Phytaspase, a relocalisable cell death promoting plant protease with caspase specificity.
Caspases are cysteine-dependent proteases and are important components of animal apoptosis. They introduce specific breaks after aspartate residues in a number of cellular proteins mediating programmed cell death (PCD). Plants encode only distant homologues of caspases, the metacaspases that are involved in PCD, but do not possess caspase-specific proteolytic activity. Nevertheless, plants do display caspase-like activities indicating that enzymes structurally distinct from classical caspases may operate as caspase-like proteases. Here, we report the identification and characterisation of a novel PCD-related subtilisin-like protease from tobacco and rice named phytaspase (plant aspartate-specific protease) that possesses caspase specificity distinct from that of other known caspase-like proteases. We provide evidence that phytaspase is synthesised as a proenzyme, which is autocatalytically processed to generate the mature enzyme. Overexpression and silencing of the phytaspase gene showed that phytaspase is essential for PCD-related responses to tobacco mosaic virus and abiotic stresses. Phytaspase is constitutively secreted into the apoplast before PCD, but unexpectedly is re-imported into the cell during PCD providing insights into how phytaspase operates.
Chichkova
Nina V
NV
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia.
Shaw
Jane
J
Galiullina
Raisa A
RA
Drury
Georgina E
GE
Tuzhikov
Alexander I
AI
Kim
Sang Hyon
SH
Kalkum
Markus
M
Hong
Teresa B
TB
Gorshkova
Elena N
EN
Torrance
Lesley
L
Vartapetian
Andrey B
AB
Taliansky
Michael
M
D020169:Caspases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D002478:Cells, Cultured; D012275:Oryza / Q000235:genetics / Q000378:metabolism; D010447:Peptide Hydrolases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D013379:Substrate Specificity; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
D010940:Plant Proteins; D010447:Peptide Hydrolases; D020169:Caspases