title: The mitochondrial outer membrane AAA ATPase AtOM66 affects cell death and pathogen resistance in Arabidopsis thaliana.
abstract: One of the most stress-responsive genes encoding a mitochondrial protein in Arabidopsis (At3g50930) has been annotated as AtBCS1 (cytochrome bc1 synthase 1), but was previously functionally uncharacterised. Here, we show that the protein encoded by At3g50930 is present as a homo-multimeric protein complex on the outer mitochondrial membrane and lacks the BCS1 domain present in yeast and mammalian BCS1 proteins, with the sequence similarity restricted to the AAA ATPase domain. Thus we propose to re-annotate this protein as AtOM66 (Outer Mitochondrial membrane protein of 66 kDa). While transgenic plants with reduced AtOM66 expression appear to be phenotypically normal, AtOM66 over-expression lines have a distinct phenotype, showing strong leaf curling and reduced starch content. Analysis of mitochondrial protein content demonstrated no detectable changes in mitochondrial respiratory complex protein abundance. Consistent with the stress inducible expression pattern, over-expression lines of AtOM66 are more tolerant to drought stress but undergo stress-induced senescence earlier than wild type. Genome-wide expression analysis revealed a constitutive induction of salicylic acid-related (SA) pathogen defence and cell death genes in over-expression lines. Conversely, expression of SA marker gene PR-1 was reduced in atom66 plants, while jasmonic acid response genes PDF1.2 and VSP2 have increased transcript abundance. In agreement with the expression profile, AtOM66 over-expression plants show increased SA content, accelerated cell death rates and are more tolerant to the biotrophic pathogen Pseudomonas syringae, but more susceptible to the necrotrophic fungus Botrytis cinerea. In conclusion, our results demonstrate a role for AtOM66 in cell death and amplifying SA signalling.
authors.affiliation: ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Bayliss Building M316, 35 Stirling Highway, Crawley, WA, 6009, Australia; Department of Botany, ARC Centre of Excellence in Plant Energy Biology, School of Life Science, La Trobe University, Bundoora, Vic., 3086, Australia.
authors.forename: Botao
authors.initials: B
authors.lastname: Zhang
authors.forename: Olivier
authors.initials: O
authors.lastname: Van Aken
authors.forename: Louise
authors.initials: L
authors.lastname: Thatcher
authors.forename: Inge
authors.initials: I
authors.lastname: De Clercq
authors.forename: Owen
authors.initials: O
authors.lastname: Duncan
authors.forename: Simon R
authors.initials: SR
authors.lastname: Law
authors.forename: Monika W
authors.initials: MW
authors.lastname: Murcha
authors.forename: Margaretha
authors.initials: M
authors.lastname: van der Merwe
authors.forename: Hamed Soren
authors.initials: HS
authors.lastname: Seifi
authors.forename: Chris
authors.initials: C
authors.lastname: Carrie
authors.forename: Christopher
authors.initials: C
authors.lastname: Cazzonelli
authors.forename: Jordan
authors.initials: J
authors.lastname: Radomiljac
authors.forename: Monica
authors.initials: M
authors.lastname: Höfte
authors.forename: Karam B
authors.initials: KB
authors.lastname: Singh
authors.forename: Frank
authors.initials: F
authors.lastname: Van Breusegem
authors.forename: James
authors.initials: J
authors.lastname: Whelan
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000382:microbiology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020171:Botrytis / Q000472:pathogenicity; D016923:Cell Death / Q000235:genetics; D003517:Cyclopentanes / Q000378:metabolism; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D051336:Mitochondrial Membranes / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D054883:Oxylipins / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics; D030821:Plants, Genetically Modified; D044224:Pseudomonas syringae / Q000472:pathogenicity; D020156:Salicylic Acid / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; C000607130:OM66 protein, Arabidopsis; D054883:Oxylipins; C011006:jasmonic acid; D020156:Salicylic Acid
keywords: ATPase; Arabidopsis; cell death; mitochondria; pathogen defence; stress