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PubMed1975

Effect of Gibberellic Acid, Kinetin, and Ethylene plus Carbon Dioxide on the Thermodormancy of Lettuce Seed (Lactuca sativa L. cv. Mesa 659).

The effects of gibberellic acid and kinetin with ethylene plus carbon dioxide on the thermodormancy of lettuce seeds (Lactuca sativa L. cv. Mesa 659) at 35 C in the dark were studied. The combination of gibberellic acid plus kinetin with ethylene plus carbon dioxide was most effective in overcoming thermodormancy in these Great Lakes type seeds, alleviating any induced light requirement. Gibberellic acid action required at least a minimal level of ethylene plus carbon dioxide. Kinetin action was independent of ethylene plus carbon dioxide but interacted with the gases when the gases were added. A schematic representation of the interaction is presented.

Journal Article↗
PubMed1976

Rhythmic Nitrate Reductase Activity in Leaves of Capsicum annuum L. and the Influence of Kinetin.

In the expanding leaves of Capsicum annuum L. cv. California Wonder, two of the three peaks of nitrate reductase activity associated with the light period exhibit a circadian rhythm that persists in continuous light.The spray application of kinetin to the whole shoot or to leaves other than the ones used for nitrate reductase assay causes a phase shift in the activity peaks and this has been used in preliminary investigations of the character of the mechanisms controlling the timing of the peaks.There was some indication that the rate of translocation of nitrate from the roots might be involved. The levels of nitrate moving up the stem after kinetin treatment were more dependent upon the rate of sap flow than on the concentration of nitrate in the sap. For this reason, transpiration rates in whole plants were measured after kinetin treatment but no change in pattern was seen that would correlate with the phase shift in nitrate reductase activity.The occurrence of nitrate reductase peaks in excised leaves suggested a leaf-based in addition to a root-or stem-based mechanism in the timing of nitrate reductase activity in the leaves.

Journal Article↗
PubMed1979

Movement of Kinetin and Gibberellic Acid in Leaf Petioles during Water Stress-induced Abscission in Cotton.

Movement of [(14)C]kinetin and [(14)C]gibberellic acid was examined in cotton (Gossypium hirsutum L.) cotyledonary petiole sections independent of label uptake or exit from the tissue. Sections 20 millimeters in length were taken from well watered, stressed, and poststressed plants. Transport capacity was determined using a pulse-chase technique. Movement of both kinetin and gibberellic acid was found to be nonpolar with a velocity of 1 millimeter per hour or less, suggesting passive diffusion. Neither water stress nor anaerobic conditions during transport of labeled material affected the transport capacity of the petioles.Results suggested strong kinetin binding but weak gibberellic acid binding in the tissue sections. Apparent binding of both growth regulators was unaltered by the experimental conditions. Movement of these two growth regulators within cotton cotyledonary petioles plays a minor role in the stress-induced, foliar abscission process.

Journal Article↗
PubMed1980

Biochemical and Cytological Analyses of RNA Synthesis in Kinetin-treated Pea Root Parenchyma.

Excised cortical parenchyma from the pea root (cv. Little Marvel) responds to kinetin/auxin treatment with an increased rate of RNA synthesis well before reinitiating DNA synthesis. Few cells synthesize RNA in the 1st hour of culture. In the presence of kinetin/auxin, the nuclear labeling index increases 2.5-fold as compared to control cultures. The RNA synthesis response has an apparent lag period of 2-4 hours as shown by double label ([(3)H]adenosine/[(14)C]adenosine) experiments. Qualitatively, the RNA synthesized at 4-6 hours sediments between 18S and 5S. The RNA synthesized at 14-16 hours and 24-26 hours is primarily ribosomal RNA when kinetin is present. In the absence of kinetin, no clear pattern of RNA synthesis emerges.The data are interpreted to mean that kinetin treatment elicits RNA synthesis in a small proportion of the population initially and this may involve messenger-like RNA. Later, more cells synthesize RNA and this is primarily rRNA.

Journal Article↗
PubMed1997

Furfural, a precursor of the cytokinin hormone kinetin, and base propenals are formed by hydroxyl radical damage of DNA.

Recently, we have detected kinetin (N6-furfuryladenine), a well known cytokinin plant hormone, in commercially available DNA, in freshly extracted cellular DNA and in plant cell extracts. We had suggested that the furfuryl moiety of kinetin originates from furfural which is one of the primary oxidation products of deoxyribose in DNA. Here we show that the human cell extracts treated with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) give rise to oxime derivatives of various aldehydes present in the cell. Mass spectrometric analysis of silylated oximes showed several mass signals of different species, one of which was identified as furfural. Furthermore, detailed inspection of the mass spectra of DNA showed the mass signals of 165, 180, 189 and 206 m/z which correspond to cytosine-propenal, thymine-propenal, adenine-propenal and guanine-propenal, respectively. The presence of furfural, along with four base-propenals in the cell extract, as the primary oxidation products of deoxyribose, suggests that degradation of sugar residues in DNA is one of the major routes of cellular damage in addition to the modification of nucleic acid bases.

