Yoshida K T, Wada T, Koyama H, Mizobuchi-Fukuoka R, Naito S
Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
Plant Physiol. 1999 Jan;119(1):65-72. doi: 10.1104/pp.119.1.65.
Myo-inositol-1-phosphate (I[1]P) synthase (EC 5.5.1.4) catalyzes the reaction from glucose 6-phosphate to I(1)P, the first step of myo-inositol biosynthesis. Among the metabolites of I(1)P is inositol hexakisphosphate, which forms a mixed salt called phytin or phytate, a storage form of phosphate and cations in seeds. We have isolated a rice (Oryza sativa L.) cDNA clone, pRINO1, that is highly homologous to the I(1)P synthase from yeast and plants. Northern analysis of total RNA showed that the transcript accumulated to high levels in embryos but was undetectable in shoots, roots, and flowers. In situ hybridization of developing seeds showed that the transcript first appeared in the apical region of globular-stage embryos 2 d after anthesis (DAA). Strong signals were detected in the scutellum and aleurone layer after 4 DAA. The level of the transcript in these cells increased until 7 DAA, after which time it gradually decreased. Phytin-containing particles called globoids appeared 4 DAA in the scutellum and aleurone layer, coinciding with the localization of the RINO1 transcript. The temporal and spatial patterns of accumulation of the RINO1 transcript and globoids suggest that I(1)P synthase directs phytin biosynthesis in rice seeds.
肌醇 -1 - 磷酸（I[1]P）合酶（EC 5.5.1.4）催化从6 - 磷酸葡萄糖生成I(1)P的反应，这是肌醇生物合成的第一步。I(1)P的代谢产物之一是肌醇六磷酸，它形成一种称为植酸钙镁或植酸盐的混合盐，是种子中磷酸盐和阳离子的储存形式。我们分离出了一个水稻（Oryza sativa L.）cDNA克隆，pRINO1，它与酵母和植物中的I(1)P合酶高度同源。对总RNA的Northern分析表明，该转录本在胚中积累到高水平，但在茎、根和花中检测不到。对发育种子的原位杂交显示，该转录本在开花后2天（DAA）首次出现在球形期胚的顶端区域。4 DAA后在盾片和糊粉层中检测到强信号。这些细胞中转录本的水平一直增加到7 DAA，之后逐渐下降。称为球状体的含植酸钙镁颗粒在4 DAA时出现在盾片和糊粉层中，与RINO1转录本的定位一致。RINO1转录本和球状体积累的时间和空间模式表明，I(1)P合酶指导水稻种子中的植酸钙镁生物合成。
