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The Involvement of Cysteine Proteases and Protease Inhibitor Genes in the Regulation of Programmed Cell Death in Plants
Mazal Solomon, Beatrice Belenghi, Massimo Delledonne, Ester Menachem and Alex Levine
The Plant Cell
Vol. 11, No. 3 (Mar., 1999), pp. 431-443
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/3870871
Page Count: 13
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Programmed cell death (PCD) is a process by which cells in many organisms die. The basic morphological and biochemical features of PCD are conserved between the animal and plant kingdoms. Cysteine proteases have emerged as key enzymes in the regulation of animal PCD. Here, we show that in soybean cells, PCD-activating oxidative stress induced a set of cysteine proteases. The activation of one or more of the cysteine proteases was instrumental in the PCD of soybean cells. Inhibition of the cysteine proteases by ectopic expression of cystatin, an endogenous cysteine protease inhibitor gene, inhibited induced cysteine protease activity and blocked PCD triggered either by an avirulent strain of Pseudomonas syringae pv glycinea or directly by oxidative stress. Similar expression of serine protease inhibitors was ineffective. A glutathione S-transferase-cystatin fusion protein was used to purify and characterize the induced proteases. Taken together, our results suggest that plant PCD can be regulated by activity poised between the cysteine proteases and the cysteine protease inhibitors. We also propose a new role for proteinase inhibitor genes as modulators of PCD in plants.
The Plant Cell © 1999 American Society of Plant Biologists (ASPB)