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Genetic dissection of receptor-mediated susceptibility and molecular cloning of the matching ligand(s) from the pathogen

Reference	BB/D000750/1
Principal Investigator / Supervisor	Professor Mahmut Tör
Co-Investigators / Co-Supervisors	Professor Eric Holub, Dr alison tor
Institution	University of Warwick
Department	Warwick HRI
Funding type	Research
Value (£)	265,329
Status	Completed
Type	Research Grant
Start date	01/11/2005
End date	31/07/2009
Duration	45 months

Abstract

We have cloned the RPP27 gene, an RLP that confers downy mildew resistance in Arabidopsis and are in the process of identifying the genetic requirements of RPP27-mediated resistance. We have also identified another RLP, RPP30, which confers resistance to Peronospora isolate Cala2, adding further proof that the perception of Peronospora by Arabidopsis is at the plasma membrane by receptor like proteins. Recently, we have shown that RPP27 can provide enhanced susceptibility in Columbia (Col-0) Arabidopsis to some avirulant isolates including Cala2, Cand5 and Hind4 but not to Hind2 and Emoy2. This indicates that for these three isolates receptor-like protein, RPP27, may mediate susceptibility and that in the case of Cala2, the effector molecule recognised by the RPP27 suppresses RPP30-RPP2A and RPP2B-mediated defence response. We believe this is a novel and exciting discovery and presents a unique opportunity to study how susceptibility and resistance may be linked and how susceptibility can arise from the innate immune system of plants. The first part of the proposed research is to identify genetic requirements of susceptibility. The second part is to identify the map location of effector molecules (ATR proteins) that are recognised by RPP27 and clone the ATR that triggers susceptibility. Following identification of the ATR proteins, studying the interaction between RPP27 and the ATR protein would be the immediate objective. It will also help to understand how the signal is transmitted from extracellular region into the cytoplasmic region of the cell.

Summary

In a natural environment, a wide range of parasites including viruses, bacteria, fungi and nematodes routinely challenge plants and try to exploit them as a source of food. Plants have an innate immune system to detect and defend themselves against these potential invaders. It has been long accepted that the interaction of a resistance (R) gene in the plant and an avirulence (Avr) gene in the pathogen activates the defence system in the plant. In addition, absence of either of these genes (R or Avr) has been assumed to lead to infection by the pathogen. Recently we have cloned a receptor-like protein (RLP) from Arabidopsis designated as RPP27 that confers resistance to the downy mildew pathogen Peronospora parasitica, a biotrophic parasite closely related to Phytophthora infestans (potato late blight). Within the last year, we have shown that this RLP encoding gene RPP27 also provides susceptibility instead of resistance to some other isolates of P. parasitica. This clearly shows that in this case infection by a pathogen is not due to the lack of an R-gene but can be mediated by the cell surface receptor proteins. This is a novel discovery and the aim of the proposed project is to utilise the resources in Arabidopsis and Peronospora to investigate how this RLP protein mediates the susceptibility. The project will involve a multidisciplinary approach by scientists at Warwick HRI that will deliver excellent internationally competitive science.

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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