INOSITOL(1,4,5)TRISPHOSPHATE PRODUCTION IN PLANT-CELLS - STIMULATION BY THE VENOM PEPTIDES, MELITTIN AND MASTOPARAN

The ability of the amphiphilic peptides, melittin and mastoparan,to mo dulate the production of inositol(1,4,5)trisphosphate in cultured plan t (Daucus carota L.) cells was investigated. When added to intact cell s melittin and mastoparan caused a rapid and dose-dependent increase i n inositol(1,4,5)trisphosphate concentrations. In isolated protoplasts , inositol(1,4,5)trisphosphate levels were 12 to 16-fold higher than i n the corresponding cells and neither melittin nor mastoparan was able to significantly affect inositol(1,4,5)trisphosphate production. Meli ttin and mastoparan had a strong inhibitory effect (IC50: 20 mu M) on the activity of polyphosphoinositide-specific phospholipase C in purif ied plasma membranes. These results demonstrate that the plant phospho inositide system can be activated by amphiphilic peptides in a manner analogous to that observed in specialized mammalian cells but that imp ortant functional components are altered, or lost, by the disruption o f the intact cell state. (C) 1994 Academic Press, Inc.