The presence and subcellular localization of caspase 3-like proteinases inplant cells

Caspases play a very important role in initiating and executing apoptotic p rocesses in animal cells. In this study we show that plant mitochondria wer e able to initiate the activation of caspase 3 in a Xenopus cell free syste m. Caspase 3-like activity was found to be present in plant cells and could only be inhibited by the specific caspase 3 inhibitor N-acetyl-Asp-Glu-Val -Asp-fluoromethylketone (Ac-DEVD-fmk) and not by cysteine protease inhibito rs. By micro-injection of the caspase 3 substrate in living Chara cells we showed that caspase 3-like activity was mainly present in the cytosol rathe r than in the vacuole. This is the first time that in vivo caspase 3-like a ctivity has been demonstrated in plants. (C) 2000 Federation of European Bi ochemical Societies. Published by Elsevier Science B.V. All rights reserved .