Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha
The evolution of herbicide resistance in weeds is a threat to global crop yields. The aim of this thesis is to increase our understanding of the evolution and mechanisms of herbicide resistance. To achieve this, I first determine the phylogenetic relationships of both the ATP-binding cassette (ABC)...
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| Формат: | Дисертація |
| Мова: | English |
| Опубліковано: |
2023
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| _version_ | 1826312392778186752 |
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| author | Caygill, SG |
| author2 | Dolan, L |
| author_facet | Dolan, L Caygill, SG |
| author_sort | Caygill, SG |
| collection | OXFORD |
| description | The evolution of herbicide resistance in weeds is a threat to global crop yields. The aim of this thesis is to increase our understanding of the evolution and mechanisms of herbicide resistance. To achieve this, I first determine the phylogenetic relationships of both the ATP-binding cassette (ABC) transporter and uridine diphosphate glycosyltransferase (UGT) protein superfamilies within the Archaeplastida lineage. Proteins from these families confer non-target site resistance (NTSR) in populations of weeds. I also determine that the liverwort <em>Marchantia polymorpha</em> is naturally tolerant to the non-selective herbicide glyphosate. Using enzyme activity assays, I demonstrate that glyphosate tolerance in <em>M. polymorpha</em> is not due to a resistant version of the glyphosate target EPSPS. Instead, I discover a novel form of glyphosate tolerance conferred by the peptidoglycan biosynthesis enzyme MurA, which is structurally similar to EPSPS. By expressing MurA in the angiosperm <em>Arabidopsis thaliana</em> and generating <em>murA</em> loss-of-function mutants in <em>M. polymorpha</em>, I determine that MurA confers glyphosate tolerance independently from its function in peptidoglycan biosynthesis. I show that MpMurA catalyses the same reaction as EPSPS, transferring the enolpyruvyl moiety of phosphoenolpyruvate (PEP) to shikimate-3-phosphate (S3P) forming 5-enolpyruvylshikimate-3-phosphate (EPSP) product. However, like EPSPS, it is also inhibited by glyphosate. I therefore propose that MurA confers glyphosate tolerance either through a mechanism analogous to target-site overexpression or by binding glyphosate, making it less available to inhibit EPSPS. Through a metabolomic analysis, I also show that the metabolic response to glyphosate treatment in <em>M. polymorpha</em> differs from that in <em>A. thaliana</em>. This may be a result of, or contribute to, glyphosate tolerance in <em>M. polymorpha</em>. These results therefore demonstrate a novel form of glyphosate tolerance and determine the physiological impacts of glyphosate treatment that may contribute to its mode of action. |
| first_indexed | 2024-03-07T08:28:15Z |
| format | Thesis |
| id | oxford-uuid:d13c1f49-ac52-4aa7-bf34-d43a06b2a097 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:28:15Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:d13c1f49-ac52-4aa7-bf34-d43a06b2a0972024-02-23T09:31:29ZInvestigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorphaThesishttp://purl.org/coar/resource_type/c_db06uuid:d13c1f49-ac52-4aa7-bf34-d43a06b2a097Herbicide resistanceHerbicidesEvolutionEnglishHyrax Deposit2023Caygill, SGDolan, LThe evolution of herbicide resistance in weeds is a threat to global crop yields. The aim of this thesis is to increase our understanding of the evolution and mechanisms of herbicide resistance. To achieve this, I first determine the phylogenetic relationships of both the ATP-binding cassette (ABC) transporter and uridine diphosphate glycosyltransferase (UGT) protein superfamilies within the Archaeplastida lineage. Proteins from these families confer non-target site resistance (NTSR) in populations of weeds. I also determine that the liverwort <em>Marchantia polymorpha</em> is naturally tolerant to the non-selective herbicide glyphosate. Using enzyme activity assays, I demonstrate that glyphosate tolerance in <em>M. polymorpha</em> is not due to a resistant version of the glyphosate target EPSPS. Instead, I discover a novel form of glyphosate tolerance conferred by the peptidoglycan biosynthesis enzyme MurA, which is structurally similar to EPSPS. By expressing MurA in the angiosperm <em>Arabidopsis thaliana</em> and generating <em>murA</em> loss-of-function mutants in <em>M. polymorpha</em>, I determine that MurA confers glyphosate tolerance independently from its function in peptidoglycan biosynthesis. I show that MpMurA catalyses the same reaction as EPSPS, transferring the enolpyruvyl moiety of phosphoenolpyruvate (PEP) to shikimate-3-phosphate (S3P) forming 5-enolpyruvylshikimate-3-phosphate (EPSP) product. However, like EPSPS, it is also inhibited by glyphosate. I therefore propose that MurA confers glyphosate tolerance either through a mechanism analogous to target-site overexpression or by binding glyphosate, making it less available to inhibit EPSPS. Through a metabolomic analysis, I also show that the metabolic response to glyphosate treatment in <em>M. polymorpha</em> differs from that in <em>A. thaliana</em>. This may be a result of, or contribute to, glyphosate tolerance in <em>M. polymorpha</em>. These results therefore demonstrate a novel form of glyphosate tolerance and determine the physiological impacts of glyphosate treatment that may contribute to its mode of action. |
| spellingShingle | Herbicide resistance Herbicides Evolution Caygill, SG Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha |
| title | Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha |
| title_full | Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha |
| title_fullStr | Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha |
| title_full_unstemmed | Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha |
| title_short | Investigating glyphosate tolerance mechanisms in the liverwort Marchantia polymorpha |
| title_sort | investigating glyphosate tolerance mechanisms in the liverwort marchantia polymorpha |
| topic | Herbicide resistance Herbicides Evolution |
| work_keys_str_mv | AT caygillsg investigatingglyphosatetolerancemechanismsintheliverwortmarchantiapolymorpha |