Transient over-expression of barley BAX Inhibitor-1 weakens oxidative defence and MLA12-mediated resistance to Blumeria graminis f.sp. hordei |
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Authors: | RUTH EICHMANN,CORNELIA DECHERT,KARL-HEINZ KOGEL, RALPH HÜ CKELHOVEN |
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Affiliation: | Research Centre for BioSystems, Land Use and Nutrition, Institute of Phytopathology and Applied Zoology, Justus-Liebig-University Giessen, Heinrich-Buff Ring 26-32, D-35392 Giessen, Germany |
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Abstract: | BAX Inhibitor-1 (BI-1) is a conserved cell death suppressor protein. In barley, BI-1 ( HvBI-1 ) expression is induced upon powdery mildew infection and when over-expressed in epidermal cells of barley, HvBI-1 induces susceptibility to the biotrophic fungal pathogen Blumeria graminis . We co-expressed mammalian pro-apoptotic BAX together with HvBI-1, and the mammalian BAX antagonist BCL-XL in barley epidermal cells. BAX expression led to cessation of cytoplasmic streaming and collapse of the cytoplasm while co-expression of HvBI-1 and BCL-XL partially or completely, respectively, rescued cells from BAX lethality. When B. graminis was attacking epidermal cells, a green fluorescent protein fusion of HvBI-1 accumulated at the site of attempted penetration and was also present around haustoria. Over-expression of HvBI-1 in epidermal cells weakened a cell-wall-associated local hydrogen peroxide burst in a resistant mlo -mutant genotype and supported haustoria accommodation in race-specifically resistant MLA12 -barley. HvBI-1 is a cell death regulator protein of barley with the potential to suppress host defence reactions. |
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