Editors' ChoiceApoptosis

From Mammals to Yeast to Plants

Science's STKE  26 Sep 2000:
Vol. 2000, Issue 51, pp. tw5
DOI: 10.1126/stke.2000.51.tw5

Apoptosis (programmed cell death) occurs in many multicellular organisms, including plants where it is involved in limiting the spread of invading pathogens by a process called the hypersensitive response. The plant response to pathogens also involves an oxidative burst that produces reactive oxygen species. Expression of proapoptotic proteins from mammals in yeast causes cell death. Kampranis et al. designed a strategy based on the yeast two hybrid system and yeast sensitivity to the expression of mammalian Bax to characterize plant genes involved in opposing Bax-induced apoptosis through direct and indirect mechanisms. The screen yielded several clones related to antioxidant proteins. The clone that was most effective at inhibiting cell death caused by reactive oxygen species and caused by Bax expression was then cloned from tomato. The protein sequence suggested that the clone encoded a glutathione S-transferase (GST), and expression and isolation of the protein from bacteria confirmed this enzymatic activity, as well as glutathione peroxidase (GPX) activity. Expression of this GST/GPX protein in yeast expressing Bax blocked Bax-induced inhibition of the cell cycle, restored glutathione levels to wild type, and inhibited dissipation of the mitochondrial membrane potential. Thus, this unusual cross-kingdom approach may point to novel genes involved in the plant defense pathway, as well as provide more evidence for the role of oxidative stress in Bax-mediated cell death.

Kampranis, S.C., Damianova, R., Atallah, M., Toby, G., Kondi, G., Tsichlis, P.N., and Makris, A.M. (2000) A novel plant glutathione S-transferase/peroxidase suppresses Bax lethality in yeast. J. Biol. Chem. 275: 29207-29216. [Abstract] [Full Text]