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An Immunity-Triggering Effector from the Barley Smut Fungus Resides in an Ustilaginaceae-Specific Cluster Bearing Signs of Transposable Element-Assisted Evolution


Upon host infection, plant pathogens secrete suites of virulence effectors to suppress defense responses and support their own development. In certain cases, hosts evolve resistance genes that recognize such effectors or their actions to initiate defense responses. By deleting candidate genes, we identified the immune-triggering effector UhAvr1 from Ustilago hordei, a barley-infecting basidiomycete smut fungus. We show that this effector is expressed only when hyphae sense and infect barley coleoptile epidermal cells. Its presence in the fungus causes a necrotic reaction immediately upon penetration resulting in complete immunity in barley cultivars having resistance gene Ruh1. We show that fungal isolates that have mutated to change the expression of this non-crucial protein are avoiding recognition by the host, hence overcoming restriction by its immune response. In virulent isolates, transposable elements, known as genome modifiers, have separated the UhAvr1 coding region from its transcription signals. UhAvr1 is located in a larger cluster of ten effectors and is similar to clusters with more and further diversified effectors in the related maize pathogens U. maydis and Sporisorium reilianum. This study should lead us to discovering a mechanism by which this major cereal crop protects itself against this pathogen.


Vyšlo v časopise: An Immunity-Triggering Effector from the Barley Smut Fungus Resides in an Ustilaginaceae-Specific Cluster Bearing Signs of Transposable Element-Assisted Evolution. PLoS Pathog 10(7): e32767. doi:10.1371/journal.ppat.1004223
Kategorie: Research Article
prolekare.web.journal.doi_sk: https://doi.org/10.1371/journal.ppat.1004223

Souhrn

Upon host infection, plant pathogens secrete suites of virulence effectors to suppress defense responses and support their own development. In certain cases, hosts evolve resistance genes that recognize such effectors or their actions to initiate defense responses. By deleting candidate genes, we identified the immune-triggering effector UhAvr1 from Ustilago hordei, a barley-infecting basidiomycete smut fungus. We show that this effector is expressed only when hyphae sense and infect barley coleoptile epidermal cells. Its presence in the fungus causes a necrotic reaction immediately upon penetration resulting in complete immunity in barley cultivars having resistance gene Ruh1. We show that fungal isolates that have mutated to change the expression of this non-crucial protein are avoiding recognition by the host, hence overcoming restriction by its immune response. In virulent isolates, transposable elements, known as genome modifiers, have separated the UhAvr1 coding region from its transcription signals. UhAvr1 is located in a larger cluster of ten effectors and is similar to clusters with more and further diversified effectors in the related maize pathogens U. maydis and Sporisorium reilianum. This study should lead us to discovering a mechanism by which this major cereal crop protects itself against this pathogen.


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