Oxidative stress could be responsible for the recalcitrance of plant protoplasts

Expression of totipotency and regeneration potentiality of plant protoplasts is a complex developmental phenomenon. The isolation per se is a stress-inducing procedure, during which, among others, active oxygen species (AOS) are generated. Thereafter, protoplasts undergo cell wall reconstitution, cell elongation and re-enter the cell cycle. AOS are known to participate in cell wall cross-linking and recently hydroxyl radicals were proposed to participate in cell wall loosening. On the other hand, if the antioxidant genes and the overall AOS scavenging machinery is not induced, protoplasts may suffer from oxidative stress and peroxidation of membrane lipids. In an effort to identify potential factors contributing to recalcitrance of plant protoplasts, we present the available information, which correlates AOS and oxidative stress with cell wall reconstitution, dedifferentiation, cell cycle progression, and cell death. Reduced antioxidant machinery and altered redox homeostasis seem to affect the regenerating potential of plant protoplasts and inevitably the protoplast fate (re-entry into cell cycle or cell death).