Engineering CC-HMA-NLR immune receptors for disease resistance in crops (ERiC)

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Engineering the plant immune system provides opportunities to develop novel genetic approaches to disease resistance in key crops that feed the world. In previous work, we determined the molecular details of how integrated HMA domains in the rice paired NLRs Pik-1/Pik-2 recognise different alleles of the rice blast pathogen effector AVR-Pik. This work demonstrated the potential of conferring enhanced resistance to plant diseases by engineering increased binding strength between NLR-IDs and pathogen effectors. This proof-of-principle study has paved the way for the work proposed here, to generate chimeric CC-HMA-NLRs with bespoke domains that detect divergent, widely distributed effectors from across host-specific pathogen lineages. This is important as different M. oryzae lineages infect different cereal crops. The research performed here will inform approaches to address epidemics of diseases such as wheat blast, which has recently emerged in Asia and Africa.

To deliver our objectives we propose a multi-disciplinary approach combining biochemistry, structural biology, genetics and plant pathology. Building on our preliminary data, we will first determine the extent to which cereal HMA proteins bind variants of the M. oryzae PWL effector family to understand specificity and identify targets for CC-HMA-NLR engineering. We will then use in vitro and in planta assays to optimise the binding of these HMA domains to PWL effectors, including incorporating into the CC-HMA-NLR scaffold (the latter will also allow monitoring of immune responses). Further, we will develop the Pik-1/Pik-2 system outside the HMA domain to deliver optimal immune responses. Finally, we will transform rice, barley and wheat cultivars with engineered CC-HMA-NLRs and test for resistance against both Lab strains of M. oryzae with different PWL effector complements and natural isolates collected from disease outbreaks.