GA20 Oxidase Gene Editing for Semi-Dwarf Corn Without Off-Types
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Solution Overview
Problem
Existing methods have failed to achieve increased yield and lodging resistance in corn plants through manipulation of the gibberellin pathway due to associated off-types and reproductive issues, such as masculinization and sterility, which have hindered the development of semi-dwarf, high-yielding corn varieties.
Innovation Solution
Modifying corn plants with targeted mutations at the GA20 oxidase_3 and GA20 oxidase_5 loci, specifically through genome editing to introduce homozygous and heterozygous mutations, resulting in reduced plant height, increased stem diameter, and improved lodging resistance without reproductive off-types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If GA pathway genes are mutated to reduce plant height, then lodging resistance is improved, but reproductive abnormalities occur and yield decreases
Solution Approach 1:
The patent divides the GA pathway manipulation into two separate target genes (GA20ox1 and GA20ox3) rather than mutating a single gene. This segmentation allows for more precise control of gibberellin levels, achieving reduced plant height and improved lodging resistance while avoiding the severe reproductive abnormalities that occur with single-gene mutations in traditional approaches.
Solution Approach 2:
The patent changes the parameter of GA pathway manipulation from complete gene knockout to controlled reduction of gibberellin biosynthesis activity. By using CRISPR/Cas9 to create partial loss-of-function mutations in GA20ox1 and GA20ox3, the patent achieves intermediate GA levels that maintain reproductive normality while still providing the semi-dwarf phenotype needed for improved lodging resistance.
2Strength
If GA pathway genes are mutated to reduce plant height, then lodging resistance is improved, but yield decreases
Solution Approach 1:
By targeting two specific GA biosynthesis genes (GA20ox1 and GA20ox3) rather than the entire GA pathway, the patent segments the manipulation to achieve precise control over plant height without severely impacting yield. This segmented approach allows maintenance of adequate GA levels for reproductive processes while achieving the semi-dwarf phenotype for improved lodging resistance and yield potential.
Solution Approach 2:
The patent changes the parameter from complete gene inactivation to partial function reduction, creating a balance where plant height is sufficiently reduced for improved lodging resistance and yield, but GA levels remain adequate for normal reproduction and grain filling. This parameter optimization resolves the contradiction between lodging resistance and yield maintenance.
3Reliability
If traditional breeding methods are used to develop semi-dwarf corn, then reproductive off-types occur, but with genome editing these off-types are eliminated
Solution Approach 1:
The patent replaces traditional mechanical breeding methods (crossing, selection, and repeated backcrossing) with genome editing technology (CRISPR/Cas9). This substitution eliminates the need for multiple generations of breeding to eliminate off-types, as the desired mutations can be directly introduced with high precision, achieving reproductive normality without the complexity of traditional breeding programs.
Solution Approach 2:
The patent uses the CRISPR/Cas9 system to copy the desired mutation pattern from model systems (where GA pathway manipulation successfully produced semi-dwarf varieties) into corn. By copying the successful strategy of targeting GA20ox genes from other cereal crops and adapting it to corn's specific genome, the patent achieves similar success without the reproductive off-types that plagued traditional breeding attempts.
Data Source
AI summary
The present disclosure provides compositions and methods for the editing or mutating of specific subtypes of GA20 oxidase genes and specific zygosity combinations of those edits or mutations. Modified plants, and plant parts and cells thereof, having mutations reducing the expression or activity of GA20 oxidase genes are further provided with improved characteristics, such as reduced plant height and increased lodging resistance, but without off-types. Methods are further provided for making modified plants, and plant parts and cells thereof, having one or more mutations in specific subtypes of GA20 oxidase genes.