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At least 199 records · Page 11Linked to original sources
PubMed2001

Cellular localization of the signaling components of Arabidopsis His-to-Asp phosphorelay.

In the higher plant, Arabidopsis thaliana, histidine-to-aspartate (His-to-Asp) phosphorelay signal transduction systems play crucial roles in propagation of environmental stimuli, including plant hormones. This plant has 11 sensor His-kinases, 5 histidine-containing phosphotransfer (HPt) factors (AHPs), and 20 response regulators (ARRs). To gain new insight into the functions of these phosphorelay components, their intracellular localization was examined with use of GFP-fusion proteins, constructed for certain representatives of HPt factors (AHP2) and type-A and type-B ARRs (ARR6/ARR7 and ARR10, respectively). The results showed that AHP2 is mainly located in the cytoplasmic space, while both the types of ARRs have an ability to enter preferentially into the nuclei, if not exclusively. Together with the results from an in vitro phosphorelay assay with AHP2 and ARRs, these results are discussed, in terms of a geneal framework of the Arabidopsis His-to-Asp phosphorelay network.

Arabidopsis↗
PubMed1980

Gibberellic acid, a plant growth hormone, enhances mammalian guanylate cyclase activity.

In vivo injections of gibberellic acid, a potent plant growth hormone, are known to increase the growth of animals as well as plants. Investigation into gibberellic acid's growth promoting mechanism in animals at the cellular level focused on guanylate cyclase (E.C.4.6.1.2.), an enzyme known to be associated with growth. Gibberellic acid enhanced the activity of rat lung guanylate cyclase over a concentration range of .00001 mM to 1 mM with no stimulation being observed at .000001 mM. Varying the concentration of the guanylate cyclase co-factor manganese had no effect on gibberellic acid's enhancement of guanylate cyclase activity. Since human and rat growth hormones also enhance guanylate cyclase activity, it appears that at cellular level the mechanism of action of growth promoting hormones may include a common process that involves enhancement of guanylate cyclase activity.

Animals↗
PubMed2000

[Separation and determination of three plant internal hormones by gas chromatography].

A method for the simultaneous separation and determination of three plant internal hormones indole acetic acid (IAA), abscisic acid(ABA) and gibberellic acid(GA) in plant by gas chromatography with wide-bore capillary column is described. The gas chromatographic conditions were as follows: FID detector; HP-1 capillary column, 5 m x 0.53 mm x 2.65 microns film; the column temperature, 220 degrees C; the injector temperature, 250 degrees C; the detector temperature, 280 degrees C, carrier gas, 3.5 mL/min N2; internal standard n-docosane. All components and internal standard were separated in 8 min. The detection limit of IAA, ABA and GA were 0.16, 0.08 and 0.48 mg/L respectively. The relative standard deviations were 2.2%, 1.7% and 2.8% respectively. The linear range were 0.16-80 mg/L(r = 0.9986), 0.08-40 mg/L (r = 0.9993) and 0.48-240 mg/L (r = 0.9991) respectively. The average recoveries were (88.4 +/- 2.4%)%, (92.2 +/- 1.2)% and (91.8 +/- 1.8)% respectively. The method is simple, rapid, sensitive and reproducible.

English Abstract↗
PubMed1995

Plant growth hormone kinetin delays ageing, prolongs the lifespan and slows down development of the fruitfly Zaprionus paravittiger.

A cytokinin plant growth hormone kinetin (Kn) retards senescence in plants and delays ageing in human cells in culture. We have now observed that Kn also slows down ageing and prolongs the lifespan of the fruitfly Zaprionus paravittiger when these insects are fed with 25-125 ppm Kn added in their diet medium. In addition, 25 ppm Kn also slows down the larval and the pupal stages of the developing insects. However, the anti-ageing effects of Kn are not merely due to the slowing-down of development, but are mainly due to a reduction in the age-specific death rates throughout the adult lifespan.

Adenine↗
PubMed1989

Cloning the mRNA encoding 1-aminocyclopropane-1-carboxylate synthase, the key enzyme for ethylene biosynthesis in plants.

Ethylene is the plant hormone that controls several features of plant growth and development. The rate-limiting step in its synthesis is the formation of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) from S-adenosylmethionine (AdoMet), catalyzed by ACC synthase. We have isolated a complementary DNA sequence encoding ACC synthase from zucchini (Cucurbita) fruits. The biological activity of the clone was confirmed by the ability of the cloned sequence to direct ACC synthase activity in Escherichia coli and yeast. In vivo studies using the ACC cDNA as probe showed that the ACC synthase gene is induced by a diverse group of inducers, including wounding, Li+ ions, and the plant hormone auxin.

Cloning, Molecular↗
PubMed1999

Carbohydrate binding, quaternary structure and a novel hydrophobic binding site in two legume lectin oligomers from Dolichos biflorus.

