Effect of hormones and spermidine on the turnover of inositolphospholipids in Brassica seedlings

Abstract

The effect of hormones (NAA and BAP) and a polyamine (spermidine) on the turnover of inositolphospholipids has been studied in Brassica oleracea seedlings. Incubation of hypocotyls for 4 hr with the hormones resulted in a significant decrease in the levels of labelled phosphatidylinositol 4,5 - bisphosphate (PIP₂), phosphatidylinositol 4 - phosphate (PIP) and phosphatidylinositol (PI), whereas the inositol 1,4 - bisphosphate (IP₂) and inositol 1,4,5 - trisphosphate (IP₃) level increased by 26%. An increase in PIP and PIP₂ accompanied by a decrease in PI, IP₂ and IP₃ level was observed when hypocotyls were treated with spermidine. Treatment with a combination of hormones and polyamine evoked a fast turnover of inositolphospholipids, showing an appreciable decrease in PIP₂, PIP and PI with a corresponding increase in IP₂ and IP₃ level. It is suggested that hormones act mainly on PIP₂ and induce its breakdown to produce IP₂ and IP₃ and 1,2 - diacylglycerol (DAG), to induce various biological responses.