title: Root-to-shoot transport of sulfate in Arabidopsis. Evidence for the role of SULTR3;5 as a component of low-affinity sulfate transport system in the root vasculature.
abstract: Xylem transport of sulfate regulates distribution of sulfur in vascular plants. Here, we describe SULTR3;5 as an essential component of the sulfate transport system that facilitates the root-to-shoot transport of sulfate in the vasculature. In Arabidopsis (Arabidopsis thaliana), SULTR3;5 was colocalized with the SULTR2;1 low-affinity sulfate transporter in xylem parenchyma and pericycle cells in roots. In a yeast (Saccharomyces cerevisiae) expression system, sulfate uptake was hardly detectable with SULTR3;5 expression alone; however, cells coexpressing both SULTR3;5 and SULTR2;1 showed substantial uptake activity that was considerably higher than with SULTR2;1 expression alone. The V(max) value of sulfate uptake activity with SULTR3;5-SULTR2;1 coexpression was approximately 3 times higher than with SULTR2;1 alone. In Arabidopsis, the root-to-shoot transport of sulfate was restricted in the sultr3;5 mutants, under conditions of high SULTR2;1 expression in the roots after sulfur limitation. These results suggested that SULTR3;5 is constitutively expressed in the root vasculature, but its function to reinforce the capacity of the SULTR2;1 low-affinity transporter is only essential when SULTR2;1 mRNA is induced by sulfur limitation. Consequently, coexpression of SULTR3;5 and SULTR2;1 provides maximum capacity of sulfate transport activity, which facilitates retrieval of apoplastic sulfate to the xylem parenchyma cells in the vasculature of Arabidopsis roots and may contribute to the root-to-shoot transport of sulfate.
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kataoka
authors.forename: Naomi
authors.initials: N
authors.lastname: Hayashi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamaya
authors.forename: Hideki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D027321:Anion Transport Proteins / Q000502:physiology*; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000502:physiology*; D001692:Biological Transport; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified; D018517:Plant Roots / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*
chemical_list: D027321:Anion Transport Proteins; D029681:Arabidopsis Proteins; C496081:SULTR3;5 protein, Arabidopsis; D013431:Sulfates