Characterization of Cytochrome P450s with Key Roles in Determining Herbicide Selectivity in Maize

Area of Science:

• Agricultural Science
• Biochemistry
• Plant Science

Background:

• Safeners are crucial for herbicide selectivity in maize, primarily by inducing detoxifying enzymes like cytochrome P450 monooxygenases (CYPs).
• Understanding these safener-inducible CYPs is vital for optimizing herbicide use in this globally significant crop.

Purpose of the Study:

• To identify and characterize safener-inducible CYPs responsible for herbicide metabolism in maize.
• To investigate the substrate specificity and functional plasticity of key CYP enzymes involved in herbicide detoxification.

Main Methods:

• Employed transcriptomics, proteomics, and functional assays in yeast to identify and analyze CYP enzyme activity.
• Utilized quantitative transcriptomics and proteomics to determine dominant enzymes in field and sweet corn.
• Constructed recombinant chimeras of CYP81A2 and CYP81A9 to investigate structure-activity relationships.

Main Results:

• Identified 18 safener-induced CYPs across clans 71, 72, 74, and 86.
• Herbicide metabolism was predominantly linked to CYP81A family members (CYP81A9, CYP81A16, CYP81A2) from clan 71.
• CYP81A9 exhibited broad activity against multiple herbicide chemistries, while CYP81A2 specifically hydroxylated bentazon; substrate specificity plasticity was localized in CYP81A9's N-terminal region.

Conclusions:

• Maize CYP81A9 and CYP81A16 are dominant enzymes in safener-treated field maize, with CYP81A9 also prominent in sweet corn.
• The CYP81A family, particularly CYP81A9, plays a significant role in determining herbicide selectivity in maize.
• Phylogenetic analysis suggests a conserved function for clan 71 CYPs in agrochemical metabolism across cereals and wild grasses.