Structure, function and evolution of plant disease resistance genes.

Area of Science:

• Plant pathology
• Molecular genetics
• Genomics

Background:

• Gene-for-gene plant disease resistance involves pathogen perception and response.
• Specific receptors encoded by resistance (R) genes recognize pathogen strains.
• Plants possess diverse R genes with varied specificities.

Purpose of the Study:

• To investigate the generation and maintenance of R-gene diversity.
• To understand the role of leucine-rich repeats (LRR) in R-gene specificity.
• To explore potential for non-specific resistance.

Main Methods:

• Analysis of R-gene polymorphism generation (gene duplication, mutation, recombination).
• Examination of Arabidopsis thaliana genome sequence data.
• Mutation experiments to dissociate R-gene signaling from specificity.

Main Results:

• R-gene polymorphism arises from duplication, point mutation, and repeat alteration.
• Recombination further diversifies R-gene sequences.
• Nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes constitute ~1% of the Arabidopsis genome, with LRR determining specificity.

Conclusions:

• Pathogen pressure drives selection for functional resistance specificities, maintaining R-gene diversity.
• Mutation experiments suggest potential for engineered non-specific resistance in plants.