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Roles of plant hormone signalling components in plant defence and susceptibility

Reference	BB/D018315/1
Principal Investigator / Supervisor	Professor Jonathan Jones
Co-Investigators / Co-Supervisors
Institution	University of East Anglia
Department	Sainsbury Laboratory
Funding type	Research
Value (£)	650,612
Status	Completed
Type	Research Grant
Start date	01/05/2006
End date	30/04/2009
Duration	36 months

Abstract

The elicitor bacterial flagellin (flg22) triggers reduced auxin sensitivity by inducing a microRNA (miR393) that targets an auxin receptor, TIR1. Overexpression of miR393 enhances bacterial resistance, and overexpression of a miR393-refractory paralog of TIR1 (AFB1) enhances disease. We will investigate how auxin promotes virulence, and how bacteria activate auxin signalling, by asking; 1- Do Arabidopsis mutants altered in auxin sensitivity or abundance show altered interactions with Pseudomonas syringae pv tomato DC3000 (PtoDC3000)? 2- Does altered auxin regulation affect sensitivity to other biotrophic and necrotrophic pathogens? 3- Does auxin affect defence responses such as the oxidative burst, callose deposition, kinase activation and ethylene (ET) and jasmonic acid (JA) synthesis and (using microarrays) differential gene regulation? 4- How does auxin promote bacterial disease sensitivity? (i) ARF transcription factors complex with AUX/IAA repressor proteins and bind to auxin-responsive promoters. There are 23 ARFs, for 18 of which T-DNA lines are available. We will test which ARF is involved in sensitivity to PtoDC3000 by examining mutants for enhanced resistance. (ii) Wild type and various auxin mutant leaves will be infiltrated with PtoDC3000 or PtoDC3000 hrcC mutants, and assayed over a detailed time course for defence gene expression. (iii) Auxin might activate JA signalling; we will measure JA levels and responses after auxin treatment, and test if bacterial sensitivity can be restored in 35S:miR393 lines by addition of JA. 5- PtoDC3000 does not make auxin; we will test if bacterial effector proteins trigger auxin signalling by comparing induction of auxin-responsive promoters to PtoDC3000 and to PtoDC3000 hrc mutants. 6- We will try to examine gene expression specifically in leaf L2 mesophyll cells by expressing a tagged ribosomal subunit using a Rubisco promoter, and affinity purifying polysomes with the tag for mRNA preparation.

Summary

For the Non Technical Summary, see the 'Revised objectives, costings, summary, technical summary ' document (uploaded 03/03/2006), under the 'Documents' tab.

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	Crop Science, Microbiology, Plant Science
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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