An effector-detector domain in a rice immune receptor: towards structure-guided design of new disease resistance proteins

Lead Research Organisation: John Innes Centre
Department Name: Contracts Office

Abstract

The aims of this proposal are to define the molecular mechanisms underlying recognition of a rice blast effector protein family (AVR-Pik) by an unconventional domain incorporated into rice resistance proteins (Pik-HMAs) during evolution. Arms-race co-evolution, developed through direct protein-protein interaction, has resulted in an allelic series of AVR-Pik effectors and Pik resistance proteins that show deferential recognition patterns. This affects the capability of rice cultivars to respond to infection. Understanding the structural basis of recognition between these effectors and plant resistance proteins presents opportunities to engineer novel disease resistance specificities in rice, and perhaps other plant species.

To deliver on our objectives, we propose a novel multi-disciplinary approach combining biochemistry, structural biology and plant biology, with the latter directly in the host pathosystem. Building on our preliminary data, which includes the first example of a structure of a plant pathogen effector bound to a plant intracellular immune receptor, we will interrogate the interactions between AVR-Pik effectors and Pik resistance protein domains in vitro and in planta. This will include both mutational analysis based on our structural work and also natural variants of AVR-Pik and Pik-HMA domains. Further, we have identified proteins called s-HMAs as putative susceptibility factors targeted by AVR-Pik effectors. Fascinatingly, these s-HMAs are sequence (and presumably structurally)-related to the resistance protein HMA domains. We will also characterise the interaction and activity of AVR-Pik effectors with these s-HMAs. Finally, we will use structure-guided mutagenesis to engineer Pik resistance proteins with novel, extended recognition specificities (to include as-yet unrecognised AVR-Pik alleles) and also transfer HMA-mediated recognition to NLRs of other plants.

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