A NEW FAMILY OF CYTOKININ RECEPTORS FROM CEREALES

The highly specific recognition of a natural cytokinin, trans-zeatin, by cytokinin-binding protein (CBP) of 67 kDa from barley leaves was de tected with an assay developed on the basis of cytokinin competition i n ELISA with anti-idiotype antibodies (raised against antibodies to ze atin) for complex formation with CBP. Monoclonal antibodies (mAbs) rai sed against 70 kDa CBP from etiolated maize seedlings cross-reacted wi th barley 67 kDa CBP and prevented barley CBP and trans-zeatin induced activation of transcription elongation directed by RNA polymerase I a ssociated with barley chromatin. One mAb (Z-6) had an agonistic effect , Maize CBP replaced barley CBP in activation of RNA synthesis with cy tokinin in the barley transcription system. Hence, a new family of cyt okinin receptors with common functions and immunodeterminants includin g maize and barley CBPs was found. (C) 1998 Federation of European Bio chemical Societies.