Figure 8.

A working model for the impact of Pep-PEPR-signaling on starvation-induced senescence. Continuous darkness leads to starvation due to energy deprivation and lack of nutrients. In order to survive nutrients are remobilized e.g., by induction of autophagy. During short periods of starvation this response supports tissue survival (1) whereas continuous starvation and autophagy (2) eventually leads to senescence. In our study we found that darkness/starvation induces PROPEP3 transcription. We hypothesize that this might also promote the release of mature Pep3, which activates PEPR signaling to fine tune nutrient remobilization of responsive cells via chlorophyll breakdown and autophagy. In case of the leaf discs or detached mature leaves, supplementation of the assay solution with Peps triggers a detrimental turnover of cellular components, thus shortens the time of survival and accelerates the onset of senescence during continuous darkness.