Mitochondrial alternative oxidase, reactive oxygen species and programmed cell death in Nicotiana tabacum
Bibliographic record
Abstract
Programmed cell death (PCD) is an integral component of many plant biological processes including senescence, xylem differentiation and as a response to both biotic and abiotic stresses. Understanding how PCD functions in plants will lead to better understanding of these important biological processes. Unlike animal PCD, plant PCD has not been well studied and as such, the mechanisms of plant PCD pathways and their regulation remain unclear. The mitochondrion is known to play an important role in the activation and regulation of many animal PCD pathways; however, the role of the mitochondrion in plant PCD is poorly understood. It could differ from that in animals, for example, due to the existence of additional electron transport chain components. One such component is the alternative oxidase (AOX), which represents a branch of the mitochondrial electron transport chain that accepts electrons from ubiquinol and catalyzes the reduction of oxygen to water. Interestingly, we found that AOX influenced the level of cellular reactive oxygen species (ROS), which strongly correlated with susceptibility to cell death induced by well-known hypersensitive response (HR)-associated signaling molecules including salicylic acid, hydrogen peroxide and nitric oxide. Investigations into the mechanisms of cell death versus those of defense pathway activation revealed that the cellular ROS level is an important determinant of the defensive threshold of the cell, which when breached, leads to PCD activation. Interestingly, our findings suggest that the mitochondrion plays a significant role in the activation of defense and death pathways through its ability to both define cellular ROS level and modulate the chemical nature and intensity of a mitochondrial-derived ROS signal. An integrative model which summarizes the role of the mitochondrion, the chemical nature of ROS signal produced, and the impact of the antioxidant network on the decision between life and death is presented. Overall, the concept that the plant can modulate death in response to the severity of the stress seems simple; however, this ability provides the plant with a great deal of flexibility to respond appropriately to an ever changing environment and may represent a basic physiological response to diverse abiotic and biotic stresses.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".