Inhibition of carnation petal inrolling by growth retardants and cytokinins

2000 ◽  
Vol 27 (4) ◽  
pp. 357 ◽  
Author(s):  
Elizabeth A. Taverner ◽  
David S. Letham ◽  
Jian Wang ◽  
Edwina Cornish
Keyword(s):  
Rna Synthesis ◽  
Morphological Changes ◽  
Zeatin Riboside ◽  
Cytokinin Oxidase ◽  
Cut Flowers ◽  
Potential Growth ◽  
Level Of Activity ◽  
Hormonal Interaction ◽  
Exogenous Cytokinin ◽  
Carnation Petals

Excised carnation petals induced to senescence by ethrel (an ethylene-releasing compound) exhibited morphological changes that closely resembled those of senescing petalsin situ in cut flowers. The sensitivity of the excised petals to ethylene was reduced by exogenous cytokinin and this type of hormonal interaction in the control of plant development is discussed. Using the excised petals, a number of known and potential growth inhibitors were compared for ability to prevent petal inrolling induced by ethrel. Cycloheximide and 6-methylpurine were the most effective and inhibited inrolling almost completely, but purine, purine riboside, lauric acid, L-azetidine-2-carboxylic acid and n-decyl alcohol were also very effective. All these compounds were considerably more effective than any cytokinin tested. When supplied through the transpiration stream to short-stemmed carnations, cycloheximide, 6-methylpurine and purine inhibited inrolling nearly completely and the flowers finally senesced by water loss. 6-Methylpurine inhibited ethylene production in cut flowers and RNA synthesis in excised petals very markedly. Degradation of exogenous zeatin riboside by cytokinin oxidase, and the level of activity of the enzyme in petals, were reduced by 6-methylpurine. These biochemical changes probably account for the strong inhibition of inrolling induced by this compound.

scholarly journals Bryostatin 1 induces differentiation of B-chronic lymphocytic leukemia cells

Blood ◽  
1989 ◽  
Vol 74 (5) ◽  
pp. 1747-1757 ◽  
Author(s):  
HG Drexler ◽  
SM Gignac ◽  
RA Jones ◽  
CS Scott ◽  
GR Pettit ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Rna Synthesis ◽  
Morphological Changes ◽  
Marine Invertebrate ◽  
Qualitative Difference ◽  
Calcium Ionophore ◽  
Lymphocytic Leukemia ◽  
Ionophore A23187 ◽  
Bryostatin 1 ◽  
Stimulatory Action

Abstract Peripheral blood cells from nine patients with B-chronic lymphocytic leukemia (B-CLL) were treated in vitro with bryostatin 1 (a macrocyclic lactone derived from a marine invertebrate). Like the phorbol ester 12- 0-tetradecanoyl-phorbol 13-acetate (TPA), bryostatin 1 activates protein kinase C (PKC), which plays a central role in the phosphatidylinositol signal transduction pathway. The effects of bryostatin 1 alone and in combination with TPA or with the calcium mobilizing ionophore A23187 were assessed by morphological appearance, cell adherence and aggregation, RNA and DNA synthesis, and immunoglobulin (Ig) production. While eight of nine B-CLL cultures remained proliferatively inert, bryostatin 1 could effectively trigger activation and differentiation of B-CLL cells in all cases as inferred by the induction of morphological changes, RNA synthesis, and monotypic Ig production. Addition of calcium ionophore A23187 to bryostatin 1- exposed cells resulted in significantly increased values for RNA synthesis and Ig production and in the acquisition of plasmacytoid morphology. Bryostatin 1 and the dual signal of bryostatin 1 plus A23187 mimicked the stimulatory action of TPA and the combination of TPA plus A23187, respectively. Overall, bryostatin 1 was less active than equivalent concentrations of TPA. This lesser efficacy may, however, reflect a quantitative rather than qualitative difference. Bryostatin 1 partially antagonized TPA-mediated effects on B-CLL cells suggesting different modes of action by the two activators. These studies indicate that bryostatin 1 has effective differentiation- inducing properties on B-CLL cells that can differentiation-inducing properties on B-CLL cells that can be accentuated by a calcium ionophore.

