Characterisation of potential regulators of PAMP-triggered immunity

Niebergall, Roda (2012) Characterisation of potential regulators of PAMP-triggered immunity. Doctoral thesis, University of East Anglia.

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An essential part of plant innate immunity is the perception of pathogen-associated molecular patterns (PAMPs) through surface-localised pattern-recognition receptors (PRRs). EFR and FLS2 are well characterised PRRs, which recognise the bacterial elongation factor Tu and flagellin, respectively. A variety of downstream responses upon PAMP perception have been described. However, it is still poorly understood how EFR- and FLS2-dependent signalling is mediated. Here, I used two different approaches in order to identify novel components of both signalling pathways.
First, I characterised seven candidate genes of a predicted flagellin-dependent gene expression network, which are predicted to regulate each other’s expression in a flagellin-dependent manner, and therefore, are potentially involved in the FLS2 signalling pathway. Further characterisation revealed that mutation of at least three of the seven candidate genes was affecting flg22-mediated signalling.
In addition, I characterised a predicted protein phosphatase 2C (PP2C), which had been identified in a yeast two-hybrid screen with the EFR cytoplasmic domain and was therefore referred to as PIE (PP2C-interacting with EFR). Using Co-IP experiments, I confirmed that PIE associates with EFR in planta. Furthermore, PIE also associates with FLS2 and BIK1, a co-regulator of both PRRs, in planta. Interestingly, PIE dissociates from both the EFR and FLS2 complexes upon PAMP perception. PIE expressed in planta and in E. coli exhibits protein phosphatase activity and we showed that PIE dephosphorylates EFR, FLS2 and BIK1 in vitro. As expected from bio-informatic predictions, I confirmed that PIE is phosphorylated upon PAMP perception. Furthermore, I demonstrated that EFR and FLS2 kinase activities are partially required for PIE phosphorylation. Both PIE overexpression and pie knock-down lines display reduced PAMP-triggered responses, indicating that an optimal PIE expression level is required for proper induction of signalling. All together, these results imply that PIE is a novel regulator of the EFR and FLS2 signalling pathway.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Users 2259 not found.
Date Deposited: 02 May 2013 13:28
Last Modified: 31 Jan 2016 01:38

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