Diversity at the barley Mla powdery mildew resistance locus and its cognate pathogen effectors
|演題||Diversity at the barley Mla powdery mildew resistance locus and its cognate pathogen effectors|
|講演者||Dr. Takaki Maekawa (Max Planck Institute for Plant Breeding Research)|
Gene-for-gene immunity is frequently found in interactions between plants and host-adapted pathogens and reflects population-level diversification of immune receptors detecting matching pathogen effectors. Barley mildew resistance locus a (Mla) has been subject to extensive functional diversification, resulting in allelic resistance specificities each recognizing a cognate AVRa gene of the powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh). De novo transcript assembly of a set of defined 50 wild-barley (Hordeum spontaneum) accessions revealed a rich sequence diversity of Mla resistance locus, which is not linked to geographic isolation/ population structure, providing evidence for balancing selection at the Mla locus in wild barley population. To better understand the diversification of the Mla resistance locus , we applied a transcriptome-wide association study among 27 Bgh isolates containing different AVRa genes and identified AVRa1, AVRa9, AVRa10, AVRa13 and AVRa22, encoding small secreted proteins recognized by Mla1, Mla9, Mla10, Mla13and Mla22 alleles, respectively. Yeast two-hybrid assay and split-luciferase assay suggest that effector recognition specificity is mediated by a direct AVRA-MLA interaction, which could explain the conserved effector recognition by the receptors in distantly related Arabidopsis thaliana and Nicotiana benthamiana plants. Reconstitution of the barley MLA-triggered immunity in A. thaliana has enabled us to learn the evolutionarily conserved defense mechanism of the major class of intracellular immune receptor designated NLR (nucleotide-binding domain leucine-rich repeat) family. In this seminar, signal initiation mechanism by plant NLR family will also be discussed.
References: Jacob et al., (2017) New Phytol 217(4):1667-1680. Lu et al., (2016) PNAS 113(42): E6486-E6495.
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