Scanning electron micrograph of a shoot apex of a transgenic Arabidopsis plant expressing DORNRÖSCHEN/ENHANCER OF SHOOT REGENERATION1 behind the CLAVATA3 promoter (Kirch et al., pages 694–705). Overexpression of DRN/ESR1, which encodes an AP2/ERF-type transcription factor, in the stem cell zone results in a highly enlarged shoot apex. The shoot meristem, resting on a ball-shaped shoot axis, is still able to initiate leaf primordia in a spiral phyllotaxy. However, during displacement to the periphery, these lateral organs fail to grow out and are overgrown by the massively enlarging shoot axis. Ectopic activity of the DRN/ESR1 transcription factor in the center of the shoot meristem therefore allows initiation of organ primordia, but interferes with their elaboration at the periphery of the shoot apex.