Characterization of a CYP81A in Triticum aestivum l. that endows natural herbicide tolerance

Allohexaploid bread wheat (Triticum aestivum L.) is one of the most widely cultivated crops globally and possesses natural tolerance to certain herbicides through rapid detoxification. Herbicide safeners, such as cloquintocet-mexyl (CM), are often applied in wheat to increase the expression of the genes encoding herbicide-detoxifying enzymes, which results in enhanced herbicide tolerance. One common wheat herbicide utilized with CM is the synthetic auxin, halauxifen-methyl (HM). Wheat esterases de-esterify HM to the biologically active form, halauxifen acid (HA), then cytochrome P450 monooxygenases (CYPs) rapidly detoxify HA to non-phytotoxic, polar metabolites. While the HA detoxification pathway in wheat has been established, the genes encoding the enzymes that catalyze these reactions have not been identified. Previous research utilizing wheat alien substitution and nullisomic-tetrasomic (NT) lines identified plants lacking chromosome 5A exhibited increased sensitivity to HM, indicating genes necessary for HA tolerance are located on this chromosome. To further characterize these lines, LC-MS is necessary to confirm the increased injury from HM is due to reduced rates or different pathways of HA detoxification. Furthermore, candidate genes can be identified and validated through molecular and phenotypic experimentation. Chapter 1 includes a literature review of CYP81A genes in wheat and other grass species, a description of clustered regularly interspaced short palindromic repeats (CRISPR)-editing, and the recent advances of CRISPR-editing in wheat. Chapter 2 describes LC-MS experiments to measure HA levels in the alien substitution and NT lines that previously displayed variable HM tolerance in greenhouse experimentation. These results indicate wheat lines lacking chromosome 5A have a reduced ability to detoxify HA, while lines possessing wheat chromosome 5A maintain the ability to detoxify HA. Experiments in Chapter 3 allowed for identification of a candidate CYP81A gene located on chromosome 5A (denoted as CYP81A-5A) and characterized CYP81A-5A as CM inducible but not HM inducible. Chapter 4 describes CRISPR-editing of CYP81A-5A to create progeny with a mutation in the promoter region. This mutant allele was inherited in a Mendelian fashion and had no effect on several developmental traits. However, progeny homozygous for the mutant allele displayed an increase in expression following CM treatment and increased tolerance to herbicide treatment relative to unedited wheat.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Landau, Olivia Augusta

Contributors dc:contributor

• Riechers, Dean E
• Moose, Stephen P
• Jamann, Tiffany M
• Lambert, Kris N

• Triticum Aestivum
• Cytochrome P450
• Synthetic Auxin
• Herbicide Metabolism

Statement dc:rights

• Copyright 2023 Olivia Landau

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/121487

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F121487