Inositol pyrophosphates (PP-InsPs) are emerging as key signalling molecules involved in diverse cellular processes in eukaryotes. In plants, these molecules regulate critical pathways, including phosphate homeostasis, auxin and jasmonate signalling, and other metabolic and developmental responses. Despite their significance, the full scope of PP-InsP interactions and their molecular mechanisms remain largely unexplored. This thesis aims to deepen our understanding of PP-InsP function in Arabidopsis thaliana by identifying novel PP-InsP interacting proteins and elucidating their roles in cellular signalling networks. An affinity-based interaction screen was performed using biotinylated derivatives of InsP6, 5 InsP7, and 1,5-InsP8 to capture PP-InsP-binding proteins from Arabidopsis protein extracts. Mass spectrometry analysis identified nearly 600 putative interactors. The identified proteins are located in multiple cellular pathways, including ribosome biogenesis, RNA processing, endocytosis, and signal transduction. Among the identified interactors, two highly conserved kinase families, CASEIN KINASE 1 (CK1) and CASEIN KINASE 2 (CK2), emerged as strong candidates for PP-InsP regulation. Biochemical assays and structural analyses confirmed PP-InsP binding to these kinases, and in vitro phosphorylation studies demonstrated that PP-InsP modulates their enzymatic activity. The data suggests that PP-InsP may function as a cofactor or allosteric regulator, influencing kinase-substrate interactions and downstream signalling pathways. These findings provide new insights into PP-InsP-mediated regulation in plants, particularly in protein phosphorylation and signal transduction. By characterizing novel PP-InsP interactors and their biochemical functions, this thesis expands our understanding of plant signalling networks. The interaction screen presents a valuable tool for future research on PP-InsP dependent regulation in eukaryotic systems.