scholarly journals SPHEROIDAL AND RING NUCLEOLI IN AMPHIBIAN OOCYTES

1967 ◽  
Vol 35 (2) ◽  
pp. 421-434 ◽  
Author(s):  
Nancy J. Lane
Keyword(s):  
Granular Material ◽  
Rna Synthesis ◽  
Morphological Changes ◽  
Ambystoma Mexicanum ◽  
Entire Length ◽  
Short Term ◽  
Asymmetrical Pattern ◽  
Fibrillar Component

In maturing oocytes of the newt Triturus viridescens, the nucleoli undergo a series of morphological changes that are very similar to those described by Callan for the axolotl, Ambystoma mexicanum. The nucleoli first assume the form of spheroids which then become extended into ring or necklace shapes that are DNase-sensitive; in mature oocytes the nucleoli revert to a spheroidal form. Short term in vitro incorporation studies with uridine-3H on both species show that RNA synthesis occurs in a restricted, eccentric portion of the spheroidal nucleoli, thereby producing an asymmetrical pattern of labeling. In the ring forms, however, the localization of the radioactivity suggests that synthesis takes place symmetrically throughout their entire length. The changes in nucleolar morphology apparently reflect the fact that the component DNA has undergone a redistribution from a localized region in the spheroidal nucleoli to an extended circle in the rings; the patterns of uridine-3H incorporation, therefore, parallel the distribution of DNA in both the spheroidal and the ring nucleoli. Ultrastructurally, the nucleoli contain a fibrillar component that corresponds in position to that of the DNA. The typical spheroidal nucleolus consists of a fibrillar core situated eccentrically and surrounded by a hull of granular, ribonucleoprotein material. The ring nucleoli are composed of a central fibrous region that is ensheathed all around its circumference by a layer of similar granular material. This granular substance is thicker at intervals along the length of the rings, representing the "beads" of the necklaces.

Application of cytokinins to flowers to increase pod set in Lupinus angustifolius L

1993 ◽  
Vol 44 (8) ◽  
pp. 1799 ◽  
Author(s):  
CA Atkins ◽  
A Pigeaire
Keyword(s):  
Reproductive Development ◽  
Zeatin Riboside ◽  
Lupinus Angustifolius ◽  
Open Flower ◽  
Positive Effects ◽  
Stage Of Development ◽  
Flower Abortion ◽  
Whole Plant ◽  
Exogenous Cytokinin ◽  
Flower Stage

Exogenous application of a 2 mol m-3 buffered solution of N6 benzylaminopurine (BAP) to flowers on the main stem inflorescence of Lupinus angustifolius L, cv. Danja profoundly altered reproductive development by reducing post-anthesis abscission of flowers and small pods. The same effect of BAP was recorded for a mutant (abs-) of cv. Danja, in which organ abscission was completely absent, indicating that localized application of cytokinin enhanced reproductive development rather than reduced pedicel abscission per se in the parent line. Application to pedicel and sepals at the open flower stage completely eliminated flower abortion on the main inflorescence, compared with less than 50% pod initiation on untreated inflorescences, more than doubled final pod yield on the main inflorescence and increased the number of mature pods on the whole plant by 33%. A single dose of BAP, to an inflorescence which bore flowers ranging in their stage of development from post-anthesis to immature flower buds, significantly increased the number of pods initiated and at final harvest, measured on a per plant basis. A number of synthetic and naturally occurring cytokinins, including zeatin riboside and dihydrozeatin riboside, were also effective. BAP application induced a longer period of flowering and resulted in a considerably thickened raceme. This was most marked at the distal end which showed enhanced cambial development and secondary vascularization compared with untreated controls. The positive effects of BAP application on pod initiation were not restricted to cv. Danja but were found also for cv. Warrah and cv. Gungurru, both of which have enhanced pod set compared with Danja. Enhanced pod initiation on the main inflorescence generally reduced the number of pods developing on branch inflorescences. Additional application of BAP to flowers on branches, even at the most opportune time and at the most effective site, did not enhance pod initiation and, in some cases, significantly reduced pod set on these branches. The data indicate that it would be very difficult to exploit the positive effect of exogenous cytokinin application on pod set in field crops of lupin. However, selection or genetic engineering of plants with higher levels of endogenous cytokinins in flowers or flower parts at anthesis may provide a means by which to assess the importance of this factor in determining yield stability.

