Auxin identification

Ichikawa, T. et al. (1997). Identification and role of adenylyl cyclase in auxin signalling in higher plants. Nature (London) 390,698-701. 

Palme, K., Feldwisch, J., Peters, W.S., Schell, J., Zettl, R., Campos, N., Felle, H. (1992). Auxin binding proteins are located in the ER and in the plasma membrane Identification by photoaffinity-labelling and characterization. Progress in Plant Growth Regulation (Karssen, C.M., Van Loon, L.C., Vreugdenhil, D., Eds.), pp. 73-81. Kluwer Academic, The Netherlands. 

Among the most noticeable findings from the research on plant hormones, the identification of receptors and receptor genes must be emphasized. In the last decade, since the publication of the previous edition of the book Comprehensive Natural Products Chemistry,5 the receptors and the receptor genes for ethylene, BRs, cytokinins, auxins, GAs, and abscisic acid have been identified, as described in the section for each plant hormone. 

Ten years after the initial identification of the tirl-1 mutant, its central role in the auxin signaling pathway has been revealed and with this the identification of a novel class of intracellular receptors. However, several early auxin responses occur too rapidly after auxin treatment to be caused by transcriptional changes and de novo protein synthesis. This, together with the fact that tirl/afbl—3 higher order mutants still seem to possess auxin responses,163 points to further auxin signaling routes waiting to be discovered. 

A number of investigators have taken a genetic approach to the identification of genes and proteins involved in auxin response, particularly in Arabidopsis [47]. The sensitivity of Arabidopsis seedlings to low concentrations of exogenous auxin has been the basis for extensive screens for auxin response mutants. At least nine genes have been defined in these screens and four have been characterized at the molecular level (Table 1). The product of the AUXl gene probably functions in cellular auxin influx and will not be discussed further here [56]. 

The major breakthroughs in the biochemical identification of ethylene receptors occurred almost simultaneously. It had been assumed that the methods used in receptor studies for auxins and other hormones would be inappropriate for ethylene. Thus, the displacement assays used for auxins seemed unlikely to work in the case of ethylene, firstly because bound ethylene would dissipate before it could be measured, and secondly because only relatively low specific activity labelled ethylene is possible. This situation would be exacerbated given the likely low abundance of receptors. 

The first study relates to the identification and design of novel herbicides and plant growth regulators that act by inhibiting polar transport of the plant hormone auxin (100). Previous studies (101) had identified seven auxin transport inhibitors, from which it was possible to describe a three-component... 

Chemical Genetics, Target Site Identification, Resistant Mutants, Herbicide Mode of Action, Auxins, Arahidopsis... 

The use of GC-MS offers the opportunity for unequivocal identification of auxins. The very specific and sensitive detection of trace amounts obtained with this technique allows accurate and precise measurements of lAA levels in plants. This great potential can be exploited only by taking specific precaution for handling and analyzing the samples. By the use of modern method of preparative separation and a well-chosen internal standard (IS), meaningful physiological correlation can be established. 

In MS of auxins, the widest used method of ionizing was by electron impact (El). The development and improvement of chemical ionization (PCI and NCI) have accumulated new evidence for identification of endogenous auxins and also has extended lAA detection to a lower limit [33, 34]. 

In all auxin work the low concentrations of the hormone have required that heavy reliance be placed on this identification by bioassay, more recently combined with paper or column chromatography. The evidence is thus frequently insecure and interpretation of the results may vary. 

Acton GJ, Murray PB (1974) The roles of auxin and gibberellin in reversing radiation inhibition of hypocotyl lengthening. Planta 117 219-226 Adams DO, Yang SF (1979) Ethylene biosynthesis identification of 1-amino-cyclopropane-1-carboxylic acid as an intermediate in the conversion of methionine to ethylene. Proc Natl Acad Sci USA 76 170-174... 

Bridges IG, Hillman JR, Wilkins MB (1973) Identification and localisation of auxin in primary roots of Zea mays by mass spectroscopy. Planta 115 189-192 Briggs WR, Steeves TA, Sussex IM, Wetmore RH (1955) A comparison of auxin destruction by tissue extracts and intact tissues of the fern Osmunda cinnamomea L. Plant Physiol 30 148-155... 

Greenwood MS, Goldsmith MHM (1970) Polar transport and accumulation of indole-3-acetic acid during root regeneration by Firms lambertiana embryos. Planta 95 297-313 Greenwood MS, Hillman JR, Shaw S, Wilkins MB (1973) Localisation and identification of auxin in roots of Zea mays. Planta 109 369-374 Gregory FG, Hancock CR (1955) The rate of transport of natural auxin in woody shoots. Ann Bot 19 451-465... 

Hall SM, Medlow GC (1974) Identification of lAA in phloem and root pressure saps of Ricinus communis L. by mass spectrometry. Planta 119 257-261 Halliday MBW, Wangermann E (1972 a) Leaf abscission in Coleus. I. Abscission zone formation and the effect of auxin on abscission. New Phytol 71 649-663 Halliday MBW, Wangermann E (1972b) Leaf abscission in Coleus. II. The distribution and fate of [ " C]-indolylacetic acid in the petiole. New Phytol 71 665-670 Hare RC (1964) Indoleacetic acid oxidase. Bot Rev 30 129-165... 

Rivier L, Pilet PE (1974) Indolyl-3-acetic acid in cap and apex of maize roots identification and quantification by mass fragmentography. Planta 120 107-112 Robinson BJ, Forman M, Addicott FT (1968) Auxin transport and conjugation in cotton explants. Plant Physiol 43 1321-1323... 

Libbert E, Risch H (1969) Interactions between plants and epiphytic bacteria regarding their auxin metabolism. V. Isolation and identification of the lAA-producing and -destroying bacteria from pea plants. Physiol Plant 22 51-58... 

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