Evidence for the involvement of cysteine proteases in the regulation of methyl jasmonate-induced cell death in grapevine
A new system to study programmed cell death (PCD) in plants is described. Grapevine ( Vitis vinifera L., cv. Limberger) leaves and suspension cells were induced to undergo a form of cell death that mimics the hypersensitive response (HR) by treatment with a lipid-derived molecule, methyl jasmonate (MeJA). This chemical-induced cell death was accompanied by the characteristic features of apoptosis in animal and plant cells, such as typical changes in nuclear morphology, the fragmentation of the nucleus and protoplast collapse. Local and ectopic treatment of grapevine leaves with phenylmethylsulfonyl fluoride (PMSF), leupeptin, and especially with a specific inhibitor of cysteine proteases, E-64, inhibited MeJA-induced cysteine protease activity and blocked PCD triggered by 50 muM MeJA. These results indicate that proteolysis plays a crucial role in MeJA-induced apoptosis and that this type of PCD can be regulated by activity poised between the cysteine protease and the cysteine protease inhibitor.