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Post mortem function of A t MC 9 in xylem vessel elements
Author(s) -
Bollhöner Benjamin,
Zhang Bo,
Stael Simon,
Denancé Nicolas,
Overmyer Kirk,
Goffner Deborah,
Van Breusegem Frank,
Tuominen Hannele
Publication year - 2013
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12387
Subject(s) - xylem , autolysis (biology) , programmed cell death , vacuole , microbiology and biotechnology , biology , mutant , chemistry , biochemistry , botany , apoptosis , enzyme , gene , cytoplasm
Summary 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 A rabidopsis thaliana supported the function of METACASPASE 9 ( A t MC 9 ) 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 A t MC 9 in clearance of the cell contents post mortem , that is after tonoplast rupture. Subcellular localization of fluorescent A t MC 9 reporter fusions supported a post mortem role for A t MC 9. Further, probe‐based activity profiling suggested a function of A t MC 9 on activities of papain‐like cysteine proteases. Our data demonstrate that the function of A t MC 9 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 A t MC 9 is part of this cascade.