VirD2-Mutant Agrobacterium for Transient T-DNA Transfer
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Solution Overview
Problem
Existing Agrobacterium strains integrate T-DNA into the plant genome during transformation, leading to transgenic plants, which are subject to regulation, making genome editing in plants with long generation times or vegetatively propagated species economically infeasible.
Innovation Solution
Development of Agrobacterium strains with VirD2 mutants that facilitate efficient transient transformation while reducing or eliminating stable integration, using nucleotide substitutions, insertions, and deletions to create strains like 4E12, ExD3, 1B10, and others, which support transient GUS activity and low stable transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Agrobacterium strains transfer T-DNA into plants, then genome editing reagents are delivered efficiently, but T-DNA integrates into the plant genome creating transgenic plants subject to regulation
Solution Approach 1:
The patent extracts and removes the integration function from the T-DNA delivery system by using VirD2 mutants that can transfer T-DNA but cannot integrate it into the plant genome. This separates the useful function (delivery of genome editing reagents) from the harmful function (creation of transgenic plants), allowing efficient genome editing without regulatory burden.
Solution Approach 2:
The patent changes the molecular parameters of the VirD2 protein through specific mutations (e.g., in the ω domain, NLS, or other regions) to alter its function. These parameter changes disable the integration capability while preserving the transfer capability, transforming the system from creating stable transgenic plants to enabling transient genome editing only.
2Productivity
If Agrobacterium strains use wild-type VirD2 for T-DNA transfer, then transformation efficiency is high, but stable integration occurs which is not desirable for certain applications
Solution Approach 1:
The patent modifies specific parameters of the VirD2 protein through targeted mutations in key domains (ω domain, NLS, tyrosine residue, etc.) to change its functional properties. These parameter changes reduce or eliminate integration efficiency while maintaining transfer efficiency, achieving the desired decoupling of these two functions.
Solution Approach 2:
The patent applies local quality changes by introducing mutations at specific locations within the VirD2 protein sequence (such as the C-terminal ω domain or NLS regions) rather than altering the entire protein. This localized modification approach allows selective disruption of the integration function while preserving the transfer function.
3Ease of operation
If genetic crossing is used to eliminate T-DNA after genome editing, then non-transgenic plants are obtained, but this is not practical for plants with long generation times or vegetative propagation
Solution Approach 1:
The patent performs preliminary action by using Agrobacterium strains with VirD2 mutants that prevent T-DNA integration from the start. This eliminates the need for subsequent genetic crossing to remove T-DNA, as the T-DNA never becomes stably integrated into the plant genome in the first place, saving significant time especially for plants with long generation times.
Solution Approach 2:
The patent extracts the integration capability from the transformation process, allowing genome editing reagents to be delivered and function transiently without creating permanent transgenic plants. This eliminates the need for time-consuming breeding programs to eliminate transgenes.
Data Source
AI summary
The present disclosure provides a series of mutant Agrobacterium strains generated by random mutagenesis of a wide-type or ω mutant VirD2 gene or VirD2 protein. The mutant Agrobacterium strains of the present disclosure transiently express T-DNA-encoded transgenes in a target plant but do not stably integrate these genes into the plant genome.