Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.743308
Title: Elicitation and evasion of plant innate immunity by beneficial and pathogenic bacteria
Author: Pfeilmeier, Sebastian
ISNI:       0000 0004 7227 3577
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2017
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Abstract:
Plasma membrane-localized pattern recognition receptors (PRRs) are central components of the plant innate immune system. PRRs perceive characteristic microbial features, termed pathogen-associated molecular patterns (PAMPs), leading to pattern-triggered immunity (PTI). As PAMPs from both pathogenic and beneficial bacteria are potentially recognized, both must employ strategies to evade and/or suppress PTI. Here, I show that exopolysaccharides (EPS) and flagella-driven motility, both of which are regulated by the secondary messenger cyclic-di-GMP, are important virulence factors at different stages during Pseudomonas syringae pv. tomato (Pto) DC3000 infection of Arabidopsis thaliana. High levels of cyclic-di-GMP impaired flagellin accumulation in different Pseudomonas species, and helped bacteria to evade recognition by the PRR FLAGELLIN SENSING 2. In this case, immune evasion was fully explained by the effect of cyclic-di-GMP on flagellin synthesis rather than on EPS production. Nevertheless, an EPS-deficient Pto DC3000 mutant, Δalg/psl/wss, showed compromised virulence, and a combination of two types of EPS appeared to be required for optimal in planta proliferation. In a complementary project, I tested whether PAMP recognition affects the interaction between the legume Medicago truncatula and its symbiotic partner Sinorhizobium meliloti. I transferred the PRR EF-TU RECEPTOR (EFR) from A. thaliana to M. truncatula, conferring recognition of the bacterial EF-Tu protein. Expression of EFR protected M. truncatula against the root pathogen Ralstonia solanacearum without compromising the overall symbiotic interaction with nitrogen-fixing S. meliloti. My results indicate that rhizobium either avoids PAMP recognition, or actively suppresses immune signalling during the infection process. Finally, I engineered a PAMP in S. meliloti by replacing the eliciting inactive flg22 epitope (derived from flagellin) with an eliciting epitope. My results suggest that legumes can be engineered with novel PRRs, as a biotechnological approach for broad-spectrum disease resistance, without perturbing the nitrogen-fixing symbiosis. Overall, my work contributes to our understanding of the molecular interaction between plants and bacteria.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.743308  DOI: Not available
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