During early differentiation starving Dictyostelium discoideum amoebae produce a burst of light that is enhanced by heat shock at the beginning of development. We report here pharmacological, genetic and spectral evidence that the chemiluminescence results from lipid peroxidation reactions following oxygen reduction by leakage of electrons from ubiquinone in mitochondrial electron transport, and perhaps by peroxisomal oxidation of urate. Our results are consistent with the view that heat shock causes oxidative stress, which in turn induces heat shock proteins and production of reduced oxygen metabolites.

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