Abstract
Phytic acid (inositol hexakisphosphate ; IP6), a storage compound of phosphorus, is accumulated in protein storage vacuole during seed maturation. Recently IP6 was reported to be in crystal of TIR1, auxin receptor of Arabidopsis, suggesting that IP6 might be related to auxin signaling. The synthetic mechanism of IP6 is, however, still unclear in higher plants. To confirm the subcellular distribution of enzymes for inositol phosphate synthesis, we expressed the GFP fusion proteins transiently in Arabidopsis cultured cells. We observed fluorescence of all GFP-tagged enzymes in the cytosolic space. This suggests that IP6 may be synthesized in the cytosol. In various plants it is revealed that IP6 is localized in vacuole and endoplasmic reticulum. To clarify IP6 localization in Arabidopsis cells, we isolated the vacuoles and protoplasts and determined the IP6 concentration in them. We also analyzed interactions among enzymes for inositol phosphate synthesis.
