OsiEZ1 cDNA is 3133 bp long with an ORF of 2799 bp, and the predicted amino acid sequence (895 residues) corresponds to a protein of ca. 98 kDa. All the characteristic domains known to be conserved in E(Z) homologs (subgroup I) of SET domain containing proteins are present in OsiEZ1. In the rice genome, a 7499 bp long OsiEZ1 sequence is split into 17 exons interrupted by 16 introns. Southern analysis indicates that OsiEZ1 is represented as single copy in the rice genome. Expression studies revealed that the OsiEZ1 transcript level was highest in rice flowers, almost undetectable in developing seeds of 1-2 days post-fertilization but increased significantly in young seeds of 3-5 days post-fertilization. The OsiEZ1 transcript was barely detectable in mature zygotic embryos, but its levels were significantly higher in callus derived from rice scutellum, somatic embryos and young seedlings. The OsiEZ1/GUS