Wheat MLO Gene Editing for Powdery Mildew Resistance
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Solution Overview
Problem
Hexaploid bread wheat is challenging to genetically modify due to its complex genome structure, making it difficult to develop resistance to powdery mildew disease, which is caused by Blumeria graminis f. sp. tritici, as existing methods struggle to mutate all three MLO homoeologs simultaneously and achieve stable, heritable disease resistance traits.
Innovation Solution
The use of CRISPR/Cas and TALEN systems for targeted genome editing to introduce loss-of-function mutations in all three TaMLO homoeologs (TaMLO-A1, TaMLO-B1, and TaMLO-D1) in wheat, enabling simultaneous mutation and stable transmission of these genes, thereby conferring broad-spectrum resistance to powdery mildew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If classical mutagenesis or transgenic approaches are used to mutate MLO genes in hexaploid wheat, then some MLO genes may be mutated, but it is difficult to mutate all three MLO homoeologs simultaneously and achieve stable heritable resistance
Solution Approach 1:
The patent applies segmentation by dividing the genome editing task into three separate TALEN constructs, each specifically targeting one of the three MLO homoeologs (MLO-A1, MLO-B1, MLO-D1). This allows simultaneous but distinct targeting of each gene copy, overcoming the redundancy problem in hexaploid wheat and achieving reliable disease resistance through coordinated mutation of all three segments.
2Productivity
If TALENs are designed to target conserved regions of MLO homoeologs, then editing efficiency across all three genes improves, but off-target effects may increase
Solution Approach 1:
The patent applies local quality by designing TALEN recognition sites that target locally conserved regions within each MLO homoeolog while incorporating species-specific variations. The TALEN constructs recognize 16-17 bp sequences separated by an 18 bp spacer, with careful selection of target sites that are conserved enough for efficient binding but specific enough to avoid off-target effects in the hexaploid genome.
3Reliability
If multiple TALEN constructs are introduced simultaneously, then all three MLO genes can be targeted, but transformation complexity and detection difficulty increase
Solution Approach 1:
The patent applies merging by combining three separate TALEN constructs into a single transformation system that can be introduced together. Each TALEN construct contains the necessary components (promoter, TALE repeat array, FokI nuclease domain) and can be co-transformed into wheat protoplasts or embryos, simplifying the overall process while achieving simultaneous targeting of all three MLO homoeologs.
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 successfully generates mutant wheat plants with broad-spectrum resistance to powdery mildew, demonstrating the first instance of mlo-mediated disease resistance in a polyploid plant, overcoming the limitations of classical mutagenesis and transgenic approaches.
Implementation Method 1
These techniques employ sequence-specific nucleases (SSNs) including zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the RNA-guided nuclease Cas9 (CRISPR/Cas9), which generate targeted DNA double-strand breaks (DSBs), which are then repaired mainly by either error-prone non-homologous end joining (NHEJ)
Data Source
AI summary
The present invention provides a mutant wheat plant resistant to powdery mildew and producing method thereof, wherein the mutant wheat plant comprises a loss of function mutation in a TaMLO-A1, TaMLO-B1 and TaMLO-D1 nucleic acid sequence. The present invention also provides a method for determining the presence or absence of a mutant TaMLO-A1, TaMLO-B1 and TaMLO-D1 nucleic acid or polypeptide in a wheat plant.