Evidence of an auxin-mediated phosphoinositide turnover and an inositol (1,4,5)trisphosphate effect on isolated membranes of Daucus carota L.
✍ Scribed by Bernd A. Zbell; Cornelia Walter-Back; Hubert Bucher
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 629 KB
- Volume
- 40
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Microsomal membranes from carrot suspension cells were phosphorylated in vitro with [-p3'P]ATP. In the presence of submicromolar concentrations of the natural auxin indoleacetic acid (IAA), a rapid, but transient decrease of the ["PI 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 [32P]-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,] was found to release 4sCa2+ from preloaded membrane vesicles of carrot cells. Both the detection of the auxin-stimulated phosphoinositide response and the (1 ,4,5)IP3mediated Caz+ release on isolated cell membranes offer new experimental approaches for the identification of the putative auxin receptor and its signal transduction pathway.