Encoding and decoding nuclear Calcium signalling in plant root development and Endosymbiosis

Tipper, Emily Caroline (2023) Encoding and decoding nuclear Calcium signalling in plant root development and Endosymbiosis. Doctoral thesis, University of East Anglia.

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Abstract

Calcium ions (Ca2+)are used as secondary messengers across eukaryotes. The encoding and decoding of each calcium signal is vital to maintain its fidelity and specificity. In Medicago truncatula, nuclear calcium oscillations are required for root endosymbioses with arbuscular mycorrhizal (AM) fungi and rhizobia bacteria. In Arabidopsis thaliana, nuclear calcium releases in the root apical meristem are required for normal primary root development. In both cases, these nuclear calcium releases are generated by the calcium ion channel CNGCJK and the counter cation channel DMIJ. In this thesis, their regulation is studied in both species separately.

Heterotrimeric G protein signalling has been implicated in root legume symbioses with Gβ acting as a positive regulator of nodulation in soybean. Here, I identify an interactor of Medicago Gβ, APSRJ, that is required for proper AM colonisation and is regulated by phosphate at the transcript level, suggesting that it is involved in the regulation of AM endosymbiosis by phosphate.

In Arabidopsis thaliana, using a combination of homology modelling, and electrophysiology, I show that the mutation of a highly conserved aspartic acid in the C-linker domain is sufficient to impair the gating of AtCNCGJK. This is the first time the C-linker region of a plant CNGC has been implicated in channel gating. In addition, I show that in the presence of nitrate AtCNGCJK relocalises to the plasma membrane specifically in the columella cells. I hypothesise that the induction of primary nitrate response genes, such as
LBD89, LBD8:, and LBD8;, is modulated by different inputs of cytoplasmic or nuclear calcium release. Finally, I identify the EF-hand containing protein RSAJ as a potential decoder of the nuclear calcium release in Arabidopsis root apical meristems.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Nicola Veasy
Date Deposited:	26 Jun 2024 14:33
Last Modified:	26 Jun 2024 14:33
URI:	https://ueaeprints.uea.ac.uk/id/eprint/95695
DOI:

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