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Evidence of an auxin‐mediated phosphoinositide turnover and an inositol (1,4,5)trisphosphate effect on isolated membranes of Daucus carota L.
Author(s) -
Zbell Bernd A.,
WalterBack Cornelia,
Bucher Hubert
Publication year - 1989
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240400309
Subject(s) - auxin , inositol , biochemistry , membrane , inositol trisphosphate , inositol phosphate , chemistry , daucus carota , vesicle , biology , receptor , botany , gene
Microsomal membranes from carrot suspension cells were phosphorylated in vitro with [γ‐ 32 P]ATP. In the presence of submicromolar concentrations of the natural auxin indoleacetic acid (IAA), a rapid, but transient decrease of the [ 32 P] label could be detected in the phospholipid extracts of the membranes. The phytohormone effect was not the result of an inhibition of the lipid phosphorylation reactions, but was caused by a simultaneous release of water‐soluble compounds, which, according to their chromatographic properties, were assumed to contain inositol polyphosphates. Although the [ 32 P]‐labeled lipids, as well as the inositol polyphosphates, were not identified unequivocally by chemical analysis, these findings point to an auxin‐mediated control of a phosphoinositidase C‐like reaction similar to the hormone‐stimulated phosphoinositide response in animals. Exogenously applied inositol (1,4,5)trisphosphate [(1,4,5)IP 3 ] was found to release 45 Ca 2+ from preloaded membrane vesicles of carrot cells. Both the detection of the auxin‐stimulated phosphoinositide response and the (1,4,5)IP 3 ‐mediated Ca 2+ release on isolated cell membranes offer new experimental approaches for the identification of the putative auxin receptor and its signal transduction pathway.