Adenine↗
PubMed1996

Evidence for the presence of kinetin in DNA and cell extracts.

In contrast to the current view that kinetin (N6-furfuryladenine) is an unnatural and synthetic compound, we have detected it in commercially available DNA, in freshly extracted cellular DNA from human cells and in plant cell extracts by two independent methods. First, we discovered that N6-furfuryladenine has electrochemical properties that can be applied for monitoring this modified base by a HPLC/UV/EC method. Second, we have confirmed electrochemical assignments by mass-spectrometric analysis. A pathway of kinetin formation is proposed in which the formation of furfural by oxidative damage of the deoxyribose moiety of DNA is followed by its reaction with adenine residues to form N6-furfuryladenine. Since this modification can lead to mutations, the odd DNA base has to be removed by repair enzymes.

Adenine↗
PubMed1994

Effect of abscisic acid, gibberellic acid, indoleacetic acid, and kinetin on selective ribosomal cistron regulation in quiescent and senescent onion leaf base tissue.

Small pieces of tissue from the basal, equatorial, near-apical, and apical regions of the third turgid onion leaf base were treated (3 and 6 h in the dark) with abscisic acid (ABA), gibberellic acid (GA3), indoleacetic acid (IAA), and kinetin (K) and compared with responses in water controls. ABA inhibited the activation (increase in size and changes in morphologies from round or oval to elongated-oval and dumbbell) of major nucleolar organizer regions (NORs) in basal, equatorial, and near-apical tissue. GA3 and K activated the major NORs in the basal, equatorial, and near-apical tissue. IAA stimulated the activation of major NORs in basal tissue but inhibited their activation in equatorial and near-apical tissue. No major nucleoli were activated in control or plant growth regulator-treated apical tissue. Minor NORs were not expressed in the control and plant growth regulator-treated tissue in these four locations. Actinomycin D and cycloheximide inhibited major NOR activation in equatorial control and kinetin-treated tissue. We propose that ABA, GA3, IAA, and K are major NOR regulators. We infer that the basal through near-apical cells were quiescent during post-harvest storage and that the cells in the apical tissue had senesced beyond the point of no return (degeneration of the karyoskeleton) in the cellular senescence pathway.

Abscisic Acid↗
PubMed1976

Effects of kinetin on phosphorylation of leaf membrane proteins.

Isolated Chinese cabbage leaf membranes were phosphorylated by membrane-associated protein kinase(s) in the presence or [gamma-32P]ATP. Membrane-associated 32P radioactivity appeared to be bound to membrane proteins. Both smooth cell membranes and chloroplast lamellae reacted with ATP. Phosphorylation of the membranes was inhibited by Ca2+ and partially inhibited by kinetin or 6-benzyladenine. The possibility that cytokinin effects on membrane phosphorylation might increase ion availability was investigated in vivo. It was found that Ca2+ could substitute for kinetin in the leaf disc expansion assay.

Cell Membrane↗
PubMed2006

Kinetin--a multiactive molecule.

Cytokinins are important adenine derivatives that serve as hormones to control many processes in plants. They were discovered as factors that promote cell division in tobacco tissue cultures and have been shown also to regulate several other developmental events. Kinetin which was isolated 50 years ago for the first time as a plant hormone, as well as other cytokinins isopentenyladenine, zeatin and benzylaminopurine induce callus (clusters of dedifferentiated plant cells) to redifferentiate into adventitious buds. Because of some similarities in the biological phenotypes of cancer and callus cells, cytokinins and especially kinetin, affect the differentiation of human cells through a common signal transduction system. Therefore, cytokinins found their way to use in molecular medicine.

Cell Differentiation↗
PubMed2006

Structure of N6-furfurylaminopurine (kinetin) dihydrogenphosphate.

The crystal structure of kinetin dihydrogenphosphate has been determined at 115 and 293 K. Kinetin dihydrogenphosphate undergoes a polymorphic phase transition at 291.1 K. In both phases the crystal belongs to the triclinic system with the symmetry described by the space group P\bar 1. In the low-temperature phase, the unit cell is doubled along the a axis. There is a dynamic equilibrium between different tautomeric forms of the adenine residue, determined by the distribution of H atoms within the network of hydrogen bonds.

Crystallography, X-Ray↗
PubMed1960

Effect of kinetin on Paramecium caudatum under varying culture conditions.

When kinetin (1 mg/liter) is added to hay infusion medium, the generation time of Paramecium caudatum is shortened immediately upon transfer of the protozoa from stock to isolation culture. Kinetin is particularly effective when culture conditions are suboptimal, perhaps because it substitutes for or supplies some factor which becomes limiting after transfer.

