1. Supplementary figure 1 Colorimetric analysis of inorganic P by molybdenium staining of hydrochloric extracts of rice grains in rice grains (non-embryo half). Left: 1A to 1D and 7E to 7H: P standards at amounts of 0.155μg, 0.465μg, 0.93μg, and 1.395μg, respectively; 2A to 2H: Os-lpa-XS110-1; 3A to 3H: Os- lpa-XS110-2; 4A to 4H: heterozygous Os-lpa-XS110-3; 5A to 5E and 6A to 6E: T 1 seeds of T-DNA activation tagging line 4A-02500; 7A to 7D: Dongjin (parental variety of 4A-02500 ). Right: 8A-8E, P standards at amounts of 0.00, 0.155μg, 0.465μg, 0.93μg, and 1.395μg, respectively; 9A to 9H: XS110; 10A to 10H: Os-lpa-XS110-2; 11A to 11H: homozygous Os-lpa-XS110-3; 12A to 12H, 13A to 13H, 14A to 14H, 15A to 15H, 16A to 16H and 17A to 17H; 18A to 18H, 19A to 19H: T 2 seeds from individual T 1 plants of 4A-02500 at T 2 generation.

2. Os-lpa-XS110-3 Xiushui 110 2468101214 retention time [min] 0 10 20 30 40 50 response [mV] 0 10 20 30 40 50 response [mV] InsP 6 0 10 20 30 40 50 response [mV] InsP 6 Os-lpa-XS110-2 Standard inositol phosphates Supplementary figure 2. HPLC of acid-soluble Ins phosphates in wild type Xiushui 110 and its two LPA mutants. InsP 6 is hexakisphosphate, or phytic acid. InsP 3, InsP 4, and InsP 5 are tri-, tetrakis- and pentakisphosphates, respectively.

3. WT M LPA RSBRSB WT M LPA RSBRSB Actin MRP5 bp 400 300 200 100 Supplementary figure 3. RT-PCR analysis of OsMRP5 gene using total RNA isolated from root (R), sheath (S) and blade (B) of 14-day old seedlings. M: DNA marker; WT: parent variety ‘Dongjing’; LPA: seedlings of low phytic acid seeds of T-DNA insertion lines at T 3 generation. RT-PCR was performed different tissues of. The actin gene was used as control.