Specificity of the Arabidopsis Shoot and Root Response toCytokinins

Cytokinins (CK) have been implicated in regulation of many aspects of plant growth and development. Recent genetic studies suggest that CK play distinct and sometimes even opposite roles in the regulation of the shoot and root development in Arabidopsis. Here we present results of a comprehensive approach in the study of the differential shoot and root CK response. To analyze CK response six days old seedlings of Arabidopsis thaliana (Col-0) were treated with 5 uM CK N6-benzylaminopurine BAP and root and shoot tissues were analyzed separately on diverse levels. Interestingly we identified proteins associated with abscisic acid (ABA)-dependent regulations in shoots, while in roots we detected proteins linked with ethylene metabolism and signalling. To further substantiate the potential crosstalk of BAP with metabolism of other hormones, we have analyzed changes of the endogenous hormone levels after CK application. We observed strong tissue specificity caused by BAP application in endogenous levels of ABA and ACC, the rate-limiting precursor of the ethylene biosynthesis that corresponded to our results of the proteomic analysis.