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Investigating the role of autophagic cell death during plant infection by the rice blast fungus Magnaporthe grisea

Reference	BB/E022677/1
Principal Investigator / Supervisor	Professor Nicholas Talbot
Co-Investigators / Co-Supervisors
Institution	University of Exeter
Department	Biosciences
Funding type	Research
Value (£)	416,690
Status	Completed
Type	Research Grant
Start date	01/07/2007
End date	30/06/2010
Duration	36 months

Abstract

This project is based on the recent discovery that the rice blast fungus Magnaporthe grisea undergoes autophagic programmed cell death during plant infection (Veneault-Fourrey et al., 2006 Science 312: 580-83). The fungus infects rice plants using a specialised infection structure known as an appressorium which develops substantial turgor that is translated into physical force necessary to breach the tough outer cuticle of a rice leaf. Preliminary data is presented in the application to show that a mitotic division in the germ tube is necessary for appressorium morphogenesis and that this is coupled to initation of autophagic programed cell death of the fungal conidium. This project will define whether the cell cycle control point for appressorium development operates at the G2/M boundary or at the mitotic exit point, by inducible over-expression of the MgWEE1 kinase gene and alleles of the B-type cyclin genes lacking conserved destruction boxes necessary for degradation of B-type cyclins at the end of mitosis. The induction and spatio-temporal regulation of autophagic processes during infection-related development in M. grisea will be studied using a RFP-Atg8 gene fusion and by systematic gene deletion of autophagy-related genes. Cytological and ultrastructural analysis of infection cells in the resulting mutants will be carried out. Comparative transcriptional profiling will then be utilized to define the set of M. grisea genes associated with appressorium morphogenesis that also require induction of autophagy to have taken place. Real-time RT-PCR will be utilized to extend these predictions and study the temporal regulation of autophagy-related genes and appressorium morphogenetic genes. A sub-set of genes associated with appressorium functon ad penetration hypha development will be characterised in detail.

Summary

The aim of this project is to understand how rice plants become infected with a very serious disease called rice blast. Rice blast disease destroys up to 30% of the rice harvest each year and is a serious and recurrent threat to food security. We have discovered that the fungus that causes rice blast disease undergoes a form of programmed cell death that is necessary for it to bring about infection of a rice leaf. This project is designed to help us understand why a fungus undergoes this type of programmed suicide of its spores, in order to allow its specialised infection structures to function correctly. The project is significant because new control strategies are urgently required for rice blast disease. Fungicides are expensive and resistance to them can develop very rapidly. More durable control methods, either based on chemical intervention or resistance breeding, require a knowledge of the biology of the fungal agent responsible for this devastating disease. A large international community is studying rice blast because of its economic and social importance. Because of this, the genome of the fungus has been sequenced and many tools have been developed to study the fungus genetically. This provides a significant opportunity to learn more about fundamental biology of plant disease, but in a disease of international significance. The rice blast fungus is also similar to many of the fungi that cause disease on crops grown widely in the UK such as wheat and barley and its infection strategy is very similar to that of powdery mildews and rusts, for example. Knowledge gained from this project may therefore also benefit UK agriculture.

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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