Induction of cell death in Arabidopsis by superoxide in combination with salicylic acid or with protein synthesis inhibitors

Induction of programmed cell death (PCD) by oxidative stress is a widesprea d phenomenon in all living organisms. The degree of cell death depends on t he concentration of oxidants and on environmental and physiological conditi ons. in plants, generation of reactive oxygen intermediates (ROI) occurs du ring many biotic and abiotic stresses. Recently, a number of spontaneous ce ll death mutants have been isolated in Arabidopsis. In one of the mutants ( lsd1) induction of PCD has been attributed to superoxide (O-2(.-)). Here we show that while in wild type plants generation of superoxide is symptomles s, combination of O-2(.-) with salicylic acid or with inhibitors of protein synthesis induced PCD. Cell death induced by these treatments was suppress ed by protease inhibitors, indicating an active response. PCD induced by bo th treatments was preceded by nuclear condensation, which is a hallmark of apoptosis in plants and animals. These results may explain increased sensit ivity to oxidative stress under certain physiological conditions, associate d with high levels of salicylic acid or decrease in protein synthesis. (C) 2000 Elsevier Science Inc.