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Title: Assessment of endosomes as sites of signal transduction in plants during bacterial attack
Author: Heard, William
ISNI:       0000 0004 5352 5249
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2014
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Endomembranes are integral to cellular function and particularly to plant defence. Environmental signals are perceived and immediate signalling responses are triggered from the PM, but how information is effectively transduced to generate the appropriate responses is less well understood. Furthermore the role of endosomes in implementing these responses is also not well understood. Outstanding questions are the importance of signalling by proteins from locations other than the PM and the relevance this has to overall signal transduction and how do endosomes contribute to defence. The work in this Ph. D.focussed on the understanding the role of endosome localised signalling proteins in response to detection of the bacterial PAMP flagellin and the corresponding proteome changes occurring in endosomes following detection of bacteria as part of defence responses. To understand and test the role of endosomes in defence characterised the proteomes of several endomembrane compartments including endosomes with an IP based method. Data obtained through this IP method is biologically relevant and simpler than other methods for preparation of endomembranes for proteomic analysis. The proteomic data was used to accurately predict the localisation of three members of the PRA1 RAB GTPase regulatory family of proteins. Furthermore this data was able to elucidate the differences in RFPRABF2b/ARA7 and RABF1/ARA6-RFP labelled LE/MVBs and their interaction with the TGN. Assessment of endosomal proteomes after flagellin treatment reveals a potential role for LE/MVB mediated secretion of flavonols in pathogen defence. Moreover, MPK cascade components were found in endosomal proteomes both before and after flagellin perception. Upon treatment, the flagellin responsive MPKs (MPK3, 4 and 6) were activated at endosomes and putative targets for phosphorylation by these MPKs identified. These data suggest endosomal signalling by MPKs occurs following flg22 treatment. Furthermore endosomal signalling is implicated in LE/MVB formation, cytoskeletal rearrangement and secretion of antimicrobial compounds.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available