Phytaspase, a relocalisable cell death promoting plant protease with caspase specificity

• Published in: The EMBO journal Vol. 29; no. 6; pp. 1149 - 1161
• Main Authors: Chichkova, Nina V, Shaw, Jane, Galiullina, Raisa A, Drury, Georgina E, Tuzhikov, Alexander I, Kim, Sang Hyon, Kalkum, Markus, Hong, Teresa B, Gorshkova, Elena N, Torrance, Lesley, Vartapetian, Andrey B, Taliansky, Michael
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 17.03.2010; Nature Publishing Group UK; Blackwell Publishing Ltd; Nature Publishing Group
• Subjects: abiotic stress; Apoptosis; Botany; caspases; Caspases - chemistry; Caspases - genetics; Caspases - metabolism; Cell Death; Cells, Cultured; EMBO07; Enzymes; Molecular biology; Mortality; Nicotiana - genetics; Nicotiana - metabolism; Oryza - genetics; Oryza - metabolism; Oryza sativa; Peptide Hydrolases - analysis; Peptide Hydrolases - genetics; Peptide Hydrolases - metabolism; Plant Proteins - chemistry; Plant Proteins - metabolism; Plants, Genetically Modified; programmed cell death; Proteases; Substrate Specificity; subtilisin-like proteases; Tobacco; Tobacco mosaic virus; subtilisin‐like proteases; tobacco mosaic virus; programmed cell death; caspases; abiotic stress
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/emboj.2010.1

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 asp artate‐specific prote ase ) 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.