title: Post mortem function of AtMC9 in xylem vessel elements.
abstract: Cell death of xylem elements is manifested by rupture of the tonoplast and subsequent autolysis of the cellular contents. Metacaspases have been implicated in various forms of plant cell death but regulation and execution of xylem cell death by metacaspases remains unknown. Analysis of the type II metacaspase gene family in Arabidopsis thaliana supported the function of METACASPASE 9 (AtMC9) in xylem cell death. Progression of xylem cell death was analysed in protoxylem vessel elements of 3-d-old atmc9 mutant roots using reporter gene analysis and electron microscopy. Protoxylem cell death was normally initiated in atmc9 mutant lines, but detailed electron microscopic analyses revealed a role for AtMC9 in clearance of the cell contents post mortem, that is after tonoplast rupture. Subcellular localization of fluorescent AtMC9 reporter fusions supported a post mortem role for AtMC9. Further, probe-based activity profiling suggested a function of AtMC9 on activities of papain-like cysteine proteases. Our data demonstrate that the function of AtMC9 in xylem cell death is to degrade vessel cell contents after vacuolar rupture. We further provide evidence on a proteolytic cascade in post mortem autolysis of xylem vessel elements and suggest that AtMC9 is part of this cascade.
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 90187, Umeå, Sweden.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bollhöner
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 90187, Umeå, Sweden.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.
authors.forename: Simon
authors.initials: S
authors.lastname: Stael
authors.affiliation: UPS, UMR 5546, Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, Castanet-Tolosan, France.|Centre National de la Recherche Scientifique, CNRS, UMR 5546, Laboratoire de Recherche en Sciences Végétales, Castanet-Tolosan, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Denancé
authors.affiliation: Plant Biology, Department of Biosciences, University of Helsinki, 00014, Helsinki, Finland.
authors.forename: Kirk
authors.initials: K
authors.lastname: Overmyer
authors.affiliation: UPS, UMR 5546, Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, Castanet-Tolosan, France.|Centre National de la Recherche Scientifique, CNRS, UMR 5546, Laboratoire de Recherche en Sciences Végétales, Castanet-Tolosan, France.
authors.forename: Deborah
authors.initials: D
authors.lastname: Goffner
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Van Breusegem
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 90187, Umeå, Sweden.
authors.forename: Hannele
authors.initials: H
authors.lastname: Tuominen
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D059748:Proteolysis; D044224:Pseudomonas syringae / Q000472:pathogenicity; D011993:Recombinant Fusion Proteins; D014617:Vacuoles / Q000378:metabolism; D052584:Xylem / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; D011993:Recombinant Fusion Proteins; D020169:Caspases; C516211:metacaspase 9, Arabidopsis
keywords: Arabidopsis thaliana; autolysis; metacaspase; protease; vessel element; xylem cell death