The regulation of nitrate and ammonium transport systems in plants
Bibliographic record
Abstract
Inorganic nitrogen concentrations in soil solutions vary across several orders of magnitude among different soils and as a result of seasonal changes. In order to respond to this heterogeneity, plants have evolved mechanisms to regulate \({\mathrm{NO}_{3}^{{-}}}\) and \({\mathrm{NH}_{4}^{{+}}}\) influx. In addition, efflux analysis using 13N has revealed that there is a co-ordinated regulation of all component fluxes within the root, including biochemical fluxes. Physiological studies have demonstrated the presence of two high-affinity transporter systems (HATS) for \({\mathrm{NO}_{3}^{{-}}}\) and one HATS for \({\mathrm{NH}_{4}^{{+}}}\) in roots of higher plants. By contrast, in Arabidopsis thaliana there exist seven members of the NRT2 family encoding putative HATS for \({\mathrm{NO}_{3}^{{-}}}\) and five members of the AMT1 family encoding putative HATS for \({\mathrm{NH}_{4}^{{+}}}\) . The induction of high-affinity \({\mathrm{NO}_{3}^{{-}}}\) transport and Nrt2.1 and Nrt2.2 expression occur in response to the provision of \({\mathrm{NO}_{3}^{{-}}}\) , while down-regulation of these genes appear to be due to the effects of glutamine. High-affinity \({\mathrm{NH}_{4}^{{+}}}\) transport and AMT1.1 expression also appear to be subject to down-regulation by glutamine. In addition, there is evidence that accumulated \({\mathrm{NO}_{3}^{{-}}}\) and \({\mathrm{NH}_{4}^{{+}}}\) may act post-transcriptionally on transporter function. The present challenge is to resolve the functions of all of these genes. In Aspergillus nidulans and Chlamydomonas reinhardtii there are but two high-affinity \({\mathrm{NO}_{3}^{{-}}}\) transporters and these appear to have undergone kinetic differentiation that permits a greater efficiency of \({\mathrm{NO}_{3}^{{-}}}\) absorption over the wide range of concentration normally found in nature. Such kinetic differentiation may also have occurred among higher plant transporters. The characterization of transporter function in higher plants is currently being inferred from patterns of gene expression in roots and shoots, as well as through studies of heterologous expression systems and knockout mutants.
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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 | 0.000 | 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 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".