Osmotic stress-induced phosphoinositide and inositol phosphate signalling in plants

Polyphosphoinositides (PPIs) became famous for their role in inositol-1,4,5-trisphosphate (InsP(3)) mediated-Ca2+ signalling in mammalian cells, generated through signal-activated phospholipase C (PLC) hydrolysis of the minor membrane lipid, phosphatidylinositol-4,5-bisphosphate. For many years, the plant field followed the same paradigm, however, slowly a completely different picture is emerging. Moreover, various novel PPI-signalling compounds have been identified meanwhile, with new functions and targets coming to light. These include lipids phosphorylated at the D3-position of inositol but also water-soluble inositolpolyphosphates (IPPs). For several of them, a relationship to water stress has been reported. This review summarizes the current status of PPIs and IPPs in plants and discusses their potential in osmotic stress signalling and drought.