These authors contributed equally to this work.
Two distinct high-affinity sulfate transporters with different inducibilities mediate uptake of sulfate in Arabidopsis roots
Article first published online: 14 FEB 2002
The Plant Journal
Volume 29, Issue 4, pages 465–473, February 2002
How to Cite
Yoshimoto, N., Takahashi, H., Smith, F. W., Yamaya, T. and Saito, K. (2002), Two distinct high-affinity sulfate transporters with different inducibilities mediate uptake of sulfate in Arabidopsis roots. The Plant Journal, 29: 465–473. doi: 10.1046/j.0960-7412.2001.01231.x
- Issue published online: 14 FEB 2002
- Article first published online: 14 FEB 2002
- Received 20 August 2001; revised 1 November 2001; accepted 21 November 2001.
- sulfate transporter;
- sulfate uptake;
- sulfur assimilation;
- sulfur limitation;
- Arabidopsis thaliana
Sulfate transporters present at the root surface facilitate uptake of sulfate from the environment. Here we report that uptake of sulfate at the outermost cell layers of Arabidopsis root is associated with the functions of highly and low-inducible sulfate transporters, Sultr1;1 and Sultr1;2, respectively. We have previously reported that Sultr1;1 is a high-affinity sulfate transporter expressed in root hairs, epidermal and cortical cells of Arabidopsis roots, and its expression is strongly upregulated in plants deprived of external sulfate. A novel sulfate transporter gene, Sultr1;2, identified on the BAC clone F28K19 of Arabidopsis, encoded a polypeptide of 653 amino acids that is 72.6% identical to Sultr1;1 and was able to restore sulfate uptake capacity of a yeast mutant lacking sulfate transporter genes (Km for sulfate = 6.9 ± 1.0 µm). Transgenic Arabidopsis plants expressing the fusion gene construct of the Sultr1;2 promoter and green fluorescent protein (GFP) showed specific localization of GFP in the root hairs, epidermal and cortical cells of roots, and in the guard cells of leaves, suggesting that Sultr1;2 may co-localize with Sultr1;1 in the same cell layers at the root surface. Sultr1;1 mRNA was abundantly expressed under low-sulfur conditions (50–100 µm sulfate), whereas Sultr1;2 mRNA accumulated constitutively at high levels under a wide range of sulfur conditions (50–1500 µm sulfate), indicating that Sultr1;2 is less responsive to changes in sulfur conditions. Addition of selenate to the medium increased the level of Sultr1;1 mRNA in parallel with a decrease in the internal sulfate pool in roots. The level of Sultr1;2 mRNA was not influenced under these conditions. Antisense plants of Sultr1;1 showed reduced accumulation of sulfate in roots, particularly in plants treated with selenate, suggesting that the inducible transporter Sultr1;1 contributes to the uptake of sulfate under stressed conditions.