Resolving replication incompatibility between chloroplast and conjugative plasmids in <i>E. coli</i>
Bibliographic record
Abstract
ABSTRACT Chloroplast genomes present a promising chassis for engineering photosynthetic eukaryotes, but efficient delivery of large DNA constructs back into the organelle remains a major technical barrier. Conventional transformation methods rely on purified DNA and physical force to drive uptake into the chloroplast, often resulting in DNA shearing and thus low transfer efficiency for large constructs. Bacterial conjugation offers an attractive alternative as this is an entirely in vivo process, enabling DNA transfer without any physical manipulation. To assess the feasibility of this approach, we attempted to generate an Escherichia coli donor strain carrying both the broad-host-range conjugative plasmid pTA-Mob (52.7 kb) and the cloned Phaeodactylum tricornutum chloroplast genome (pPt_Cp, 132.9 kb). Unexpectedly, pTA-Mob and pPt_Cp proved incompatible: co-maintenance could not be achieved via electroporation, and conjugation with a self-transmissible pTA-Mob variant resulted in a ∼10□-fold decrease in transfer efficiency. Systematic testing of pTA-Mob and pPt_Cp plasmid variants as well as sequence analysis of evolved transconjugants revealed that the incompatibility arose from the pBBR1 replicon present in pTA-Mob. Guided by these insights, we identified an alternative conjugative plasmid, pRL443, that was compatible with pPt_Cp. Together, these findings provide a framework for dissecting plasmid incompatibility when working with large constructs and establish a functional conjugative system capable of mobilizing the P. tricornutum chloroplast genome.
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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 | 0.001 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 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".