The analysis of phytic acid synthesis in Arabidopsis cultured cells.

Abstract

Phytic acid, inositol hexakisphosphate, IP6, a storage compound of phosphorus in seeds, is accumulated in protein storage vacuole during seed maturation. The synthesis and physiological function of IP6 are still unclear in higher plants. We succeeded in inducing synthesis of phytate in suspension-cultured Arabidopsis cells by Pi supplementation. It has been proposed that IP6 is finally synthesized by addition of a last phosphate group to inositol pentakisphosphate by one of inositol phosphate kinase ; IPK1. To confirm the subcellular distribution of AtIPK1, we expressed the GFP fusion protein transiently in Arabidopsis cultured cells. We observed fluorescence of GFP at the cytosol of cultured cells. It suggests that IP6s may be synthesized at the cytosol in Arabidopsis cultured cells, and then transported into the vacuole for storage.