Investigation of calcium decoding mechanism during endosymbiosis in Medicago truncatula

Gobbato, Giulia (2024) Investigation of calcium decoding mechanism during endosymbiosis in Medicago truncatula. Doctoral thesis, University of East Anglia.

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Abstract

Legume roots interact with soil arbuscular mycorrhizal fungi and rhizobia to establish mutually beneficial symbioses, known as arbuscular mycorrhizal symbiosis and root nodule symbiosis. Molecular recognition of these symbionts by surface plasma membrane receptor-like kinases is essential for activating nuclear calcium oscillations, leading to the induction of endosymbiosis cellular reprogramming. The generation of the nuclear calcium signal requires the calcium channel encoded by the cyclic nucleotide-gated channel 15 (MtCNGC15) and DOES NOT MAKE INFECTION (MtDMI1), a non-selective cation channel. In this study, the analysis of a novel mutant allele of MtCNGC15, referred to as cngc15GOF, that is sufficient to enhance both root nodule symbiosis and arbuscular mycorrhizal (AM) symbiosis, was investigated. The gain-of-function (GOF) mutation in cngc15GOF is sufficient to auto-activate MtCNGC15, resulting in spontaneous nuclear calcium oscillations. This results in increased rhizobia infection, nodulation, and AM colonization. The spontaneous nuclear calcium oscillation has a lower frequency than the canonical symbiotic factor-induced calcium oscillation and is sufficient to modulate the expression of phenylpropanoid genes involved in the biosynthesis of flavonoids. These genes are modulated in response to the symbionts, indicating that the spontaneous nuclear calcium oscillations have a priming effect on their expression. Interestingly, the expression of the genes modulated by the spontaneous nuclear calcium oscillations is dependent on DOES NOT MAKE INFECTION 3 (MtDMI3), the putative decoder of the symbiotic factors-induced nuclear calcium oscillations. This further suggests that MtDMI3 can activate different transcriptional programs depending on the frequency of the calcium oscillations.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	17 Mar 2025 13:49
Last Modified:	17 Mar 2025 13:49
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98761
DOI:

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