The homologous gene of the maize Vp1 gene was isolated from rice (Oryza sativa). Sequence analysis revealed that the rice Vp1 gene (Osvp1) encodes a protein of 728 amino acids and is interupted by 5 introns at positions identical to those of the maize gene. Osvp1 transcript was detected in developing embryo as early as 10 days after flowering and decreased toward maturity. Osvp1 transcript was also detected in dry as well as imbided mature embryos. The ability of Osvp1 gene product to activate a target gene was shown by transient expression experiments in rice suspension-cultured cell protoplasts using a reporter gene construct carrying the bacterial beta-glucuronidase (GUS) gene fused to the promoter of OsEm gene, the rice homologue of the wheat Em gene.