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Expression of potassium‐transporter coding genes, and kinetics of rubidium uptake, along a longitudinal root axis
Author(s) -
VALLEJO AUGUSTO J.,
PERALTA MARIA LUISA,
SANTAMARIA GUILLERMO E.
Publication year - 2005
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2005.01334.x
Subject(s) - rubidium , tetraethylammonium , kinetics , transporter , potassium , hordeum vulgare , methylamine , chemistry , xylem , biophysics , divalent , biology , gene , biochemistry , botany , poaceae , physics , organic chemistry , quantum mechanics
The pattern of mRNA accumulation of genes coding for the putative potassium transporters HvHAK1A, HvHAK1B, HvHAK2, HvHAK3 and HvAKT1 along seminal roots was studied in K + starved barley ( Hordeum vulgare ) plants. Accumulation of these transcripts was lower in young, relative to older root zones, indicating the existence of a coordinated spatial pattern of gene regulation. A study of rubidium (Rb + ) uptake kinetics showed that for all root zones transport can be dissected into a linear and a saturable component. Paralleling the pattern of mRNA accumulation the V max of the saturable term was lowest in the youngest root zone. No differences in the Rb + K m or in the linear term were observed among root zones. K + channel blockers Ba 2+ , Al 3+ , and tetraethylammonium exerted no effect on Rb + uptake from diluted Rb + solutions, while it was inhibited by Cs + , NH 4 + , methylamine, and K + in all root zones. These results show that high‐affinity Rb + transport over the entire axis is mediated by transporters displaying HAK1‐like properties. The observation of a differential effect of Na + on Rb + uptake along roots is compatible with a change in the proportion and/or the activity of those transport entities following a longitudinal gradient.