knotted1 (kn1) and related homeobox genes in plants are expressed in and around the shoot apical meristem (SAM), where they are thought to be involved in maintenance of the SAM and/or the development of lateral organs. On pages 1651 to 1663 in this issue, Sentoku et al. report the isolation, sequence, and expression patterns of the rice OSH family of kn1-related genes. In situ hybridization experiments, including the one on the cover showing OSH43 expression in the corpus of the inflorescence meristem, demonstrate that prior to visible organ formation, all OSH genes are expressed in a restricted domain of the embryo-the region within which the SAM will eventually form. Following shoot formation, however, the expression patterns of the OSH genes vary from region to region in the SAM. These results suggest that OSH genes function cooperatively to establish the SAM before shoot formation but that their functions differ thereafter.