Figure 9.

Sulfate uptake activities are increased by short-term sulfur starvation in 35S:SULTR1;1mycHis and 35S:SULTR1;2mycHis plants. The experiments were carried out in the same transgenic lines used for the RT-PCR (Fig. 7) and protein-blot analysis (Fig. 8). 35S:SULTR1;1mycHis lines (1;1ox-1 and 1;1ox-2), 35S:SULTR1;2mycHis lines (1;2ox-11 and 1;2ox-15), and Ws wild-type plants were grown for 12 d on agar medium containing 1,500 μm sulfate (+S; black bars), and then incubated for 24 h on agar medium without sulfur source (−S; white bars). Sulfate uptake activities were measured in 5 μm ³⁵SO₄²⁻ liquid medium as described in Figure 2C (means ± ses, n = 10). Induction of sulfate uptake by 24-h sulfur starvation was statistically significant (P < 0.00001, Student's t test) in all transgenic lines and wild-type plants. Statistical differences among the wild type and transgenic lines were calculated for +S and −S conditions independently by one-way ANOVA. Different letters indicate means that were statistically different by Tukey's multiple-testing method (P < 0.05).