The seed lectin (DBL) from the leguminous plant Dolichos biflorus has a unique specificity among the members of the legume lectin family because of its high preference for GalNAc over Gal. In addition, precipitation of blood group A+H substance by DBL is slightly better inhibited by a blood group A trisaccharide (GalNAc(alpha1-3)[Fuc(alpha1-2)]Gal) containing pentasaccharide, and about 40 times better by the Forssman disaccharide (GalNAc(alpha1-3)GalNAc) than by GalNAc. We report the crystal structures of the DBL-blood group A trisaccharide complex and the DBL-Forssman disaccharide complex.A comparison with the binding sites of Gal-binding legume lectins indicates that the low affinity of DBL for Gal is due to the substitution of a conserved aromatic residue by an aliphatic residue (Leu127). Binding studies with a Leu127Phe mutant corroborate these conclusions. DBL has a higher affinity for GalNAc because the N-acetyl group compensates for the loss of aromatic stacking in DBL by making a hydrogen bond with the backbone amide group of Gly103 and a hydrophobic contact with the side-chains of Trp132 and Tyr104. Some legume lectins possess a hydrophobic binding site that binds adenine and adenine-derived plant hormones, i.e. cytokinins. The exact function of this binding site is unknown, but adenine/cytokinin-binding legume lectins might be involved in storage of plant hormones or plant growth regulation. The structures of DBL in complex with adenine and of the dimeric stem and leaf lectin (DB58) from the same plant provide the first structural data on these binding sites. Both oligomers possess an unusual architecture, featuring an alpha-helix sandwiched between two monomers. In both oligomers, this alpha-helix is directly involved in the formation of the hydrophobic binding site. DB58 adopts a novel quaternary structure, related to the quaternary structure of the DBL heterotetramer, and brings the number of know legume lectin dimer types to four.

ABO Blood-Group System↗
PubMed1997

The hormone-responsive NADH oxidase of the plant plasma membrane has properties of a NADH:protein disulfide reductase.

Plasma membranes of plant cells are characterized by a plant hormone (auxin)-responsive oxidation of NADH. The latter proceeds under argon. Also, when NADH oxidation is stimulated 50% by auxin addition, oxygen consumption is reduced by 40%. These findings are reconciled by direct assays using 5,5'-dithiobis-(2nitrobenzoic acid) (DTNB) (Ellman's reagent) that show protein disulfides to be electron acceptors for auxin-stimulated NADH oxidation. In the presence of an external reducing agent such as NADH, cysteine, or dithiothreitol, protein disulfides of the membrane are reduced with a concomitant stoichiometric increase in free thiols. In the absence of an external reducing agent, or in the presence of oxidized glutathione, DTNB-reactive thiols of the plasma membrane are decreased in the presence of auxins. Several auxin-reductant combinations were effective, but the same reductants plus chemically related and growth-inactive auxin analogs were not. A cell surface location of the affected thiols demonstrated with detergents and impermeant thiol reagents suggests that the protein may have a different physiological role than oxidation of NADH. For example, it may carry out some other role more closely related to the function of the auxin hormones in cell enlargement such as protein disulfide-thiol interchange.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2003

Effects of ethylene and abscisic acid upon heterophylly in Ludwigia arcuata (Onagraceae).

In this study, we examined the effects of ethylene and abscisic acid (ABA) upon heterophyllous leaf formation of Ludwigia arcuata Walt. Treatment with ethylene gas resulted in the formation of submerged-type leaves on terrestrial shoots of L. arcuata, while treatments with ABA induced the formation of terrestrial-type leaves on submerged shoots. Measurement of the endogenous ethylene concentration of submerged shoots showed that it was higher than that of terrestrial ones. In contrast, the endogenous ABA concentration of terrestrial shoots was higher than that of submerged ones. To clarify interactions of ethylene and ABA, simultaneous additions of these two plant hormones were examined. When L. arcuata plants were treated with these two plant hormones, the effects of ABA dominated that of ethylene, resulting in the formation of terrestrial-type leaves. This suggests that ABA may be located downstream of ethylene in signal transduction chains for forming heterophyllous changes. Further, ethylene treatment induced the reduction of endogenous levels of ABA in tissues of L. arcuata, resulting in the formation of submerged-type leaves. Thus the effects of ethylene and ABA upon heterophyllous leaf formation are discussed in relationship to the cross-talk between signaling pathways of ethylene and ABA.

Abscisic Acid↗
PubMed2003

CYP72B1 inactivates brassinosteroid hormones: an intersection between photomorphogenesis and plant steroid signal transduction.

