Differential effects of a transgene to confer low phytic acid in caryopses located at different positions in rice panicles.

In previous studies, we attempted to reduce phytic acid in rice seeds by silencing the 1d-myo-inositol 3-phosphate synthase gene, RINO1, using an antisense sequence under the control of the rice glutelin GluB-1 promoter. The stable transgenic line showed a weak low phytic acid phenotype. In this study, we show that the position of the caryopsis in the panicle might affect the level of gene silencing through a difference in temporal and spatial expression patterns between RINO1 and GluB-1 promoters, resulting in a large variation in Pi levels and a small increase in Pi in the transgenic seeds.