The role of hydrogen peroxide as signalling molecule in leaf senescence and its impact on senescence-induced nitrogen mobilisation

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Despite the importance of senescence, our knowledge on the regulatory mechanisms of this process is still fragmentary. For the model plant Arabidopsis thaliana we have previously shown that during the onset of leaf senescence the hydrogen peroxide concentration in the leaf cells increases by a complex regulatory interplay of the hydrogen peroxide scavenging enzymes. This hydrogen peroxide peak is involved in the onset of senescence most likely by transcriptional up-regulation of important senescence-associated transcription factors like WRKY53 or NAC92. In oilseed rape, hydrogen peroxide is also up-regulated during developmental senescence. In this approach, we will analyze the role of hydrogen peroxide in the expression of genes involved in the mobilization of nitrogenous compounds in more detail in the crop plant oilseed rape. Here, we will focus on the expression of seed storage protein genes which were unexpectedly expressed in leaves following the hydrogen peroxide profiles and possibly serving as a putative interim N storage. This was detected only in oilseed rape but not in Arabidopsis. In addition, we have several lines of evidence that the cellular compartment where the hydrogen peroxide is formed is important for its signalling function. Therefore, we would like to proceed with the establishment of an in vivo imaging system for hydrogen peroxide using a hydrogen peroxide sensitive GFP directed to different cellular compartments in Arabidopsis and oilseed rape to understand its regulatory role more precisely and in the long run create plants which can be very specifically manipulated in senescence regulation and nitrogen mobilization.Keywords: Hydrogen peroxide as signalling molecule, hydrogen peroxide scavenging enzymes (catalase and ascorbate peroxidase), role of hydrogen peroxide in gene expression of SAGs, in vivo hydrogen peroxide imaging system.