Protein auxins

Auxins, scopoletin, hydrocyanic acid, glucosides, glucosides, unidentified ninhydrin-positive compounds, unidentified soluble proteins, reducing compounds, ethanol, glycinebetaine, inositol and myo-inositol-like compounds, Al-induced polypeptides, dihydroquinone, sorgoleone... 

Detection and Localization of Auxin Protein Conjugates in Okra... 

Henderson J, Bauly JM, Ashford DA, Oliver SC, Hawes CR, Lazarus CM, Venis MA, Napier RM. Retention of maize auxin-binding protein in the endoplasmic reticulum quantifying escape and the role of auxin. Planta 1997 202 313-323. 

The induction of PAL activity by the two growth factors can be separated in time so that they may act at different sites within the cell to bring about the response (40). Auxin added at the time of subculture of the tissue changes the pattern of protein synthesis of the cells by changing the transcription pattern of the mRNA after two hours (43). Kinetin does not have this effect (44). 

An open question is whether auxin stimulates wall loosening by acting at the level of gene transcription. Auxin certainly stimulates the rate of RNA synthesis in plant section,454-456 isolated nuclei,457-459 and chromatin,457,460 and new protein species appear after treatment of intact tissues with the hormone.461-463 However, the findings of Haschemeyer464 and Evans and Ray465 strongly indicated that the induction of cell-wall exten-... 

Two aliphatic acids possess, for grasses, many of the growth-distortion and toxicity effects associated with the synthetic auxins on dicotyledonous plants. Trichloroacetic acid and 2,2-dichloropropionic acid (dalapon), as the sodium salts, have been called grass "hormones or auxins, although Wilkinson184 could find no growth stimulation at low concentrations, and described dalapon as an antiauxin from its interference with indole-3-acetic acid effects. The herbicidal properties of trichloroacetate do not depend on its protein-denaturing ability, and those of 2,2-dichloropropionic acid involve, at least indirectly, the synthesis of pantothenic acid. 

Application of ethylene-,4C to plants resulted in only a 2.4% conversion into soluble carbohydrates, 11% into ether-soluble materials, 6.9% into phytol, 31.7% into cellulose and lignin, and 9.6% into soluble protein and non-protein material, mainly phosphates. 9 Treatment of detached fruit (such as apples, bananas, peaches, figs, and pears) with synthetic auxins, especially (2,4,5-trichlorophenoxy) acetic acid, speeded up ripening, as indicated by color, taste, softness, and starch breakdown. 7 Other fruits have been similarly ripened, 8 and the treatments are effective both on climacteric and non-climacteric fruit. 

The shikimate/arogenate pathway leads to the formation of three aromatic amino acids L-phenylalanine, L-tyrosine, and L-tryptophane. This amino acids are precursors of certain homones (auxins) and of several secondary compounds, including phenolics [6,7]. One shikimate/arogenate is thought to be located in chloroplasts in which the aromatic amino acids are produced mainly for protein biosynthesis, whereas the second is probably membrane associated in the cytosol, in which L-phenylalanine is also produced for the formation of the phenylpropanoids [7]. Once L-phenylalanine has been synthesized, the pathway called phenylalanine/hydroxycinnamate begins, this being defined as "general phenylpropanoid metabolism" [7]. 

Napier, R. M., and M. A. Venis, From auxin-binding protein to plant hormone receptor Trends Biochem. Sci. 16 72— 75, 1991. 

Inhibitors of protein synthesis have been shown to block both the rapid and slow auxin-mediated growth responses. How do you explain these observations ... 

On the basis of these observations, it was tentatively concluded (3) that auxin-treated pea tissue elaborates two cellulases which are physically so distinct that it is unlikely that one could have derived from the other. Of course, if two forms of cellulase arise from genetically determined differences in protein structure, it would be legitimate to refer to them as isozymes (21). But in the absence of proof that the pea or any other plant cellulases are under separate genetic control, we will continue to refer to them as multiple forms. 

These observations are consistent with the conclusion that auxin treatment leads to the synthesis of BS cellulase, which then accumulates in smooth ER vesicles. There is direct evidence that the synthesis occurs in rough ER vesicles (11). Cellulase activity was shown (25) to increase in RNA-rich pea microsomes, provided these were isolated from auxin-treated tissue, when the preparations were incubated with ingredients necessary for carrying out protein synthesis in vitro. Messenger RNA (mRNA) from these microsomes has been translated in a different ribo-somal system and shown to synthesize BS cellulase protein (II). Thus, it is legitimate to use the term "induction to apply to the ability of auxin to evoke the appearance of mRNA for BS cellulase. 

Efforts may now have been successful Whereas normal tobacco cells require auxin for division, sequence tagged (TDNA) lines encoding an adenylyl cyclase were obtained which were auxin-independent but cAMP-dependent. From one line (axi 141), a complementary DNA encoding adenylyl cyclase has been isolated with characteristic leucine repeats and similarity to yeast adenylyl cyclase (Ichikawa et al., 1997). The result seems not to be the expression of an alternative division pathway from the normal auxin-driven division since it is blocked by auxin inhibitors and is activated by cAMP and the cyclase activator forskolin. Perhaps a link to G-protein at the membrane will now bring plant growth regulation even closer to that of animals. 

Leyser, O.H.M., Lincoln, C.A., Timpte, C., Lammer, D., Turner, J., Estelle, M. (1993). Arabidopsis auxin-resistance gene AXR1 encodes a protein related to ubiquitin-activating enzyme El. Nature (London) 364, 161-164. 

Napier, R.M. Venis, M.A. (1993). Tansley Review No. 79. Auxin action and auxin binding proteins. New Phytol. 129, 167-201. 

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. 

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