Over-expression of Brassica napus phosphatidylinositol-phospholipase C2 in canola induces significant changes in gene expression and phytohormone distribution patterns, enhances drought tolerance and promotes early flowering and maturation.

Phosphatidylinositol-specific phospholipase C (PtdIns-PLC2) plays a central role in the phosphatidylinositol-specific signal transduction pathway. It catalyses the hydrolysis of membrane-bound phosphatidylinositol 4,5-bisphosphate to produce two second messengers, sn-1,2-diacylglycerol and inositol 1,4,5-trisphosphate. The former is a membrane activator of protein kinase C in mammalian systems, and the latter is a Ca(2+) modulator which induces distinctive oscillating bursts of cytosolic Ca(2+), resulting in regulation of gene expression and activation of proteins. Sustained over-expression of BnPtdIns-PLC2 in transgenic Brassica napus lines brought about an early shift from vegetative to reproductive phases, and shorter maturation periods, accompanied by notable alterations in hormonal distribution patterns in various tissues. The photosynthetic rate increased, while stomata were partly closed. Numerous gene expression changes that included induction of stress-related genes such as glutathione S-transferase, hormone-regulated and regulatory genes, in addition to a number of kinases, calcium-regulated factors and transcription factors, were observed. Other changes included increased phytic acid levels and phytohormone organization patterns. These results suggest the importance of PtdIns-PLC2 as an elicitor of a battery of events that systematically control hormone regulation, and plant growth and development in what may be a preprogrammed mode.