Different forms of phospholipase D (dependent on and independent of the presence of phospha-tidylinositol 4,5-bisphosphate, PIP2) were identified in maturing and germinating seeds of Brassica napus. Both forms were present in cytosolic and membrane fractions of maturing seeds. PIP2-dependent activity increased continuously during seed germination, while PIP2-independent activity appeared mostly at the very beginning of seed maturation. PIP2-dependent activity was detected mainly in the plasma-membrane fraction. Phosphatidylinositol-specific phospholipase C (PI-PLC) was found only in membrane fractions of both types of developing rape seed tissues. The increasing activities of PLC and PIP2-dependent PLD were mainly detected in hypocotyls of seedlings. Some biochemical characteristics of both described enzymes are also presented.
A Flower-Specific Phospholipase D Is a Stigmatic Compatibility Factor Targeted by the Self-Incompatibility Response in Brassica napus