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Abstract:
The arms race between hosts and pathogens can drive rapid co-evolution of immune receptors and the pathogen effectors. In Arabidopsis thaliana, certain alleles of the NLR encoding RPP1 locus detect variants of the Hyaloperonospora arabidopsidis effector ATR1 by direct interaction. RPP1 appears in multiple copies in A. thaliana genomes, and both copy number and protein sequence differ greatly among natural accessions. To better understand RPP1/ATR1 coevolution, we are testing a combinatorial interaction matrix of diverse natural isolates of both the host and the pathogen protein. RPP1 allelic diversity has been deduced from long-read genome assemblies of multiple A. thaliana accessions. ATR1 diversity has been described from a collection of over one hundred new H. arabidopsidis isolates from most of the European range of A. thaliana. We discovered 25 alleles at the ATR1 locus and are using both heterologous expression of ATR1 variants in bacteria in combination with A. thaliana infection, and heterologous co-expression of RPP1 and ATR1 variants in N. benthamiana, to determine specificities on host and pathogen side. The impact of the RPP1/ATR1 coevolution in this pathosystem may lead to a deeper understanding of its role in the oomycete pathogenicity and the function of the multi-allelic RPP1 locus on the host side.
