Abstract:

In order to analyze the signaling function of hydrogen peroxide (H₂O₂) production in senescence in more detail, we manipulated intracellular H₂O₂ levels in Arabidopsis thaliala (L.) Heynh by using the hydrogen-peroxide-sensitive part of the Escherichia coli transcription regulator OxyR, which was directed to the cytoplasm as well as into the peroxisomes. H₂O₂ levels were lowered and senescence was delayed in both transgenic lines, but OxyR was found to be more effective in the cytoplasm. To transfer this knowledge to crop plants, we analyzed oilseed rape plants Brassica napus L. cv. Mozart for H₂O₂ and its scavenging enzymes catalase (CAT) and ascorbate peroxidase (APX) during leaf and plant development. H₂O₂ levels were found to increase during bolting and flowering time, but no increase could be observed in the very late stages of senescence. With increasing H₂O₂ levels, CAT and APX activities declined, so it is likely that similar mechanisms are used in oilseed rape and Arabidopsis to control H₂O₂ levels. Under elevated CO₂ conditions, oilseed rape senescence was accelerated and coincided with an earlier increase in H₂O₂ levels, indicating that H₂O₂ may be one of the signals to inducing senescence in a broader range of Brassicaceae.

Key words: Arabidopsis thaliana, Brassica napus, E. coli Oxy-RD, intracellular hydrogen peroxide, senescence phenotype, catalase, ascorbate Peroxidase, elevated CO₂