Inositol-containing lipids in suspension-cultured plant cells: an isotopic study

Polar lipids were extracted from suspension-cultured tomato (Lycopersicon esculentum Mill.) cells and analyzed by thin layer chromatography. Four major inositol-containing compounds were found, and incorporation of [(32)P]orthosphosphate, [2-(3)H]glycerol, and myo-[2-(3)H]inositol was studied. Results showed that phosphatidylinositol-monophosphate is the phospholipid in these cells displaying the most rapid incorporation of [(32)P]orthophosphate. We suggest that the tracer is incorporated primarily into the phosphomonoester group. Two inositol-containing lipids showed chromatographic behavior similar to phosphatidylinositol-4,5-bisphosphate when using standard thin layer chromatography techniques. The labeling pattern of these compounds, however, reveals that it is unlikely that either of these is identical to phosphatidylinositol-4,5-bisphosphate. Should phosphatidylinositol-bisphosphate be present in suspension cultured plant cells, our data indicate chemical abundancies substantially lower than previously reported.