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Root growth inhibition by NH 4 + in Arabidopsis is mediated by the root tip and is linked to NH 4 + efflux and GMPase activity
Author(s) -
LI QING,
LI BAOHAI,
KRONZUCKER HERBERT J.,
SHI WEIMING
Publication year - 2010
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.1365-3040.2010.02162.x
Subject(s) - elongation , efflux , arabidopsis , mutant , auxin , ammonium , chemistry , biophysics , stimulation , ethylene , cell division , cell growth , biochemistry , biology , microbiology and biotechnology , cell , materials science , gene , organic chemistry , neuroscience , metallurgy , ultimate tensile strength , catalysis
Root growth in higher plants is sensitive to excess ammonium (NH 4 + ). Our study shows that contact of NH 4 + with the primary root tip is both necessary and sufficient to the development of arrested root growth under NH 4 + nutrition in Arabidopsis . We show that cell elongation and not cell division is the principal target in the NH 4 + inhibition of primary root growth. Mutant and expression analyses using DR5:GUS revealed that the growth inhibition is furthermore independent of auxin and ethylene signalling. NH 4 + fluxes along the primary root, measured using the Scanning Ion‐selective Electrode Technique, revealed a significant stimulation of NH 4 + efflux at the elongation zone following treatment with elevated NH 4 + , coincident with the inhibition of root elongation. Stimulation of NH 4 + efflux and inhibition of cell expansion were significantly more pronounced in the NH 4 + ‐hypersensitive mutant vtc1‐1 , deficient in the enzyme GDP‐mannose pyrophosphorylase (GMPase). We conclude that both restricted transmembrane NH 4 + fluxes and proper functioning of GMPase in roots are critical to minimizing the severity of the NH 4 + toxicity response in Arabidopsis .