title: Transient over-expression of barley BAX Inhibitor-1 weakens oxidative defence and MLA12-mediated resistance to Blumeria graminis f.sp. hordei.
abstract: SUMMARY 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-X(L) 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-X(L) 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.
authors.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.
authors.forename: Ruth
authors.initials: R
authors.lastname: Eichmann
authors.forename: Cornelia
authors.initials: C
authors.lastname: Dechert
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Kogel
authors.forename: Ralph
authors.initials: R
authors.lastname: Hückelhoven