An Escherichia coli phytase gene was introduced into Arabidopsisplants using an embryo-specific promoter and a signal peptide for vacuolar targeting. Three independent transgenic lines were analysed. Phytase activity in dry seeds was observed in transgenic lines, whereas no activity was detected in control, untransformed seeds. Transgenic seeds expressing the phytase gene had lower levels of phytic acid than the controls. Concomitant with the decrease in phytic acid was an increase in free phosphate. These results indicated that embryo-expressed phytase can reduce the levels of phytic acid stored during development.