Transgenic Plants Using PCK and PPDK Enzymes for Nitrogen Remobilization
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Solution Overview
Problem
Current plant senescence processes result in the wastage of nitrogen present in senescent leaves, as it is not efficiently remobilized to younger parts of the plant, leading to reduced crop yields and nitrogen use efficiency.
Innovation Solution
Genetic constructs incorporating senescence-specific promoters linked to coding sequences encoding phosphoenolpyruvate carboxykinase (PCK) and pyruvate orthophosphate dikinase (PPDK) enzymes are introduced into plant cells to enhance nitrogen remobilization during leaf senescence, facilitating the transport of nitrogen from senescent leaves to other plant regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional plant senescence processes occur, then leaf cell death and chlorophyll loss proceed normally, but nitrogen and other nutrients remain trapped in senescent leaves and are not efficiently transported to younger plant parts
Solution Approach 1:
The patent introduces PEPCK and PPDK enzymes as intermediary substances that facilitate nitrogen remobilization. These enzymes act as mediators between the senescent leaf and the rest of the plant, converting nitrogen-containing compounds into transportable forms that can be moved to younger leaves and developing seeds, thereby preventing nitrogen loss while enhancing crop yield.
Solution Approach 2:
The patent changes the metabolic parameters of senescent leaves by overexpressing specific enzymes (PEPCK and PPDK). This alters the biochemical pathway in the senescent tissue, enabling active nitrogen remobilization instead of passive degradation. The parameter change transforms the senescence process from a nutrient-trapping state to a nutrient-transporting state, improving both nitrogen efficiency and crop yield.
2Quantity of substance
If nitrogen is not remobilized from senescent leaves, then simple leaf senescence occurs, but nitrogen use efficiency decreases and crop yield is reduced
Solution Approach 1:
The patent ensures the continuity of useful nitrogen utilization action by maintaining active nitrogen remobilization throughout the senescence process. The overexpressed PEPCK and PPDK enzymes continue to function from early to late senescence stages, ensuring that nitrogen is continuously converted into transportable forms and moved to productive plant parts, thereby preventing nitrogen loss and improving nitrogen use efficiency.
Solution Approach 2:
The patent enables the senescent leaf to serve itself by transforming from a nutrient-sinking organ to a nutrient-source organ. The overexpressed enzymes allow the senescent leaf to actively remobilize its own nitrogen content and transfer it to younger parts of the plant, making the senescence process beneficial rather than wasteful and improving overall nitrogen use efficiency.
3Productivity
If PEPCK and PPDK enzymes are over-expressed in senescent leaves, then nitrogen remobilization increases and crop yield improves, but the complexity of plant metabolism increases
Solution Approach 1:
The patent achieves multi-functionality by using the same PEPCK and PPDK enzymes for multiple purposes: they operate in both C3 and C4 plant metabolisms, function in both chloroplast and cytosol compartments, and serve dual roles in carbon metabolism and nitrogen remobilization. This universality allows the enzymes to improve crop yield without proportionally increasing metabolic complexity, as they are already present in the plant and simply overexpressed.
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 over-expression of PCK and PPDK enzymes in senescent leaves increases nitrogen remobilization, leading to enhanced vegetative growth and crop yields by efficiently transporting nitrogen to younger leaves and developing seeds.
Implementation Method 1
The enzymes phosphoenolpyruvate carboxykinase (PEPCK, or PCK) and pyruvate orthophosphate dikinase (PPDK) are known
Data Source
Figure 1(a)~1(e)
Figure 2a~2b
Figure 3a~3b
AI summary
The invention provides genetic constructs which comprise a senescence-specific promoter operably linked to at least one coding sequence, which encodes at least one polypeptide having phosphoenolpyruvate carboxykinase (PCK) activity and/or pyruvate orthophosphate dikinase (PPDK) activity.The constructs have the ability to cause, in transgenic plants, remobilisation of nitrogen during leaf senescence, such that nitrogen can be transported from the leaves to other regions of the plants. The invention provides plant cells and plants transformed with such constructs, methods of producing transgenic plants, and methods of increasing the rate of nitrogen remobilisation and growth rate in senescent plants. The invention also provides harvested plant leaves, such as tobacco leaves, that have been transformed with the genetic constructs, and to smoking articles comprising such harvested plant leaves.