Flavonol Biosynthesis Genes and Their Use in Engineering the Plant Antidiabetic Metabolite Montbretin A
Bibliographic record
Abstract
The plant metabolite montbretin A (MbA) and its precursor mini-MbA are potential new drugs for treating type 2 diabetes. These complex acylated flavonol glycosides only occur in small amounts in the corms of the ornamental plant montbretia (Crocosmia × crocosmiiflora). Our goal is to metabolically engineer Nicotiana benthamiana using montbretia genes to achieve increased production of mini-MbA and MbA. Two montbretia UDP-dependent glycosyltransferases (UGTs), CcUGT1 and CcUGT2, catalyze the formation of the first two pathway-specific intermediates in MbA biosynthesis, myricetin 3-O-rhamnoside and myricetin 3-O-glucosyl rhamnoside. In previous work, expression of these UGTs in N. benthamiana resulted in small amounts of kaempferol glycosides but not myricetin glycosides, suggesting that myricetin was limiting. Here, we investigated montbretia genes and enzymes of flavonol biosynthesis to enhance myricetin formation in N. benthamiana. We characterized two flavanone hydroxylases, a flavonol synthase, a flavonoid 3′-hydroxylase (F3′H), and a flavonoid 3′5′-hydroxylase (F3′5′H). Montbretia flavonol synthase converted dihydromyricetin into myricetin. Unexpectedly, montbretia F3′5′H shared higher sequence relatedness with F3′Hs in the CYP75B subfamily of cytochromes P450 than with those with known F3′5′H activity. Transient expression of combinations of montbretia flavonol biosynthesis genes and a montbretia MYB transcription factor in N. benthamiana resulted in availability of myricetin for MbA biosynthesis. Transient coexpression of montbretia flavonol biosynthesis genes combined with CcUGT1 and CcUGT2 in N. benthamiana resulted in 2 mg g−1 fresh weight of the MbA pathway-specific compound myricetin 3-O-glucosyl rhamnoside. Additional expression of the montbretia acyltransferase CcAT1 led to detectable levels of mini-MbA in N. benthamiana.
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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 | 0.001 |
| 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 | 0.001 | 0.001 |
| 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".