Herbicide-resistant 4-hydroxyphenylpyruvate dioxygenase variants identified via directed evolution

Area of Science:

• Agricultural Science
• Biochemistry
• Genetics

Background:

• Herbicides are vital for crop production, but herbicide-resistant weeds and crop susceptibility limit their effectiveness.
• 4-hydroxyphenylpyruvate dioxygenase (HPPD) is a key enzyme targeted by β-triketone herbicides like mesotrione.
• Developing herbicide resistance in crops is crucial for sustainable agriculture.

Purpose of the Study:

• To identify mutations in the cotton HPPD gene conferring resistance to mesotrione.
• To understand the impact of these mutations on HPPD enzymatic activity and plant function.
• To explore the potential for developing herbicide-resistant cotton varieties.

Main Methods:

• Established a high-throughput mutant screening system in Escherichia coli.
• Identified single nucleotide changes in the cotton HPPD gene leading to amino acid substitutions.
• Tested the enzymatic activity and complementation ability of HPPD variants in Arabidopsis.

Main Results:

• Four single nucleotide changes conferring mesotrione resistance were identified, preserving native HPPD activity.
• Combinations of these mutations showed synergistic effects on herbicide resistance.
• HPPD variants successfully complemented the Arabidopsis athppd mutant and enhanced herbicide resistance in transgenic plants.

Conclusions:

• Specific mutations in the cotton HPPD gene can confer significant mesotrione resistance.
• These resistant HPPD variants retain sufficient native activity for plant growth.
• Findings provide a basis for gene editing strategies to develop herbicide-resistant cotton.