Sinorhizobium meliloti</i> and <i>Sinorhizobium fredii</i> NGR234
Bibliographic record
Abstract
Summary We report that the smb20752 gene of the alfalfa symbiont Sinorhizobium meliloti is a novel symbiotic gene required for full N 2 ‐fixation. Deletion of smb20752 resulted in lower nitrogenase activity and smaller nodules without impacting overall nodule morphology. Orthologs of smb20752 were present in all alpha and beta rhizobia, including the ngr_b20860 gene of Sinorhizobium fredii NGR234. A ngr_b20860 mutant formed Fix − determinate nodules that developed normally to a late stage of the symbiosis on the host plants Macroptilium atropurpureum and Vigna unguiculata . However an early symbiotic defect was evident during symbiosis with Leucaena leucocephala , producing Fix − indeterminate nodules. The smb20752 and ngr_b20860 genes encode putative 3‐hydroxyisobutyryl‐CoA (HIB‐CoA) hydrolases. HIB‐CoA hydrolases are required for l ‐valine catabolism and appear to prevent the accumulation of toxic metabolic intermediates, particularly methacrylyl‐CoA. Evidence presented here and elsewhere (Curson et al ., , PLoS ONE 9:e97660) demonstrated that Smb20752 and NGR_b20860 can also prevent metabolic toxicity, are required for l ‐valine metabolism, and play an undefined role in 3‐hydroxybutyrate catabolism. We present evidence that the symbiotic defect of the HIB‐CoA hydrolase mutants is independent of the inability to catabolize l ‐valine and suggest it relates to the toxicity resulting from metabolism of other compounds possibly related to 3‐hydroxybutyric acid.
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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".