Plastidial starch phosphorylase regulates maltodextrin turnover during starch granule initiation in Arabidopsis leaves
Bibliographic record
Abstract
PLASTIDIAL STARCH PHOSPHORYLASE 1 (PHS1) is considered integral to starch synthesis, yet its role in transient starch synthesis in photosynthetic tissues remains unclear, as mutation of PHS1 in Arabidopsis (Arabidopsis thaliana) does not affect the metabolic profile of leaves. PHS1 activity is elevated in the starch branching enzyme sbe2.1 sbe2.2 double mutant, which lacks starch granules but retains intact genes encoding granule initiation proteins, making it an ideal plant material for exploring PHS1 function. We generated a triple mutant, sbe2.1 sbe2.2 phs1-1, which showed additional accumulation of soluble maltodextrins, a loss of insoluble linear α-glucans in the leaves, and substantially retarded plant growth, compared to the sbe2.1 sbe2.2 double mutant. STARCH SYNTHASE 3 (SS3) and SS4 activities increased in the sbe2.1 sbe2.2 phs1-1 triple mutant relative to the sbe2.1 sbe2.2 double mutant. Additional loss of SS4 in the sbe2.1 sbe2.2 phs1-1 background partially reversed phenotypes observed in the triple mutant: maltodextrin content decreased, insoluble α-glucans reappeared, and plant growth improved. Principal component analysis revealed that the metabolite profile of the sbe2.1 sbe2.2 ss4 and sbe2.1 sbe2.2 phs1-1 ss4 mutants, particularly the levels of organic acids from the tricarboxylic acid cycle, more closely resembled that of the wild type than that of sbe2.1 sbe2.2 and sbe2.1 sbe2.2 phs1-1. These findings suggest that PHS1 plays a critical role in maltodextrin turnover and carbon regulation in chloroplasts, maintaining a coordinated balance of synthetic and degradative activities. We propose that PHS1 functions as a metabolic buffer, with its role becoming more crucial when starch synthesis pathways are disrupted.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 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 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".