Cytokinins in Plant Pathogenic Bacteria and Developing Cereal Grains

1993 ◽  
Vol 20 (5) ◽  
pp. 621 ◽  
Author(s):  
RO Morris ◽  
DG Blevins ◽  
JT Dietrich ◽  
RC Durley ◽  
SB Gelvin ◽  
...  
Keyword(s):  
Cell Division ◽  
High Performance ◽  
Pathogenic Bacteria ◽  
Specific Activity ◽  
Zeatin Riboside ◽  
Cytokinin Oxidase ◽  
Endosperm Cell ◽  
Cytokinin Biosynthesis ◽  
Cereal Grain ◽  
Major Route

Cytokinin analysis by immunoaffinity chromatography (IAC), high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA) or enzyme-linked immunosorption assay (ELISA) has been used to study two separate topics: the role of tRNA in bacterial cytokinin biosynthesis and the changes in cytokinin concentration which occur during cereal grain development. Transfer RNA isopentenylation in the gall-forming plant pathogen Agrobacterium tumefaciens is encoded by the chromosomal miaA locus. Mutation of miaA reduces tRNA isopentenylation significantly and preliminary data suggest that turnover of isopentenylated tRNA is responsible for low level secretion of free N6-isopentenyladenine (iP) by the bacteria. However, the major route of cytokinin biosynthesis by gall-forming plant patho- genic bacteria is not via tRNA turnover but by direct biosynthesis mediated by dimethylallylpyro- phosphate: 5'-AMP transferase (DMAPP :AMP transferase) encoded by such genes as ipt, tzs (from A, tumefaciens) or ptz (from Pseudomonas savastanoi). Analysis of cytokinin levels in developing wheat and rice grains in the period immediately following pollination showed large transient increases in zeatin (Z) and zeatin riboside (ZR) which coincided with the period of maximum endosperm cell division reported by others. Detailed analyses of maize kernels, where development can be staged readily, showed that Z and ZR concentrations peaked 9 days after pollination (DAP). During the period 8-10 DAP, cytokinin oxidase underwent a significant increase in specific activity, indicating that cytokinin catabolism was enhanced as endosperm cell division ended.

scholarly journals Identification and Functional Characterization of Apple MdCKX5.2 in Root Development and Abiotic Stress Tolerance

Horticulturae ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 62
Author(s):  
Yang Liu ◽  
Xun Wang ◽  
Xiaofei Wang ◽  
Wensheng Gao ◽  
Chunxiang You
Keyword(s):  
Expression Analysis ◽  
Root Development ◽  
Expression Profiles ◽  
Abiotic Stress Tolerance ◽  
Expression Patterns ◽  
Functional Characterization ◽  
Primary Root ◽  
Cytokinin Oxidase ◽  
Lateral Root Development ◽  
Exogenous Cytokinin

Cytokinin oxidase/dehydrogenases (CKXs) are the key enzymes in cytokinin degradation and have been widely studied in model plants. Little is known about apple’s (Malus×domestica) CKX genes. Here, using genome-wide analysis, we identified 10 MdCKX genes in apple. The phylogenetics, chromosome locations, and genome structures were then tested. Expression analysis showed that MdCKX genes had different expression profiles in apple, pointing to the different roles. Meanwhile, relative expression analysis showed that these genes have different expression patterns in response to several exogenous cytokinin factors, including trans-zeatin (ZT), thidiazuron (TDZ), and N6-furfuryladenine (KT). Finally, we introduced the MdCKX5.2 gene into Arabidopsis to evaluate its functions, and the results suggested the transgenic Arabidopsis displayed phenotypes related to promoting primary root and lateral root development, response to exogenous ZT, and conferring to drought and salt tolerant. Taken together, our results provide insights on the possible application of the MdCKX5.2 gene for molecular breeding in apples.

scholarly journals NUCLEOLAR AND BIOCHEMICAL CHANGES DURING UNBALANCED GROWTH OF TETRAHYMENA PYRIFORMIS

1965 ◽  
Vol 26 (3) ◽  
pp. 845-855 ◽  
Author(s):  
Ivan L. Cameron ◽  
E. Ernest Guile
Keyword(s):  
Protein Synthesis ◽  
Stationary Phase ◽  
Rna Synthesis ◽  
Morphological Changes ◽  
Synthetic Medium ◽  
Tetrahymena Pyriformis ◽  
Lag Phase ◽  
Proteose Peptone ◽  
Rna And Protein Synthesis ◽  
Peptone Medium

