Availability of carbon and nitrogen in soil affects Metarhizium robertsii root colonization and transfer of insect-derived nitrogen
Bibliographic record
Abstract
The endophytic, insect pathogenic fungus, Metarhizium, exchanges insect-derived nitrogen for photosynthate as part of a symbiotic association similar to well-known mycorrhizal relationships. However, little is known about this nitrogen transfer in soils where there is an abundance of nitrogen and/or carbon. Here, we applied D-glucose and ammonium nitrate to soil to examine the effect on root colonization and transfer of labelled nitrogen (15N) from an insect (injected with 15N-ammonium sulfate) to Metarhizium robertsii, into leaves of the common bean, Phaseolus vulgaris, over the course of 28 days. Application of exogenous carbon and/or nitrogen to soils significantly reduced detectable 15N in plant leaves. Metarhizium root colonization, quantified with real-time PCR, revealed colonization persisted under all conditions but was significantly greater on roots in soil supplemented with glucose and significantly lower in soil supplemented with ammonium nitrate. Fungal gene expression analysis revealed differential expression of sugar and nitrogen transporters (mrt, st3, nrr1, nit1, mep2) when Metarhizium was grown in pure broth culture or in co-culture with plant roots under various carbon and nitrogen conditions. The observation that Metarhizium maintained root colonization in the absence of nitrogen transfer, and without evidence of plant harm, is intriguing and indicates additional benefits with ecological importance.
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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) | 0.001 | 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 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".