Investigating the mechanisms of nuclear calcium oscillations during rhizobial infection in Medicago truncatula endosymbiosis.

Bridge, Edmund (2024) Investigating the mechanisms of nuclear calcium oscillations during rhizobial infection in Medicago truncatula endosymbiosis. Doctoral thesis, University of East Anglia.

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Abstract

The legume Medicago truncatula establishes a symbiotic relationship with nitrogen-fixing rhizobia, which are internalized within root nodules structures to facilitate effective nitrogen fixation. A key early signal in this interaction is the generation of nuclear calcium oscillations in the root epidermis, triggered by the perception of bacterial Nodulation (Nod) factors. These calcium signals are critical for rhizobial infection and initiating nodule formation. Bacteria are transported to the developing nodule primordia by infection threads (ITs), which traverse the cortical tissue and ultimately release rhizobia into specific cells within the nodule. Nuclear calcium oscillations continue to control the IT progression within the outer cortical tissues. The indeterminate nodules of M. truncatula possess a continuously active apical meristem, giving them a conical shape with distinct developmental zones from tip to base. In the infection zone in the nodule apex, ITs continue to proliferate, releasing rhizobia into plant cells, where they differentiate into nitrogen-fixing bacteroids. Although components involved in the nuclear calcium signalling are expressed in the nodule apex, nothing is known about the role of these oscillations during nodule infection.

This thesis characterises a novel component in the root nodule symbiosis signalling pathway. A mutant allele causing premature termination of nuclear calcium oscillations and defective bacterial release in the nodule infection zone raises questions about the role of calcium oscillations in the nodule apex. Furthermore, this study investigates interactions between this component and the nuclear membrane localised ion channel DOES NOT MAKE INFECTIONS 1 (DMI1) as well as the calcium decoder DOES NOT MAKE INFECTIONS 3 (DMI3), and uses RNA sequencing to investigate the downstream effects of the mutant allele in root nodule symbiosis.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	James Tweddle
Date Deposited:	18 Feb 2025 12:34
Last Modified:	18 Feb 2025 12:34
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98533
DOI:

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