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ETHYLENE SIGNALING INCREASES REACTIVE OXYGEN SPECIES THAT DRIVE ROOT DEVELOPMENT VIA OXIDATION OF TARGET PROTEINS

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title
ETHYLENE SIGNALING INCREASES REACTIVE OXYGEN SPECIES THAT DRIVE ROOT DEVELOPMENT VIA OXIDATION OF TARGET PROTEINS
author
Martin, Rachel Emily
abstract
The plant hormone, ethylene, and its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), induce root hair development in Arabidopsis thaliana. This process is governed by the ETR1 ethylene receptor, and the master regulators of ethylene-induced transcription, EIN3 and EIL1. Reactive oxygen species (ROS) can also act as signaling molecules to drive developmental changes, including root hair initiation and elongation, so this dissertation examined whether ethylene increased localized ROS accumulation to drive this process. Root hairs form from epidermal cells on the root surface, and form in alternating patterns so that each hair-forming cell (trichoblast) is adjacent to a non hair-forming cell (atrichoblast). Confocal microscopy paired with redox-sensitive biosensors and dyes revealed that treatments that elevate ethylene increased ROS accumulation in trichoblast cells prior to root hair formation, but did not alter ROS levels in atrichoblast cells. This effect is lost in the ethylene receptor and transcription factor mutants, etr1-3 and ein3eil1. ACC treatment increased the transcript levels and activity of ROS-producing enzymes, Respiratory Burst Oxidase Homolog C (RBOHC), and the class III peroxidase, PRX44, and this response was lost in ein3eil1. Ethylene-induced ROS synthesis is also reduced in rbohc and prx44 mutants. Signaling-induced ROS can regulate protein structure and/or activity by oxidizing cysteine thiol residues to cysteine sulfenic acids, which is a reversible reaction that can act as a molecular switch regulating enzyme activity. To identify oxidative targets that may drive root hair formation, we generated two unique redox proteomic datasets to identify proteins in roots of Col-0 that contain a cysteine sulfenic acid modification. We employed both a targeted method, involving the use of the cysteine sulfenic acid specific probe, DCP-Bio1, and a global redox proteomics approach to identify proteins with cysteine sulfenic acid modifications. We found 7 PRX genes that show this reversible oxidative modification and tested the functional role of the oxidizable cysteine in one of these proteins. Together these results reveal biochemical mechanisms by which the plant hormone ethylene can increase ROS levels, ROS can then alter protein oxidation state and activity, and drive root hair formation.
subject
class III peroxidase
ethylene
NADPH oxidase
reactive oxygen species
root hair
contributor
Muday, Gloria K (advisor)
Hollis, Thomas (committee member)
Poole, Leslie B (committee member)
Esstman, Sarah M (committee member)
Reid, Ke Z (committee member)
date
2023-09-08T08:35:25Z (accessioned)
2023 (issued)
degree
Biochemistry and Molecular Biology (discipline)
embargo
2024-09-07 (terms)
2024-09-07 (liftdate)
identifier
http://hdl.handle.net/10339/102618 (uri)
language
en (iso)
publisher
Wake Forest University
type
Dissertation

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