Phototoxicity and Programmed Cell Death

The production of ROS by phototoxicity mechanisms links programmed cell death to photosensitization phenomena. Chlorophyll-sensitized production of xO2 occurs during senescence (Biswal, 1995), and ROS are important signals in the hypersensitive response (Pontier et al., 1998), but literature on phototoxicity as a mediator of apoptosis in plants is scarce. Phototoxic poisoning of flax cotyledons by rose bengal speeds up the symptoms of senescence (Percival and Dodge, 1983). Interestingly, photodynamic therapy of human cancers is thought to function via an apoptotic route rather than by a direct photokilling of the cancer cells by the phototoxicity reaction (Dougherty et al., 1998).

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