The <i>Populus</i> homeobox gene <i>ARBORKNOX2</i> regulates cell differentiation during secondary growth
Bibliographic record
Abstract
The stem cells of the vascular cambium divide to produce daughter cells, which in turn divide before undergoing differentiation during the radial growth of woody stems. The genetic regulation of these developmental events is poorly understood, however. We report here the cloning and functional characterization of a Populus class-I KNOX homeobox gene, ARBORKNOX2 (ARK2), which we show influences terminal cell differentiation and cell wall properties during secondary growth. In the early stages of secondary growth, ARK2 is expressed broadly in the cambial zone and in terminally differentiating cell types, before becoming progressively restricted to the cambium. ARK2 overexpression and synthetic miRNA-suppression transgenics reveal positive correlations between ARK2 expression level and the timing of cambium formation, the width of the cambial zone and inhibition of cambial daughter cell differentiation. These phenotypes in turn correlate with changes in the expression of genes affecting transcription, cell division, auxin and cell wall synthesis. Notably, wood properties associated with secondary cell wall synthesis are negatively associated with ARK2 expression, including lignin and cellulose content. Together, our results suggest that ARK2 functions primarily to regulate a complex suite of genes that together influence cell differentiation during secondary growth. We propose that ARK2 may represent a co-evolved transcriptional module that influences complex, adaptive wood properties.
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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".