Kinetin↗
PubMed1964

TOXIC EFFECT OF PSEUDOMONAS TABACI ON RNA METABOLISM IN TOBACCO AND ITS COUNTERACTION BY KINETIN.

Treatment of intact tobacco leaves with toxin-containing culture filtrates of Pseudomonas tabaci markedly reduced the ribonucleic acid content of the leaves. The decrease was counteracted by spraying the leaves with 10(-4)M kinetin. Simultaneously with the decrease in RNA, the ribonuclease activity of extracts from tissues treated with toxin increased. Experiments on the effect of kinetin on the ribonuclease activity of toxin-treated tissues gave no consistent results.

Chemistry Techniques, Analytical↗
PubMed1987

[Kinetin and the germinating capacity of Lupinus multilupa seeds].

The effect of kinetin (10(-6) M and 10(-4) M) on the germinating capacity and incorporation of 8-C14 adenine into DNA, RNA and RNA Poly A+ of embryos and cotyledons from Lupinus multilupa L. seeds have been studied. Kinetin enhanced the germinative capacity of the seeds and the incorporation of 8-C14 adenine into DNA, RNA and Poly A+ of embryos and cotyledons. However, there seems to be no close relationship between the DNA and RNA biosynthesis of embryos and cotyledons and the ability of the seeds to germinate and their embryos to continue growing.

DNA↗
PubMed1968

Effect of second-leaf removal or kinetin treatment on the nucleic acid metabolism of senescing first seedling leaf of barley.

1. Changes in nucleic acid metabolism in first seedling leaves of barley plants during aging (from 7 to 27 days) were followed, and the effect of continual removal of the second leaf and basal meristem or of treating the first leaf with 20p.p.m. kinetin on these changes was examined. During aging of the first seedling leaves the ribosomal RNA, DNA and soluble RNA declined, with ribosomal RNA showing the most rapid fall. This was, however, accompanied by increased incorporation of (32)P into RNA, which reached its peak on the fifteenth day. 2. Second-leaf removal partially suppressed first-leaf senescence as judged by retarded chlorophyll and nucleic acid decline and by a decreased extent of RNA labelling. Treatment with kinetin, however, did not prove effective. 3. No significant differences in the sucrose-gradient pattern of (32)P-labelled nucleic acids or in the (32)P-labelled nucleotide composition of RNA fractions during aging or during the two treatments were noted, except for a decrease in CMP content of soluble RNA during aging. 4. The results demonstrate that important changes in RNA metabolism are associated with leaf senescence.

Aging↗
PubMed1970

The binding of kinetin to plant ribosomes.

The synthetic cytokinins kinetin and 6-benzylaminopurine exhibit equilibrium-type binding to purified chinese-cabbage leaf ribosomes. At 23mum and 4 degrees C one molecule of kinetin and 1.34 molecules of 6-benzylaminopurine are bound per ribosome. Adenine and adenine derivatives that are inactive as cytokinins showed much less affinity for ribosomes. Pretreatment of ribosomes with 0.5m-ammonium chloride or Triton X-100 did not decrease the extent of cytokinin binding. Binding appeared to be to the 83S ribosome species. A positive correlation between the extent of binding and the biological effect of various cytokinin analogues was demonstrated. These results are discussed in terms of cytokinin control of growth processes at the ribosomal level.

Adenine↗
PubMed1974

Polar transport of kinetin in tissues of radish.

Polar transport of kinetin-8-(14)C occurred in segments of petioles, hypocotyls, and roots of radish (Raphanus sativus L.). The polarity was basipetal in petioles and hypocotyls and acropetal in roots. In segments excised from seedlings with fully expanded cotyledons, indole-3-acetic acid was required for polarity to develop. In hypocotyl segments isolated at this stage, basipetal and acropetal movements were equal during the first 12 hours of auxin treatment after which time acropetal movement declined. Pretreatment with auxin eliminated this delay in the appearance of polarity. In hypocotyl segments excised from seedlings with expanding cotyledons, exogenous auxin was unnecessary for polarity. Potassium cyanide abolished polarity at both stages of growth by allowing increased acropetal movement. The rate of accumulation of kinetin in receiver blocks was greater than the in vivo increase in cytokinin content of developing radish roots.

Journal Article↗
PubMed1978

Kinetin Reversal of NaCl Effects.

Leaf discs of Nicotiana rustica L. were floated on NaCl in the presence of kinetin or abscisic acid. On the 5th day (14)CO(2) fixation, [(3)H]leucine incorporation, stomatal conductance, and chlorophyll content were determined. Kinetin either partially or completely reversed the inhibitory effects of NaCl while ABA had no effect.

Journal Article↗