title: The BRI1-associated kinase 1, BAK1, has a brassinolide-independent role in plant cell-death control.
abstract: Programmed cell death (PCD) is a common host response to microbial infection [1-3]. In plants, PCD is associated with immunity to biotrophic pathogens, but it can also promote disease upon infection by necrotrophic pathogens [4]. Therefore, plant cell-suicide programs must be strictly controlled. Here we demonstrate that the Arabidopsis thaliana Brassinosteroid Insensitive 1 (BRI1)-associated receptor Kinase 1 (BAK1), which operates as a coreceptor of BRI1 in brassinolide (BL)-dependent plant development, also regulates the containment of microbial infection-induced cell death. BAK1-deficient plants develop spreading necrosis upon infection. This is accompanied by production of reactive oxygen intermediates and results in enhanced susceptibility to necrotrophic fungal pathogens. The exogenous application of BL rescues growth defects of bak1 mutants but fails to restore immunity to fungal infection. Moreover, BL-insensitive and -deficient mutants do not exhibit spreading necrosis or enhanced susceptibility to fungal infections. Together, these findings suggest that plant steroid-hormone signaling is dispensable for the containment of infection-induced PCD. We propose a novel, BL-independent function of BAK1 in plant cell-death control that is distinct from its BL-dependent role in plant development.
authors.affiliation: Department of Plant Biochemistry, Center for Plant Molecular Biology, Eberhard-Karls-University Tübingen, Tübingen, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Kemmerling
authors.forename: Anne
authors.initials: A
authors.lastname: Schwedt
authors.forename: Patricia
authors.initials: P
authors.lastname: Rodriguez
authors.forename: Sara
authors.initials: S
authors.lastname: Mazzotta
authors.forename: Markus
authors.initials: M
authors.lastname: Frank
authors.forename: Synan Abu
authors.initials: SA
authors.lastname: Qamar
authors.forename: Tesfaye
authors.initials: T
authors.lastname: Mengiste
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Betsuyaku
authors.forename: Jane E
authors.initials: JE
authors.lastname: Parker
authors.forename: Carsten
authors.initials: C
authors.lastname: Müssig
authors.forename: Bart P H J
authors.initials: BP
authors.lastname: Thomma
authors.forename: Catherine
authors.initials: C
authors.lastname: Albrecht
authors.forename: Sacco C
authors.initials: SC
authors.lastname: de Vries
authors.forename: Heribert
authors.initials: H
authors.lastname: Hirt
authors.forename: Thorsten
authors.initials: T
authors.lastname: Nürnberger
mesh_terms: D017360:Arabidopsis / Q000276:immunology* / Q000382:microbiology / Q000502:physiology; D029681:Arabidopsis Proteins / Q000502:physiology*; D060406:Brassinosteroids; D016923:Cell Death / Q000502:physiology; D002777:Cholestanols / Q000378:metabolism; D020869:Gene Expression Profiling; D010935:Plant Diseases; D010937:Plant Growth Regulators / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D044224:Pseudomonas syringae / Q000276:immunology* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013260:Steroids, Heterocyclic / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D002777:Cholestanols; D010937:Plant Growth Regulators; D013260:Steroids, Heterocyclic; C463660:BAK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; C023623:brassinolide