Inhibition of the plant cytokinin transduction pathway by bacterial histidine kinase inhibitors in Catharanthus roseus cell cultures

We describe the isolation of two Catharanthus roseus cDNAs encoding proteins putatively involved in the final steps of a ‘histidine-to-aspartate’ phosphorelay in cytokinin (CK) signaling. The expression of one of these genes, CrRR1, was specifically up-regulated by CKs in C. roseus cell suspensions. We used this system as a biological model to test the activity of bacterial histidine kinase inhibitors. Our data demonstrate that these inhibitors are active on the CK transduction pathway and represent powerful chemical tools to study hormone signal transduction in plants. Moreover, these data suggest a strong conservation of functional features between prokaryotic and plant signaling pathways utilizing histidine kinases.