Extracellular <i>γ</i>-Aminobutyrate Mediates Communication between Plants and Other Organisms
Bibliographic record
Abstract
Plants exhibit mutually beneficial and antagonistic interactions with a variety of prokaryotic and eukaryotic organisms. We argue that these interactions are mediated in part by extracellular plant-derived γ-aminobutyrate (GABA). GABA is a ubiquitous four-carbon, nonprotein amino acid that is synthesized from Glu in a reaction catalyzed by the cytosolic enzyme Glu decarboxylase (GAD; Bown and Shelp, 1997; Shelp et al., 1999; Bouché and Fromm, 2004). It is noteworthy that plant GAD possesses a calmodulin (CaM)-binding domain that enables in vitro activity at pH 7.0 to 7.5 to be stimulated by the Ca2+/CaM complex. In contrast, activity at acidic pH values is unaffected by Ca2+/CaM and has a sharp pH optimum at 5.8. Subsequently, the GABA carbon is converted into succinic semialdehyde, and then to succinate, in reactions catalyzed by two mitochondrial enzymes, GABA transaminase and succinic semialdehyde dehydrogenase, respectively. In invertebrates (Sattelle, 1990) and vertebrates (Bormann, 2000), GABA is a potent inhibitory neurotransmitter. In plants, rapid GABA accumulation occurs in response to a variety of stresses (Bown and Shelp, 1997; Shelp et al., 1999; Kinnersley and Turano, 2000); however, the function(s) of that accumulation remains contentious. In many studies, accumulation results in the appearance of extracellular GABA, either in the apoplast or external medium (Secor and Schrader, 1985; Chung et al., 1992; Crawford et al., 1994; Solomon and Oliver, 2001). Extracellular GABA could result from exocytosis across the plasma membrane using a mechanism similar to that found in animal neurons (McIntire et al., 1997). In addition, wounding and associated disruption of cellular compartmentation release the acidic vacuolar contents to the cytosol, thereby activating GAD and stimulating GABA release from the wound to the external medium (Bown et al., 2006).
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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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".