Publications by authors named "C Sybesma"

Two varieties of tobacco (Nicotiana tabacum var PBD6 and var SR1) were used to generate transgenic lines overexpressing Mn-superoxide dismutase (MnSOD) in the chloroplasts. The overexpressed MnSOD suppresses the activity of those SODs (endogenous MnSOD and chloroplastic and cytosolic Cu/ZnSOD) that are prominent in young leaves but disappear largely or completely during aging of the leaves. The transgenic and control plants were grown at different light intensities and were then assayed for oxygen radical stress tolerance in leaf disc assays and for abundance of antioxidant enzymes and substrates in leaves.

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In plants, environmental adversity often leads to the formation of highly reactive oxygen radicals. Since resistance to such conditions may be correlated with the activity of enzymes involved in oxygen detoxification, we have generated transgenic tobacco plants which express elevated levels of manganese superoxide dismutase (MnSOD) within their chloroplasts or mitochondria. Leaf discs of these plants have been analyzed in conditions in which oxidative stress was generated preferentially within one or the other organelle.

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The induction of anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica by sulfide was shown to involve the synthesis of a "sulfide oxidizing factor"; this factor, partly adsorbed on the thylakoid membrane, can be recovered in the soluble phase and is active also on membranes from oxygenically grown cells. The factor is required for sulfide dependent light-induced hydrogen evolution. It accelerates electron transport from sulfide to the electron donor of photosystem I, P700, in membranes from cells in which anoxygenic photosynthesis is induced.

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