Hyperosmotic stress induces rapid synthesis of phosphatidyl-D-inositol 3,5-bisphosphate in plant cells

Cells from several different plant species synthesised a polyphosphoinositi de (PPI)-like lipid when osmo-stressed, Synthesis was maximal after about 1 0 min and was stimulated by a variety of osmolytes. Using NaCl, the stronge st response centred around 200 mM, The lipid was shown to be the hovel PPI isomer phosphatidyl-inositol 3,5-bisphosphate [PtdIns(3,5)P-2] by analytica l thin-layer chromatography and conversion to PtdIns(3,4,5)P-3 using recomb inant phosphoinositide 4-OH kinase. The results indicate that PtdIns-(3,5)P -2 plays a role in a general osmo-signalling pathway in plants. Its potenti al role is discussed.