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Arabidopsis plants perceive the phytohormones auxin and jasmonate (JA) through specific receptor proteins (Transport Inhibitor Response 1, TIR1, and Coronatine Insensitive 1, COI1, respectively), which are F-box-proteins and serve as components of ubiquitin-ligase complexes. The presence of the phytohormones leads to ubiquitinylation and proteasomal degradation of specific transcriptional repressors, thereby enabling auxin-dependent or JA-dependent gene expression. For TIR1 and auxin perception these repressors are AUX/IAA-proteins; for COI1 and JA-perception the corresponding repressors are the JAZ-proteins. A possible link of auxin- or JA-perception to signaling via inositol polyphosphates (IPPs) is presented by the notion that both TIR1 and COI1 contain IPPs as cofactors (TIR1: inositolhexakisphosphate, IP6; COI1: inositolpentakisphosphate, IP5) and we postulate that the IPPs in TIR1 and COI1 control receptor function. Because IP6 and IP5 can be interconverted by single-step enzymatic reactions, it appears plausible that the balance of these IPP-cofactors is crucial for the orchestration of auxin-dependent vs. JA-dependent processes in plants. The proposed experiments are designed to first characterize the so-far-unknown dynamics of IP5 and IP6 upon gravistimulation and wounding. Data acquired in the planned project will elucidate the still-enigmatic roles of IPPs in plants and contribute to the understanding how the outputs of different signaling pathways are integrated.