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Title: Encoding of calcium signals in innate immunity and development
Author: Leitao, Jose
ISNI:       0000 0004 7227 6647
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2018
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Calcium (Ca2+) is a widely used second messenger in eukaryotes. Spatially-restricted and temporary variations in the concentration of Ca2+ in the cytosol or the nucleus mediate various physiological responses. This is the case of the pathways that control innate immunity or symbiosis in plants. In the first case, a cytosolic Ca2+ burst occurs upon pathogen perception and is required for the production of reactive oxygen species (ROS). A plasma membrane-localised channel is predicted to mediate this signal, but so far has not been identified. In the second, the Ca2+ oscillations required for establishment of rhizobial and arbuscular mycorrhizal symbioses occur in the nucleus. In Medicago truncatula, these are mediated by the potassium-permeable channel DOES NOT MAKE INFECTIONS 1 (DMI1) and the cyclic nucleotide-gated channels (CNGC) 15a/b/c. These genes are conserved in non-symbiotic species, which suggests additional roles for nuclear Ca2+ signalling. In this work, I screened a collection of Ca2+ channel mutants for ROS production upon perception of flg22, the immunogenic peptide of bacterial flagellin and an activator of innate immunity. This led to the identification of a triple mutant in the glutamate receptor-like family, glr3.1glr3.3aglr3.6a, which had a decreased ROS production and reduced induction of the defence gene NHL10, upon treatment with flg22. Furthermore, using a Ca2+ sensor that allows distinction between nuclear and cytosolic Ca2+, I showed that nuclear Ca2+ oscillations, dependent on AtDMI1 and AtCNGC15, occur during normal root growth in Arabidopsis. dmi1 and cngc15 mutants had defects in root development, due to perturbations in endogenous auxin levels. For the first time, nuclear Ca2+ oscillations were linked to auxin-mediated signalling and a key developmental process in a non-symbiotic species. This thesis highlights the dynamic complexity of Ca2+ signalling and the impact that understanding the mechanisms of Ca2+ influx can have in defence and development. Keywords: Calcium, influx, CNGC, GLR, DMI1, defence, root development, auxin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available