Changes in inositol phosphates in wild carrot cells upon initiation of cell wall digestion

Previous studies have shown that inositol trisphosphate (IP3) stimulated 45Ca+2 efflux from fusogenic carrot protoplasts and it was suggested that IP3 may serve as a second messenger for the mobilization of intracellular Ca+2 in higher plant cells. To determine whether or not inositol phosphate metabolism changes in response to external stimuli, the cells were labeled with myo-[2-3H] inositol for 18 h and exposed to cell wall digestion enzymes, Driselase. The inositol phosphates were extracted with ice cold 10% TCA and separated by anion exchange chromatography. The radioactivity of the fraction that contained IP3 increased 2-3.8 fold and that which contained inositol bisphosphate increased 1.9-2.6 fold within 1.5 min of exposure to Driselase. After 6 min, the radioactivity of both fractions increased 6-7.7 fold and an increase in inositol monophosphate was observed. These data indicate that inositol phosphate metabolism is stimulated by Driselase and suggest polyphosphoinositide hydrolysis occurs upon initiation of cell wall digestion