HPPD Polypeptide Mutations for Herbicide Tolerance
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Solution Overview
Problem
Current HPPD inhibitor herbicides exhibit slow-binding or slow, tight-binding properties, making it difficult to develop plants with full tolerance against structurally diverse HPPD inhibitor herbicides, as mutations that reduce inhibitor affinity do not completely overcome inhibition due to long-lasting binding.
Innovation Solution
Development of HPPD polypeptides with reduced affinity to HPPD inhibitor herbicides and increased dissociation rates, converting slow-binding inhibitors into fully reversible inhibitors, allowing for broad tolerance against various chemical classes of HPPD herbicides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mutations are introduced to reduce inhibitor affinity, then herbicide tolerance is improved, but inhibition duration is prolonged due to slow dissociation rates
Solution Approach 1:
The patent applies parameter changes by modifying specific amino acid residues (Gly336Trp, Pro215Leu, Gly336Ile, Gly336Ala) in the HPPD enzyme to alter the binding kinetics parameters. These mutations change the affinity and dissociation rate constants, converting slow-binding inhibitors into fully reversible inhibitors with faster dissociation, thereby achieving both high tolerance and short inhibition duration.
2Reliability
If HPPD enzyme expression is increased to overcome inhibition, then herbicide tolerance is improved, but metabolic burden on the plant increases
Solution Approach 1:
Instead of increasing enzyme expression levels, the patent changes the kinetic parameters of the HPPD enzyme through specific mutations. The mutated enzyme has altered affinity and dissociation characteristics that provide tolerance without requiring increased expression, thereby avoiding the metabolic burden associated with overexpression strategies.
3Reliability
If slow-binding inhibitors are used to achieve potent herbicidal activity, then herbicide effectiveness is improved, but development of tolerant plants becomes more difficult
Solution Approach 1:
The patent inverts the traditional approach by not trying to overcome slow-binding inhibition through conventional means (increased expression or affinity reduction alone), but instead by modifying the enzyme to achieve fast dissociation. This inversion allows the use of potent slow-binding inhibitors while still developing tolerant plants, as the mutated enzyme rapidly releases the inhibitor.
Solution Approach 2:
The patent changes the binding kinetics parameters of the HPPD enzyme through specific amino acid mutations, transforming the enzyme's interaction with slow-binding inhibitors. This parameter change enables the enzyme to rapidly dissociate from inhibitors, maintaining herbicide effectiveness while achieving plant tolerance.
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 HPPD polypeptides achieve high levels of inhibitor tolerance by reducing affinity and increasing dissociation rates, enabling plants to withstand multiple classes of HPPD inhibitor herbicides without prolonged inhibition, thus providing enhanced agricultural applications.
Implementation Method 1
The 4-hydroxyphenylpyruvate dioxygenases (HPPDs) are enzymes which catalyze the reaction in which para-hydroxyphenylpyruvate (abbreviated herein as HPP), a tyrosine degradation product, is transformed into homogentisate (abbreviated herein as HGA)
Implementation Method 2
Some molecules which inhibit HPPD (hereinafter named HPPD inhibitor herbicides), and which inhibit transformation of the HPP into HGA while binding specifically to the enzyme
Implementation Method 3
HPPD polypeptides with reduced affinity to HPPD inhibitor herbicides and increased dissociation rates, converting slow-binding inhibitors into fully reversible inhibitors
Data Source
AI summary
In the present invention, HPPD polypeptides and plants containing them showing a full tolerance against one or more HPPD inhibitor herbicides belonging to various chemical classes are described. A set of mutant HPPD polypeptides have been designed which have either no or only a significantly reduced affinity to HPPD inhibitor herbicides and, at the same time, the rate of dissociation of the HPPD inhibitors of the mutant HPPD polypeptide is increased to such an extent that the HPPD inhibitors no longer act as slow-binding or slow, tight-binding inhibitors but, instead of this, have become fully reversible inhibitors. In particular, isolated polynucleotides encoding mutant HPPD polypeptides conferring tolerance to HPPD inhibitor herbicides belonging to various chemical classes are provided. Additionally, amino acid sequences corresponding to the polynucleotides are encompassed.