Respiratory and C <sub>4</sub> -photosynthetic NAD-malic enzyme coexist in bundle sheath cells mitochondria and evolved via association of differentially adapted subunits
Bibliographic record
Abstract
ABSTRACT In different lineages of Cleomaceae, NAD-malic enzyme (NAD-ME) was independently co-opted to participate in C 4 photosynthesis. In the C 4 Cleome species Gynandropsis gynandra and Cleome angustifolia, all NAD-ME genes ( NAD-MEα, NAD-MEβ1, and NAD-MEβ2 ) were affected by C 4 evolution and are expressed at higher levels than their orthologs in the C 3 Cleome species Tarenaya hassleriana . In the latter C 3 species, the NAD-ME housekeeping function is performed by two heteromers, NAD-MEα/β1 and NAD-MEα/β2, with similar biochemical properties. In both C 4 species analyzed, this role is restricted the NAD-MEα/β2 heteromer. In the C 4 species, NAD-MEα/β1 is exclusively present in the leaves, where it accounts for most of the enzymatic activity. GgNAD-MEα/β1 exhibits high catalytic efficiency and is differentially activated by the C 4 intermediate aspartate, confirming its role as the C 4 -decarboxylase. During C 4 evolution, GgNAD-MEβ1and CaNAD-MEβ1 lost their catalytic activity; their contribution to enzymatic activity results from a stabilizing effect on the associated α-subunit. We conclude that in bundle sheath cell mitochondria of C 4 Cleome species, the functions of NAD-ME as C 4 photosynthetic decarboxylase and as a tricarboxylic acid cycle-associated housekeeping enzyme coexist and are performed by isoforms that combine the same α subunit with differentially adapted β subunits.
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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) | 0.001 | 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 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".