Active brassinosteroids, such as brassinolide (BL) and castasterone, are growth promoting plant hormones. An Arabidopsis cytochrome p450 monooxygenase encoded by CYP72B1 has been implicated in brassinosteroid catabolism as well as photomorphogenesis. We expressed CYP72B1 in yeast, coupled with brassinosteroid feeding, and established the biochemical function to be the hydroxylation of BL and castasterone, to give 26-hydroxybrassinolide and 26-hydroxycastasterone, respectively. Brassinosteroid feeding experiments with wild-type Arabidopsis, a CYP72B1 null mutant, and a CYP72B1 overexpression line demonstrated that carbon 26 hydroxylation of active brassinosteroids is an endogenous function of CYP72B1. Seedling growth assays demonstrated that 26-hydroxybrassinolide is an inactive brassinosteroid. Genetic and physiological analysis of the hypocotyl response to exogenous BL and varying intensities of white and monochromatic light suggested that CYP72B1 modulates photomorphogenesis primarily through far-red light and to a lesser extent through blue- and red-light pathways. CYP72B1 transcript accumulation in dark-grown seedlings was organ specific and down-regulated after 1 h of illumination in dim white, red, and blue light, but not far-red light. CYP72B1 translational fusions with the beta-glucuronidase reporter gene demonstrated that protein levels increased in the hypocotyl elongation zone when shifted from the dark to far-red light, but not blue or red light. We propose a model in which Arabidopsis seedling development switches from dark-grown development (skotomorphogenesis) to light-grown development (photomorphogenesis) in part by rapid modulation of brassinosteroid sensitivity and levels. CYP72B1 provides an intersection between the light and brassinosteroid pathways mainly by far-red-light-dependent modulation of brassinosteroid levels.

Arabidopsis↗
PubMed1967

Role of enzymatic wall-softening in plant morphogenesis: hormonal induction in Achlya.

Sexual hormone A, which induces antheridial branching in male strains of Achlya, also elicits a rise in cellulase. The peak of induced cellulase corresponds in time with the appearance of branches that are the male sexual organ primordia; only those strains that branch in response to the hormone show a concomitant rise in cellulase. The response to the hormone is inhibited by compounds that block protein synthesis, for example, p-fluorophenylalanine and puronmycin. Vegetative branching, induced by substrates such as casein hydrolysate, is also accompanied by a rise in cellulase.

Enzyme Induction↗
PubMed1990

Gibberellin perception in the Avena fatua aleurone.

Gibberellins (GAs) are a class of plant hormones involved in the regulation of plant growth and development. A useful model system for studying GA-action is the aleurone layer of cereal grain. In aleurone, GA induces a considerable increase in the rates of transcription of alpha-amylase genes, and this effect can be inhibited by another plant hormone abscisic acid. We anticipate that perception of GA by aleurone cells involves an interaction between the ligand and specific receptors and that this event leads to the observed stimulation in transcription of alpha-amylase, and probably other, aleurone genes. Hormone binding assays with aleurone have not revealed a candidate receptor, and the only aspect of signal transduction that is becoming understood is the likely interaction between specific trans-acting factors and cis-elements in the GA-regulation of alpha-amylase gene transcription. This paper describes the development of novel ways for identifying GA-receptors in aleurone protoplasts of Avena fatua that are based on the use of affinity and antibody probes in functional in vivo assays for GA-receptors. The implications of our current findings are discussed in relation to models of GA-action in aleurone.

Edible Grain↗
PubMed1992

Gibberellin perception and the Avena fatua aleurone: do our molecular keys fit the correct locks?

The plant hormones GA, ABA, and auxin differ from the majority of animal hormones in that they are hydrophobic weak acids. They are soluble in the inter- and intra-cellular environments of plant tissues and their neutral species can cross the plasma membrane by passive diffusion. Auxin transport is mediated by specific uptake and efflux carriers in plasma membranes, and there is some evidence for carrier-mediated uptake of GA and ABA. Because these plant hormones can cross the plasma membrane it is not a prerequisite that receptors for them should be at the protoplast surface. Nevertheless, there is substantial evidence that auxin acts at the plasma membrane, and evidence suggesting that GA may be perceived at the plasma membrane of A. fatua aleurone protoplasts has been reviewed here. It is conceivable that the plant plasma membrane might provide the means to integrate, transduce, and amplify these signals, and that such properties of the plasma membrane, rather than the permeability characteristics of these ligands, may determine the site of perception. Further progress in our understanding of signal transduction pathways that may be involved in the actions of plant hormones is likely to shed light on these questions. It has been proposed that GA receptors involved in cell elongation may be soluble rather than membrane bound. The soluble 50 kDa GA-binding protein observed in aleurone by GA4 photoaffinity labelling may be a good candidate for a soluble GA receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Anti-Idiotypic↗
PubMed2003

Plant Biology. Hormones and the green revolution.

The success of the green revolution largely resulted from the creation of dwarf cultivars of wheat and rice, which had much higher yields than conventional crops. Characterization of these dwarf cultivars showed that the mutant genes were involved in either the synthesis or signaling of gibberellin, a plant growth hormone. In his Perspective, Salamini highlights new work (Multani et al.) that identifies the cause of dwarfism in agronomically important varieties of maize and sorghum. In these cases, dwarfism is caused by defective transport of another growth hormone called auxin.

ATP Binding Cassette Transporter, Subfamily B↗