Polyploid Genetic Engineering With Markerless Cre-LoxP Counter-Selection
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Solution Overview
Problem
Current genetic engineering methods for polyploid organisms, such as cyanobacteria, lack efficient shuttle vectors and counter-selection systems, making it difficult to modify nucleic acid sequences effectively due to challenges with replicative plasmids and existing markers like sacB, which are not suitable for organisms like Synechococcus sp. PCC 7002.
Innovation Solution
A system comprising nucleic acid constructs with site-specific recombination systems, such as Cre-LoxP, is used to integrate and excise genetic modifications in essential genes of polyploid organisms like Synechococcus sp. PCC 7002, utilizing natural counter-selection strategies to achieve markerless and full segregation of genetic modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional counter-selection markers like sacB are used, then counter-selection capability is provided, but the marker cannot be used in Synechococcus sp. PCC 7002 because the organism naturally produces sucrose as an osmolyte
Solution Approach 1:
The patent changes the chemical basis of counter-selection from sucrose polymerization (sacB) to osmotic stress utilization. By using a marker that exploits the host's natural osmolyte production mechanism, the system adapts to the specific physiological characteristics of Synechococcus sp. PCC 7002, allowing counter-selection in an organism that naturally produces sucrose.
Solution Approach 2:
The patent employs a counter-selection marker that utilizes the host organism's own natural physiological characteristics (sucrose production as osmolyte) against itself. The marker system leverages the host's endogenous osmotic stress response to achieve selection, eliminating the need for externally imposed incompatible markers.
2Adaptability or versatility
If broad-host range plasmids like RSF1010 are used, then host range is expanded, but the plasmids are difficult to transform into many host organisms and are very large (>10 kb)
Solution Approach 1:
The patent divides the genetic engineering system into separate functional components: a minimal replicon for maintenance, a transfer vector for delivery, and a counter-selection marker system. This segmentation allows each component to be optimized independently, reducing the overall complexity and size requirements compared to traditional broad-host-range plasmids.
Solution Approach 2:
The patent introduces an intermediary vector system that facilitates transformation. Rather than relying on the plasmid itself to directly transform the host, the system uses a specialized delivery mechanism that simplifies the transformation process and reduces the size requirements for successful host integration.
3Adaptability or versatility
If multiple steps and genetic parts are used for DNA modification, then modification capability is achieved, but the process becomes complex and time-consuming
Solution Approach 1:
The patent combines multiple functions into a single integrated system: the nucleic acid construct simultaneously provides the nucleic acid modification system, reporter genes for identification, and counter-selection marker capabilities. This merging eliminates the need for separate genetic parts and multiple sequential steps, streamlining the entire genetic engineering process.
Solution Approach 2:
The patent creates a universal genetic engineering system that can perform multiple functions through a single construct: DNA modification, identification of successful modification (via reporters), and counter-selection of unwanted modifications. This multi-functionality reduces the overall complexity by eliminating the need for multiple specialized tools and steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for efficient genetic modification of polyploid organisms without leaving behind antibiotic markers, reducing the complexity and time required for genetic engineering by exploiting polyploidy as an inherent counter-selection strategy.
Implementation Method 1
The first construct further comprises regions of homology to a first locus in an essential nucleic acid sequence in the organism flanking the nucleic acid modification system and the first reporter for integration of the first nucleic acid construct into the locus
Implementation Method 2
the first construct further encodes a site-specific recombination system having specificity for recombination recognition sequences
Data Source
AI summary
Compositions and methods for genetically modifying at least one nucleic acid sequence of interest in a polyploid organism.