Numerous nucleoli can be observed in the macronucleus of the logarithmically growing ciliated protozoan Tetrahymena pyriformis; at late log phase the nucleoli aggregate and fuse. In stationary phase this fusion process continues, leaving a very few large vacuolated nuclear fusion bodies in the nucleus. When these stationary phase cells are placed into fresh enriched proteose peptone medium, the large fusion bodies begin to disaggregate during the 2.5-hour lag phase before cell division is initiated. By 3 to 6 hours after inoculation the appearance of the nucleoli in many cells returns to what it was in logarithmic cells. In view of the possible role of nucleoli in ribosome synthesis, attempts were made to correlate the morphological changes to changes in RNA and protein metabolism. The beginning of an increased RNA synthesis was concomitant with the beginning of disaggregation of the large fusion bodies into nucleoli, which was noticed in some cells by 1 hour after the return to fresh enriched proteose peptone medium. Increased protein synthesis then followed the increased RNA synthesis by 1 hour. The supply of RNA precursors (essential pyrimidines) were removed from cultures which were grown on a chemically defined synthetic medium, in order to study the relation between nucleolar fusion and synthesis of RNA and protein. Pyrimidine deprivation drastically curtailed RNA and protein synthesis, but did not cause fusion of nucleoli. When pyrimidines were added back to this culture medium, RNA synthesis was immediately stimulated and again preceded an increased protein synthesis by 1 hour. These studies suggest the involvement of unfused nucleoli in RNA and protein synthesis and demonstrate the extreme plasticity of nucleoli with respect to changes in their environment.

scholarly journals SYNTHESIS OF MESSENGER-LIKE RIBONUCLEIC ACID AND PROTEIN DURING MEIOSIS IN ISOLATED CELLS OF TRILLIUM ERECTUM

1963 ◽  
Vol 19 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Yasuo Hotta ◽  
Herbert Stern
Keyword(s):  
Messenger Rna ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Morphological Changes ◽  
Reaction Rates ◽  
Meiotic Stage ◽  
Isolated Cells ◽  
Rna Analysis ◽  
Protein And Rna Synthesis

The synthesis of RNA and protein by cultures of isolated microsporocytes has been demonstrated. The variation in capacities of such cultures to perform syntheses is a function of meiotic stage and parallels the pattern of changes observed for microsporocytes in situ. A principal feature of this pattern is the induction of syntheses during pachytene and diplotene, stages at which the chromosomes are partly contracted. By use of Actinomycin D, chloramphenicol, pulse-labeling with P32-phosphate, and nucleotide analyses of RNA digests, part of the RNA synthesized has been shown to correspond to messenger RNA. Analysis of reaction rates and the overlappings of protein and RNA synthesis indicates that the spread of cytological events in Trillium is not purely a function of the low temperature at which it occurs but, presumably, arises from a complement of regulatory devices which govern the periodic onset of reactions within the cells. The main conclusion drawn from the whole of these studies is that the sequence of morphological changes associated with chromosome contraction and movement during meiosis is accompanied by a set of gene transcriptions. Although comparatively few genes are presumed to be active during meiosis, the action of such genes may be essential to a translation of some of the information embodying the meiotic sequence which has been stored in the genome in the course of evolution.

CONTROL OF RNA SYNTHESIS IN YEAST

1974 ◽  
Vol 16 (4) ◽  
pp. 751-764
Author(s):  
H. O. Halvorson ◽  
D. Kaback ◽  
S. Sogin ◽  
E. M. Sajdel-Sulkowska ◽  
I. Takano
Keyword(s):  
Cell Cycle ◽  
Rna Synthesis ◽  
Rrna Synthesis ◽  
Mrna Synthesis ◽  
Continuous Increase ◽  
Level Of Activity ◽  
Physiological Properties ◽  
Polymerase I ◽  
Chromosome I ◽  
Definite Period

During the cell cycle in Saccharomyces cerevisiae there is an ordered appearance of a number of enzymes and various physiological properties but a continuous increase in the rate of rRNA synthesis. A detailed study of rRNA synthesis has shown that there are reiterated genes for rRNA which are largely clustered on chromosome I and appear to be transcribed continuously during the cell cycle. However, the level of activity of polymerase I is proportional to the level of rRNA during the cell cycle and is correlated with the growth rate of the culture. In contrast, the level of polymerase II, thought to be involved in mRNA synthesis, increases during a definite period of the cell cycle characteristic of step enzymes in yeast. It would appear that the level of the activity of polymerase I is involved in the regulation of rRNA synthesis. Possible other mechanisms for the regulation of rRNA are discussed.

