Regional expression of the rice KN1-type homeobox gene family during embryo, shoot, and flower development

We report the isolation, sequence, and pattern of gene expression of member s of the KNOTTED1 (KN1)-type class 1 homeobox gene family from rice. Phylog enetic analysis and mapping of the rice genome revealed that all of the ric e homeobox genes that we have isolated have one or two direct homologs in m aize, Of the homeobox genes that we tested, all exhibited expression in a r estricted region of the embryo that defines the position at which the shoot apical meristem (SAM) would eventually develop, prior to visible organ for mation. Several distinct spatial and temporal expression patterns were obse rved for the different genes in this region. After shoot formation, the exp ression patterns of these homeobox genes were variable in the region of the SAM, These results suggest that the rice KN1-type class 1 homeobox genes f unction cooperatively to establish the SAM before shoot formation and that after shoot formation, their functions differ.