Spermine stimulation of phospholipase C fromCatharanthus roseus transformed roots

Polyamines (Pas) are aliphatic amines that are ubiquitous in all living organisms and regulate a broad spectrum of physiological processes. It has been suggested that they can act through a signal transduction pathway. Using Catharanthus roseus hairy roots as a model we determined the levels of Pas throughout a culture cycle. We found that there is a peak in the intracellular concentration of Pas during the first six days of culture. The effect of Pas on phospholipase C (PLC) activity was also investigated. Putrescine, spermidine and spermine were added in vitro to the PLC assay. Putrescine did not modify PLC activity; spermidine inhibited the enzyme but at very high, non-physiological concentrations; and spermine increased the PLC activity four-fold at physiological concentrations. Our results suggest that spermine could regulate root growth by regulating the PLC signal transduction mechanism.