Expression of genes in wild-type transgenic plants under normal Pi condition.

<p>Expression of central transporters affecting Pi absorption and homeostasis in WT and transgenic plants. Error bars indicate ±SD (n = 3). (**<i>p</i><0.01 and *<i>P</i><0.05, one-way ANOVA).</p

Function expression of <i>OsPT4</i> in yeast.

<p>The yeast cells were grown in solution that had been stained for acidification. The pH indicator, bromocresol purple, did not change from blue to yellow until the yeast cells had significant growth in culture. The medium contained 0 μM and 75 μM Pi, respectively. A: Color shifts in wild-type (WT), yeast strain <i>pho84</i> (control), and <i>pho84+OsPT4</i>, which express <i>OsPT4</i> in <i>pho84</i> grown on synthetic defined (SD) Ura mediums. B: Growth conditions of wild-type, <i>pho84</i>, and <i>pho84</i> transformed with pYES2-<i>OsPT4</i> generated in a 24-hour liquid culture under 0μM and 75μM Pi conditions. Statistically significant differences are indicated: **<i>p</i><0.01, Student’s one-way ANOVA analysis.</p

Tissue localization of <i>OsPT4</i>.

<p>GUS staining of transgenic plants harboring the <i>OsPT4</i> promoter. <i>GUS</i> fusion was observed. Expression of <i>OsPT4</i> was shown in different tissues of rice supplied with normal Pi for 21 days. A: Root tip. B: The junction between the meristematic and elongated zones. C: Branching of lateral root. D: Lateral root. E: Transverse section of root tip. F: Transverse section of root maturation zone. G and H: Enlarged images of (E) and (F). I: Ligule. J: Internodes of culm. K: Transverse section of culm. L: Caryopse and stamen. M: Leaf blade.</p

Characterization of wild-type and transgenic plants.

<p>A: Expression of OsPT4 in transgenic plants. Seven-day-old seedlings were transferred to nutrient solution for 2 weeks. RNA was extracted from the shoots of the seedling. Oe1, Oe2, Ri1, and Ri2 represented independent <i>OsPT4</i>-overexpressing and RNA interference lines. Relative expression levels are shown as percentages compared with wild-type shown as 100% expression. B, C, and D: Growth of wild-type and transgenic plants. Plants were grown in nutrient solutions to which 0 mM Pi (LP), 1.5 mM Pi (HP), and 0.3 mM Pi (CK) were added for 21 days. E–H: Phenotypic analysis of OsPT4 transgenic plants. Height, root length, number of main roots, and tiller numbers were obtained from the 21-day-old wild-type and transgenic plants grown in nutrient solutions with different Pi concentrations. Five plants per line were measured. I and J: The Pi concentration of shoots and roots in wild-type and transgenic plants. Data are means ± SD of five biological replicates. Values are significantly different from those of wild-type: *P<0.05 and **P<0.01. (one-way ANOVA).</p

Primers used in this study.

<p>Functional Complementation Assay of <i>OsPT4</i> in Yeast</p><p>Primers used in this study.</p

The Phosphate Transporter Gene <i>OsPht1;4</i> Is Involved in Phosphate Homeostasis in Rice

<div><p>A total of 13 phosphate transporters in rice (<i>Oryza sative</i>) have been identified as belonging to the <i>Pht1</i> family, which mediates inorganic phosphate (Pi) uptake and transport. We report the biological property and physiological role of <i>OsPht1;4</i> (<i>OsPT4</i>). Overexpressing <i>OsPT4</i> resulted in significant higher Pi accumulation in roots, straw and brown rice, and suppression of <i>OsPT4</i> caused decreased Pi concentration in straw and brown rice. Expression of the <i>β</i>-glucuronidase reporter gene driven by the <i>OsPT4</i> promoter showed that <i>OsPT4</i> is expressed in roots, leaves, ligules, stamens, and caryopses under sufficient Pi conditions, consistent with the expression profile showing that <i>OsPT4</i> has high expression in roots and flag leaves. The transcript level of <i>OsPT4</i> increased significantly both in shoots and roots with a long time Pi starvation. <i>OsPT4</i> encoded a plasma membrane—localized protein and was able to complement the function of the Pi transporter gene PHO84 in yeast. We concluded that <i>OsPT4</i> is a functional Pi-influx transporter involved in Pi absorption in rice that might play a role in Pi translocation. This study will enrich our understanding about the physiological function of rice <i>Pht1</i> family genes.</p></div

Pi concentration of the wild-type and transgenic plants in field.

<p>The rice including wild type and transgenic plants were grown in field. When plants grown to maturity, the phosphate concentration of straws and brown rice were measured. Data are means ± SD of five biological replicates. Values are significantly different from those of wild-type: *P<0.05 and **P<0.01. (one-way ANOVA).</p