Effects of Phosphatidic Acid on Cytokinin Signal Transduction in Periwinkle Cells

In periwinkle cell suspensions, the accurate quantification of gene expression through real-time RTPCR showed that two type-A response regulators (RR-A), considered primary cytokinin (CK)-responsive genes, were differentially regulated after CK treatment. Specific inhibition of phospholipase D (PLD)-dependent phosphatidic acid (PA) production by primary alcohols reduced significantly the transcript level of one gene in response to CK, although the other gene was unaffected. Moreover, this inhibitory effect on gene transcript level could be antagonized by exogenous supply of PA. These results suggest that PA, likely released from the membrane by PLD activity, could operate in the early steps of CK signalling in periwinkle cells.