ARS | Publication request: RECEPTOR-LIGAND INTERACTIOS IN CONTROL OF RICE BLAST DISEASE

Submitted to: International Congress on Molecular Plant-Microbe Interactions
Publication Type: Abstract Only
Publication Acceptance Date: July 20, 2001
Publication Date: N/A

Technical Abstract: Pi-ta-mediated resistance in rice controls strains of the rice blast fungus, Magnaporthe grisea, that express avirulent alleles of AVR-Pita in a gene-for-gene manner. Pi-ta is a single-copy resistance gene of the NBS- LRR class. AVR-Pita encodes an infection-specific protein predicted to function as a neutral zinc metalloprotease based on homology searches and on the occurrence of an amino acid sequence motif characteristic for these proteases. Current data suggest that the Pi-ta protein is an intracellular receptor that binds to the putative mature form of the AVR-Pita protease inside the plant cell, initiating defense responses. This model raises interesting questions on the nature of the plant-fungal interface for intracellular infection hyphae, and on the mechanism by which the fungus delivers proteins into the cytosol of healthy plant cells. We are analyzing structure-function relationships for Pi-ta and AVR-Pita using in vitro mutagenesis as well as analysis of naturally occurring variation for each gene. Virulent M. grisea field isolates world-wide either lack AVR- Pita homology or contain a class of closely related avr-pita alleles that fail to trigger Pi-ta-mediated resistance. Directed evolution of Pi-ta to recognize naturally occurring avr-pita alleles should lead to new genetic tools for control of rice blast disease. We will also discuss opportunities for using fungal population biology to guide R gene deployment, leading to an immediate impact on Pi-ta efficacy in the field.