Mild temperature stress modulates cytokinin content and cytokinin oxidase/dehydrogenase activity in young pea plants

2009 ◽  
Vol 57 (1) ◽  
pp. 33-40 ◽  
Author(s):  
I. Vaseva ◽  
D. Todorova ◽  
J. Malbeck ◽  
A. Travničkova ◽  
I. Machačkova
Keyword(s):  
Low Temperature ◽  
Enzymatic Activity ◽  
Dehydrogenase Activity ◽  
Growth Conditions ◽  
Zeatin Riboside ◽  
Cytokinin Oxidase ◽  
Temperature Stresses ◽  
Isopentenyl Adenine ◽  
Mild Temperature ◽  
Adaptive Reactions

Cytokinin oxidase/dehydrogenase (CKX: EC 1.5.99.12) is able to provide a means for the rapid turnover of its substrate and it has been considered responsible for changes in the cytokinin pool in an adverse environment. Mild temperature stresses (10°C and 33°C average) were applied to young pea plants of two varieties (cvs. Manuela and Scinado) in order to assess the response of the cytokinin pool and CKX activity to altered growth conditions. Both temperature treatments increased the isopentenyl adenine (iP) and isopentenyl adenine riboside (iPR) contents in stressed plants. This trend was far more pronounced in the leaves. Low temperature additionally resulted in elevated cis zeatin riboside ( cis ZR) and CKX activity. Heat did not influence the enzymatic activity in the leaves, while opposing trends were observed in the root-derived CKX activity of the two tested varieties. The data suggest that variance in the temperature provokes adaptive reactions in the cytokinin pool, which is maintained by CKX activity.

scholarly journals Bryostatin 1 induces differentiation of B-chronic lymphocytic leukemia cells

Blood ◽  
1989 ◽  
Vol 74 (5) ◽  
pp. 1747-1757 ◽  
Author(s):  
HG Drexler ◽  
SM Gignac ◽  
RA Jones ◽  
CS Scott ◽  
GR Pettit ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Rna Synthesis ◽  
Morphological Changes ◽  
Marine Invertebrate ◽  
Qualitative Difference ◽  
Calcium Ionophore ◽  
Lymphocytic Leukemia ◽  
Ionophore A23187 ◽  
Bryostatin 1 ◽  
Stimulatory Action

Peripheral blood cells from nine patients with B-chronic lymphocytic leukemia (B-CLL) were treated in vitro with bryostatin 1 (a macrocyclic lactone derived from a marine invertebrate). Like the phorbol ester 12- 0-tetradecanoyl-phorbol 13-acetate (TPA), bryostatin 1 activates protein kinase C (PKC), which plays a central role in the phosphatidylinositol signal transduction pathway. The effects of bryostatin 1 alone and in combination with TPA or with the calcium mobilizing ionophore A23187 were assessed by morphological appearance, cell adherence and aggregation, RNA and DNA synthesis, and immunoglobulin (Ig) production. While eight of nine B-CLL cultures remained proliferatively inert, bryostatin 1 could effectively trigger activation and differentiation of B-CLL cells in all cases as inferred by the induction of morphological changes, RNA synthesis, and monotypic Ig production. Addition of calcium ionophore A23187 to bryostatin 1- exposed cells resulted in significantly increased values for RNA synthesis and Ig production and in the acquisition of plasmacytoid morphology. Bryostatin 1 and the dual signal of bryostatin 1 plus A23187 mimicked the stimulatory action of TPA and the combination of TPA plus A23187, respectively. Overall, bryostatin 1 was less active than equivalent concentrations of TPA. This lesser efficacy may, however, reflect a quantitative rather than qualitative difference. Bryostatin 1 partially antagonized TPA-mediated effects on B-CLL cells suggesting different modes of action by the two activators. These studies indicate that bryostatin 1 has effective differentiation- inducing properties on B-CLL cells that can differentiation-inducing properties on B-CLL cells that can be accentuated by a calcium ionophore.

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