Glutamine Synthetase Mutations for Higher Plant Nitrogen Use
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Solution Overview
Problem
There is a need to improve nitrogen use efficiency in plants to enhance productivity and reduce input costs, particularly in maize and soybean production, where nitrogen fixation may become insufficient for high yields.
Innovation Solution
Introduction of glutamine synthetase (GS) polypeptides with specific amino acid mutations, encoded by polynucleotides, to enhance GS activity and increase nitrogen assimilation in plants, including recombinant DNA constructs and CRISPR-Cas endonuclease-mediated gene editing to introduce these mutations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nitrogen fixation is increased to meet high yield requirements, then productivity is improved, but the complexity of the symbiotic relationship and dependence on rhizobia increases
Solution Approach 1:
The plant is engineered to autonomously fix nitrogen through introduced nitrogen fixation genes, eliminating dependence on external rhizobia symbionts. The plant itself performs the nitrogen fixation function that previously required a complex symbiotic relationship, thereby simplifying the system while maintaining high yield capability.
Solution Approach 2:
The nitrogen fixation system is divided into separate functional components (nitrogen fixation genes, glutamine synthetase genes) that can be independently optimized and introduced into the plant genome, allowing modular improvement of nitrogen metabolism without requiring a complete symbiotic system.
2Productivity
If nitrogen fertilizer application is increased to improve yield, then productivity is improved, but the cost of inputs and environmental impact increases
Solution Approach 1:
The plant is equipped with endogenous nitrogen fixation capability through introduced genes, enabling it to produce its own nitrogen compounds independently of external fertilizer applications. This self-sufficiency reduces or eliminates the need for nitrogen fertilizer inputs while maintaining high productivity.
Solution Approach 2:
The nitrogen metabolism parameters of the plant are fundamentally altered by introducing nitrogen fixation genes and modifying glutamine synthetase activity, transforming the plant from a nitrogen-deficient system requiring external inputs to a nitrogen-sufficient system capable of autonomous nitrogen production.
3Productivity
If glutamine synthetase activity is increased to improve nitrogen use efficiency, then nitrogen assimilation is improved, but the complexity of genetic modification increases
Solution Approach 1:
The activity and properties of glutamine synthetase are optimized through site-directed mutagenesis of specific amino acid residues, changing the enzyme's kinetic parameters (Km, Vmax) to improve nitrogen assimilation efficiency. This targeted parameter optimization achieves enhanced nitrogen use efficiency through precise molecular modifications rather than complex systemic changes.
Solution Approach 2:
Specific amino acid residues at the active site of glutamine synthetase are modified to enhance catalytic efficiency, while the rest of the enzyme structure and the overall plant system remain unchanged. This localized modification approach improves nitrogen assimilation without requiring complex genome-wide modifications.
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
The modified GS polypeptides increase glutamine synthetase activity, leading to improved nitrogen use efficiency and higher seed protein content, thereby enhancing plant yield and reducing the need for nitrogen fertilizers.
Implementation Method 1
CRISPR-Cas endonuclease-mediated gene editing to introduce these mutations
Implementation Method 2
Ammonium is then assimilated into glutamine by the glutamine synthase-glutamate synthase system
Data Source
AI summary
Provided are compositions comprising polynucleotides encoding glutamine synthetase (GS) polypeptides having improved properties, such as increased enzymatic activity and/or increased thermostability. Also provided are recombinant DNA constructs, plants, plant cells, seed, grain comprising the polynucleotides. Additionally, various methods of employing the polynucleotides in plants, such as methods for increasing GS activity in a plant, methods for increase seed protein content in a seed of a plant, and methods for increasing yield of a plant, are also provided herein.