The invention relates to fusion proteins capable of acting as transcriptional repressors of cytokinin signaling, to polynucleotides encoding these fusion proteins, to vectors and cells comprising these polynucleotides, and to transgenic plants and parts thereof comprising these polynucleotides, vectors, and cells. The invention further relates to a process for making these transgenic plants and to the use of these transgenic plants for producing seeds of enhanced size, with enhanced seed filling, with reduced seed loss and/or with more rapid germination, and/or for producing a live root system with increased root mass, root length and/or root branching. The invention also relates to a method for enhancing the seed size, for enhancing seed filling, for reducing seed loss, and/or for reducing germination time and/or reproduction time, and/or for enhancing the root mass, root length and/or root branching of a plant and to seeds obtainable by the methods of the present invention.