Molecular and Cellular Analysis of Zinc Homeostasis and its Interaction with Auxin in Arabidopsis thaliana

Gate, Thomas (2022) Molecular and Cellular Analysis of Zinc Homeostasis and its Interaction with Auxin in Arabidopsis thaliana. Doctoral thesis, University of East Anglia.

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Zinc (Zn) is an essential micronutrient in all organisms. Auxin (IAA) is a major plant hormone, co-ordinating growth and development. Transport of Zn between the endoplasmic reticulum (ER) and cytosol in plant cells is proposed to be important for the systemic Zn deficiency response and the activation of auxin amino acid conjugates. This thesis aims to increase understanding of how ER Zn transport is controlled and how it impacts wider Zn and auxin homeostasis.

Metal tolerance protein 2 (AtMTP2) was shown to transport Zn into the ER in Zn deficient conditions. Reporter plants expressing AtMTP2 promotor-controlled luciferase were generated and AtMTP2 was shown to be specifically induced in Zn deficiency. These reporter plants will be used in future forward genetic screens to find regulatory elements that control Zn ER import in Zn deficiency.

IAA-Alanine resistant 1 (AtIAR1) has previously been identified as a likely ER metal transporter that when mutated led to insensitivity to IAA-Alanine as a result of a hypothesised build-up of metal ions in the ER. In this work, AtIAR1 was shown to transport Zn, likely not only out of the ER, but also Golgi. One mutant found in the screen, Atiar1-3, still showed Zn transport, but reduced trafficking in yeast assays.

Both the Atiar1-3 mutant and a suspected knockout Atiar1-t mutant were tested for disrupted response to Zn deficiency and excess conditions but showed mostly developmental phenotypes. Testing of auxin-related developmental phenotypes in these two Atiar1 mutants enabled the discovery of an excess Zn - exogenous auxin interaction that was partially AtIAR1 dependant. In addition, the two Atiar1 mutants were found to differ in severity and time dependence of their phenotypes. Both mutants showed altered IAA conjugation and enhanced skotomorphogenesis. Overall, this work demonstrates a role for ER/Golgi Zn homeostasis in wider auxin-related development.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 19 Jun 2023 13:46
Last Modified: 19 Jun 2023 13:46

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