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Enhanced salt tolerance mediated by AtHKT1 transporter‐induced Na + unloading from xylem vessels to xylem parenchyma cells
Author(s) -
Horie Tomoaki,
Motoda Jo,
Kubo Masahiro,
Yang Hua,
Yoda Kinya,
Horie Rie,
Chan WaiYin,
Leung HoYin,
Hattori Kazumi,
Konomi Mami,
Osumi Masako,
Yamagami Mutsumi,
Schroeder Julian I.,
Uozumi Nobuyuki
Publication year - 2005
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2005.02595.x
Subject(s) - xylem , parenchyma , biophysics , phloem , chemistry , microbiology and biotechnology , immunoelectron microscopy , biology , botany , antibody , immunology
Summary AtHKT1 is a sodium (Na + ) transporter that functions in mediating tolerance to salt stress. To investigate the membrane targeting of AtHKT1 and its expression at the translational level, antibodies were generated against peptides corresponding to the first pore of AtHKT1. Immunoelectron microscopy studies using anti‐AtHKT1 antibodies demonstrate that AtHKT1 is targeted to the plasma membrane in xylem parenchyma cells in leaves. AtHKT1 expression in xylem parenchyma cells was also confirmed by AtHKT1 promoter–GUS reporter gene analyses. Interestingly, AtHKT1 disruption alleles caused large increases in the Na + content of the xylem sap and conversely reduced the Na + content of the phloem sap. The athkt1 mutant alleles had a smaller and inverse influence on the potassium (K + ) content compared with the Na + content of the xylem, suggesting that K + transport may be indirectly affected. The expression of AtHKT1 was modulated not only by the concentrations of Na + and K + but also by the osmolality of non‐ionic compounds. These findings show that AtHKT1 selectively unloads sodium directly from xylem vessels to xylem parenchyma cells. AtHKT1 mediates osmolality balance between xylem vessels and xylem parenchyma cells under saline conditions. Thus AtHKT1 reduces the sodium content in xylem vessels and leaves, thereby playing a central role in protecting plant leaves from salinity stress.