We have discovered a new gene in the model laboratory plant Arabidopsis thaliana that is involved in sepal and petal development. It encodes a transcription factor that apparently acts by repressing growth in the inter-sepal zone of flowers where petals arise. We now aim to determine how this growth suppression occurs, and whether it extends to leaves where the gene is also expressed. Control of the initiation and sculpturing of plant organs by site-specific inhibition of growth is a newly discovered mechanism that may be useful in manipulating plant architecture.