The roles of three functional sulphate transporters involved in uptake and translocation of sulphate in Arabidopsis thaliana.
To investigate the uptake and long-distance translocation of sulphate in plants, we have characterized three cell-type-specific sulphate transporters, Sultr1;1, Sultr2;1 and Sultr2;2 in Arabidopsis thaliana. Heterologous expression in the yeast sulphate transporter mutant indicated that Sultr1;1 encodes a high-affinity sulphate transporter (Km for sulphate 3.6 +/- 0.6 microM), whereas Sultr2;1 and Sultr2;2 encode low-affinity sulphate transporters (Km for sulphate 0.41 +/- 0.07 mM and >/= 1.2 mM, respectively). In Arabidopsis plants expressing the fusion gene construct of the Sultr1;1 promoter and green fluorescent protein (GFP), GFP was localized in the lateral root cap, root hairs, epidermis and cortex of roots. beta-glucuronidase (GUS) expressed with the Sultr2;1 promoter was specifically accumulated in the xylem parenchyma cells of roots and leaves, and in the root pericycles and leaf phloem. Expression of the Sultr2;2 promoter-GFP fusion gene showed specific localization of GFP in the root phloem and leaf vascular bundle sheath cells. Plants continuously grown with low sulphate concentrations accumulated high levels of Sultr1;1 and Sultr2;1 mRNA in roots and Sultr2;2 mRNA in leaves. The abundance of Sultr1;1 and Sultr2;1 mRNA was increased remarkably in roots by short-term stress caused by withdrawal of sulphate. Addition of selenate in the sulphate-sufficient medium increased the sulphate uptake capacity, tissue sulphate content and the abundance of Sultr1;1 and Sultr2;1 mRNA in roots. Concomitant decrease of the tissue thiol content after selenate treatment was consistent with the suggested role of glutathione (GSH) as a repressive effector for the expression of sulphate transporter genes.
Laboratory of Molecular Biology and Biotechnology, Research Center of Medicinal Resources, Faculty of Pharmaceutical Sciences, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan.
H
H
Takahashi
A
A
Watanabe-Takahashi
F W
FW
Smith
M
M
Blake-Kalff
M J
MJ
Hawkesford
K
K
Saito
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D007700:Kinetics; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D000076988:Sulfate Transporters; D013431:Sulfates / Q000378:metabolism*
D002352:Carrier Proteins; D017931:DNA Primers; D026901:Membrane Transport Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters; D013431:Sulfates