Plant cytokinins

BAP)] (purine) Ca2+ influx (moss) (at 1 nM) [plant cytokinin -antisenescent, growth regulator, mitogenic]... 

Similar reactions of halogenopurines occur with primary and secondary amines and large numbers of compounds have been made in this way, including several naturally occurring substances many of which are 6-alkylaminopurines including the plant cytokinin zeatin (66JCS(C)92l) (Section 4.09.8.2). For more information see (B-71MI40901). 

Two compounds common in plant metabolism are believed to be precursors of isoprenoid cytokinins in plants adenosine-5 -monophosphate (AMP) and A -isopentenylpyrophos-phate (iPP). As a final product of the mevalonate pathway, the latter substance serves also as a precursor for a wide spectrum of metabolites including some other plant hormones, as abscisic acid, gibberellins and brassinosteroids. The hypothetical scheme of reactions resulting in the formation of iPA, Z and DHZ is given in Fig. 2. The enzyme of entry into isoprenoid cytokinin formation is A -isopentenylpyrophosphate 5 -AMP-A -iso-pentenyltransferase (EC 2.5.1.8, trivially named cytokinin synthetase ). This enzyme activity was first detected in a cell-free preparation from the slime mould Dictyostelium discoideum [7,8]. Later the enzyme from higher plants (cytokinin-independent tobacco callus [9,10] and immature Zea mays kernels [11]) was described and the data were recently summarised in [12], The enzyme is very specific as far as the substrate is concerned [13,14] only the nucleotide AMP can be converted and only iPP (with a double bond in A position) may function as a side chain donor. 

When dealing with transgenic plants one should take into account the potential existence of a plant cytokinin-biosynthetic pathway different from the bacterial ipt encoded pathway. This hypothetical pathway may participate in the accumulation of cytokinins in transformed plants however, this is generally ignored. 

Figueira and Ribeiro (23) used silica gel separations of noncyclic radioactive [H ] adenosine as neuromodulators, and reduced from 2-D to 1-D. The solvents were varieties of butanol-ammonia-water-acetic acid. Rapidity of separation occurred in 3-4 h. Typical separations unequivocally demonstrated cAMP, inosine, adenosine, and adenine. UV sensitivity occurred at S nmol. Paces and Kaminek (24) separated plant cytokinins (adenine) on silica gel in ethanol-ammonium borate butanol-ammonia butanol-water. Norman et al. (25) measured ATP from degraded meat via 5% cold PCA on silica gel and isobutanol-amyl alcohol-ethoxyethanol-ammonia-water. 

Vermeulen, K., Stmad, M., Krystof, V., Havlicek, L., Van der Aa, A., Lenjou, M.,. . . Van Onckelen, H. (2002). Antiproliferative effect of plant cytokinin analogues with an inhibitory activity on cyclin-dependent kinases. Leukemia, 16(3), 299-305. 

Itai, C. Vaadia, Y. (1971). Cytokinin activity in water-stressed shoots. Plant Physiology, 47, 87-90. 

Micellaneous Vitamins, plant growth regulators (auxin.s, cytokinins, gib-berellins), alkyl sulfides, ethanol, H. K nitrate, phosphate, HCO,... 

Frugis, G., Giannino, D., Mele, G., Nicolodi, C., Innocenti, A.M., Chiappetta, A., Bitonti, M.B., Dewitte, W., van Onckelen, H. and Mariotti, D. (1999) Are homeobox knotted-like genes and cytokinins the leaf architects Plant Physiology 119, 371—374. 

There are no new messengers which act as cell-membrane transmitters in plants except cytokinins calcium is more widely used than in unicellular organisms but much less so than in animals. Plants respond to light via phosphorylation and changes from dormancy requires die change of cell calcium. Response times >1 s. There are several other sensors which are sometimes described as hormones, e.g. glucose and NO. 

Next to the amount of P, the chemical form of this nutrient (Lambers et al. 2002 Shu et al. 2005 Shane et al. 2008) and the availability of other nutrients, especially nitrogen, potassium, and iron (Shane and Lambers 2005) affects the formation of cluster roots. It seems to be regulated by several plant hormones. Thus, application of auxin led to the production of cluster roots in white lupin at P concentrations that normally suppress cluster roots (Gilbert etal. 2000 Neumann et al. 2000). Cytokinines might also play a role, as kinetin applied to the growth medium of P-deficient white lupin inhibited the formation of cluster roots (Neumann et al. 2000). 

Zearalenone was also found to be more effective than cytokinin treatment in inducing shoots in in vitro winter wheat production. Moreover, both zearalenone and cytokinins increased the activity of antioxidant enzymes in wheat callus undergoing regeneration, and it is very likely that they also stimulated the plant regeneration process (Szechynska-Hebda et al. 2007). The effectiveness of regeneration on media containing zearalenone shows the possibility of using zearalenone as an alternative hormone also to cytokinins in winter wheat callus culture. 

Plant growth regulators, 13 21-60, 284 carvone, 13 28 cytokinins, 13 28-30 ft-decanol, 13 30 dikegulac, 13 30 ethylene, 13 30-32 gamma aminobutyric acid, 13 32 gibberehins, 13 32-35 indole 3-butyric acid, 13 35-36 lactic acid, 13 36 natural product derivatives,... 

Isolated from plants Lupinic acid - metabolite of the 13 cytokinin zeatin... 

Most species of angiosperms produce hermaphroditic flowers. The unisexuality in some plants most often results from developmentally programmed abortion or selective reduction in sex organ primordia. In dicots, higher levels of auxins, cytokinins, and ethylene usually correlate with female sex expression and in most of them the femaleness is mainly promoted by ethylene. ... 

Miura and co-workers 121) have successfully induced multiple shoot cultures of C. roseus from seedlings in the presence of 1.0 mg/liter of the cytokinin benzyladenine. Vindoline (3) and catharanthine (4) were predominating alkaloids in the MSC-B-1 line, showing levels of 1.8 and 0.37 mg/g dry weight, respectively in the leaf tissue. In the case of catharanthine (4) this represented a 10-fold increase over the parent plant tissue, and such levels were sustained in the regenerated plants. When the benzyladenine was eliminated, overall growth was reduced, but vindoline (3) and catharanthine (4) concentrations increased to 3.2 and 1.1 mg/g dry weight, respectively. 

Isoprenoids that have hormonal and signaling functions form an important group. These include steroid hormones (1 = 6) and retinoate (the anion of retinoic acid 1 = 3) in vertebrates, and juvenile hormone (1 =3) in arthropods. Some plant hormones also belong to the isoprenoids—e.g., the cytokinins, absci-sic acid, and brassinosteroids. 

After preliminary work-up, cytokinins in plant extracts were resolved on RP-8 (520). Other investigators have reported a two-step separation exclusively done on reverse phase to isolate the two nugor cytoUnins of sorghum leaf (52/). 

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