Hormone perception and signaling pathways have a fundamental regulatory function in the physiological processes of plants. Cytokinins, a class of plant hormones, regulate cell division and meristem maintenance. The cytokinin signaling pathway is well established in the model plant Arabidopsisthaliana. Several negative feedback mechanisms, tightly controlling cytokinin signaling output, have been described previously. In this study, we identified a new feedback mechanism executed through alternative splicing of the cytokinin receptor AHK4/CRE1. A novel splicing variant named CRE1int7 results from seventh intron retention, introducing a premature termination codon in the transcript. We showed that CRE1int7 is translated in planta into a truncated receptor lacking the C-terminal receiver domain essential for signal transduction. CRE1int7 can bind cytokinin but cannot activate the downstream cascade. We present a novel negative feedback mechanism of the cytokinin signaling pathway, facilitated by a decoy receptor that can inactivate canonical cytokinin receptors via dimerization and compete with them for ligand binding. Ensuring proper plant growth and development requires precise control of the cytokinin signaling pathway at several levels. CRE1int7 represents a so-far unknown mechanism for fine-tuning the cytokinin signaling pathway in Arabidopsis.

Department of Chemical Biology Faculty of Science Palacký University Šlechtitelů 27 783 71 Olomouc Czech Republic

Department of Molecular Biology Centre of the Region Haná for Biotechnological and Agricultural Research Faculty of Science Palacký University Šlechtitelů 27 783 71 Olomouc Czech Republic

Institute of Experimental Botany of the Czech Academy of Sciences Centre of Plant Structural and Functional Genomics Šlechtitelů 31 779 00 Olomouc Czech Republic

Institute of Science and Technology Austria 3400 Klosterneuburg Austria

Laboratory of Growth Regulators Faculty of Science of Palacký University and Institute of Experimental Botany AS CR Šlechtitelů 27 783 71 Olomouc Czech Republic

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