Hydrogen peroxide and expression of hipI-superoxide dismutase are associated with the development of secondary cell walls in Zinnia elegans
2005
Karlsson, Marlene | Melzer, Michael | Prokhorenko, Isabella | Johansson, Thorsten | Wingsle, Gunnar
A special form of a CuZn-superoxide dismutase with a high isoelectric point (hipI-SOD; EC 1.15.1.1) and hydrogen peroxide (H₂O₂) production were studied during the secondary cell wall formation of the inducible tracheary element cell-culture system of Zinnia elegans L. Confocal microscopy after labelling with 2',7'-dichlorofluorescin diacetate showed H₂O₂ to be located largely in the secondary cell walls in developing tracheary elements. Fluorescence-activated cell sorting analysis showed there were lower levels of H₂O₂ in the population containing tracheary elements when H₂O₂ scavengers such as ascorbate, catalase, and reduced glutathione were applied to the cell culture. Inhibitors of NADPH oxidase and SOD also reduced the amount of H₂O₂ in the tracheary elements. Furthermore, addition of these compounds to cell cultures at the time of tracheary element initiation reduced the amount of lignin and the development of the secondary cell walls. Analysis of UV excitation under a confocal laser scanning microscope confirmed these results. The expression of hipI-SOD increased as the number of tracheary elements in the cell culture increased and developed. Additionally, immunolocalization of a hipI-SOD isoform during the tracheary element differentiation showed a developmental build-up of the protein in the Golgi apparatus and the secondary cell wall. These findings suggest a novel hipI-SOD could be involved in the regulation of H₂O₂ required for the development of the secondary cell walls of tracheary elements.
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