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Burgess, Jodie (2025) Exploring the role of A. thaliana DIOXYGENASE FOR AUXIN OXIDATION 1 and 2 in optimising root architecture and its evolutional origin. PhD thesis, University of Nottingham.

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Abstract

The plant hormone auxin plays a key role in almost every aspect of plant growth and development, including environmental adaptive responses. Cellular auxin levels are tightly regulated by the interplay between homeostasis, signalling and transport. Regulation creates a cell-to-cell gradient of auxin, which dependent on tissue and developmental context, is translated into developmental outputs. A fundamental way cellular auxin levels are regulated is by auxin degradation. Primarily conjugation to amino acids, which are then oxidised by two enzymes in Arabidopsis thaliana named DIOXYGENASE FOR AUXIN OXIDATION 1 and 2 (AtDAO1 and 2).

This work aims to understand how AtDAO1 and AtDAO2, and ultimately auxin degradation, contribute to adapting root architecture to environmental stress. Auxin helps optimise root architecture to maximise resource acquisition while limiting the impact of increasingly common abiotic stresses. AtDAO1 and AtDAO2 knock out and overexpression lines were subject to low water and high salinity environments, which are increasingly common with our changing climate, to establish differences in growth, development, and gene expression. Phenotypic and molecular analyses under osmotic and salinity stress revealed that DAOs play a limited role in auxin homeostasis under optimal conditions but are crucial for stress adaptation. AtDAO2 had a distinct role in osmotic stress, and a newly identified spliced AtDAO1 variant increases abundance during stress response. The changes in root architecture and gene expression were proven to be driven by stress rather than direct changes in auxin levels. Phylogenetic analysis then corroborated the evolutionary conservation of DAO-like domains across higher plant species, with divergence of AtDAO1 and AtDAO2 occurring within the eudicots.

Understanding how auxin gradients form to regulate cell differentiation will provide important insight into basic plant development and identify targets for crop breeding programmes. This research ultimately aims to support sustainable agriculture practices, stable food production, and to help mitigate the adverse effects of environmental stressors.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Voss, Ute
Keywords:	Auxin; Cellular auxin levels; Auxin degradation; Auxin gradients; Plant development
Subjects:	Q Science > QK Botany
Faculties/Schools:	UK Campuses > Faculty of Science > School of Biosciences
Item ID:	81598
Depositing User:	Burgess, Jodie
Date Deposited:	31 Dec 2025 04:40
Last Modified:	31 Dec 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/81598

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