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At least 541 records · Page 30Linked to original sources
PubMed1995

A rice membrane calcium-dependent protein kinase is induced by gibberellin.

A rice (Oryza sativa) seed plasma-membrane calcium-dependent serine/threonine protein kinase (CDPK) has been partially purified. Comparing results in seeds that were treated with and without the plant hormone gibberellin (GA) for 10 min showed that rice CDPK was highly induced by GA. After separating solubilized membrane proteins by sodium dodecyl sulfate-gel electrophoresis, followed by renaturation, a radiolabeled phosphoprotein band of approximately 58 kD was detected, and it was apparently produced by autophosphorylation. There are five aspects of the rice CDPK that show similarity to mammalian protein kinase C (PKC) and to other plant CDPKs: (a) Histone IIIS and PKC peptide-ser25 (19-31) are phosphorylated by rice CDPK. (b) The phosphorylation reaction is strictly dependent on calcium. (c) The activity of the rice CDPK is inhibited by either staurosporine or the PKC inhibitory peptide (19-36). (d) Addition of calmodulin has no effect on the activity of the enzyme; however, the CDPK is inhibited by the calmodulin antagonists trifluoperazine and W-7. (e) The rice CDPK reacts with a mammalian anti-PKC antibody in immunoblotting analysis. However, there is one major difference between the rice CDPK and other CDPKs: the rice CDPK is induced by GA, whereas no mammalian PKC or other plant CDPKs are known to be induced by any hormone.

Animals↗
PubMed1980

Hormonal Regulation of Lateral Bud (Tiller) Release in Oats (Avena sativa L.).

Stem segments containing a single node and quiescent lateral bud (tiller) were excised from the bases of oat shoots (cv. ;Victory') and used to study the effects of plant hormones on release of lateral buds and development of adventitious root primordia. Kinetin (10(-5) and 10(-6) molar) stimulates development of tillers and inhibits development of root primordia, whereas indoleacetic acid (IAA) (10(-5) and 10(-6) molar) causes the reverse effects. Abscisic acid strongly inhibits kinetin-induced tiller bud release and elon-gation and IAA-induced adventitious root development. IAA, in combination with kinetin, also inhibits kinetin-induced bud prophyll (outermost leaf of the axillary bud) elongation. The IAA oxidase cofactor p-coumaric acid stimulates lateral bud release; the auxin transport inhibitor 2,3,5-triiodo-benzoic acid and the antiauxin alpha (p-chlorophenoxy)-isobutyric acid inhibit IAA-induced adventitious root formation. Gibberellic acid is synergistic with kinetin in the elongation of the bud prophyll. In intact oat plants, tiller release is induced by shoot decapitation, geostimulation, or the emergence of the inflorescence. Results shown support the apical dominance theory, namely, that the cytokinin to auxin ratio plays a decisive role in determining whether tillers are released or adventitious roots develop. They also indicate that abscisic acid and possibly gibberellin may act as modulator hormones in this system.

Journal Article↗
PubMed2006

Dynamic integration of auxin transport and signalling.

Recent years have seen rapid progress in our understanding of the mechanism of action of the plant hormone auxin. A major emerging theme is the central importance of the interplay between auxin signalling and the active transport of auxin through the plant to create dynamic patterns of auxin accumulation. Even in tissues where auxin distribution patterns appear stable, they are the product of standing waves, with auxin flowing through the tissue, maintaining local pockets of high and low concentration. The auxin distribution patterns result in changes in gene expression to trigger diverse, context-dependent growth and differentiation responses. Multi-level feedback loops between the signal transduction network and the auxin transport network provide self-stabilising patterns that remain sensitive to the external environment and to the developmental progression of the plant. The full biological implications of the behaviour of this system are only just beginning to be understood through a combination of experimental manipulation and mathematical modelling.

Arabidopsis↗
PubMed2002

Regulation of the plant defence response in arbuscular mycorrhizal symbiosis.

The response of plants to arbuscular mycorrhizal fungi involves a temporal and spatial activation of different defence mechanisms. The activation and regulation of these defences have been proposed to play a role in the maintenance of the mutualistic status of the association, however, how these defences affect the functioning and development of arbuscular mycorrhiza remains unclear. A number of regulatory mechanisms of plant defence response have been described during the establishment of the arbuscular mycorrhizal symbiosis, including elicitor degradation, modulation of second messenger concentration, nutritional and hormonal plant defence regulation, and activation of regulatory symbiotic gene expression. The functional characterization of these regulatory mechanisms on arbuscular mycorrhiza, including cross-talk between them, will be the aim and objective of future work on this topic.

Biological Transport↗
PubMed2004

Stress hormone-independent activation and nuclear translocation of mitogen-activated protein kinases in Arabidopsis thaliana during ozone exposure.

Changing environmental conditions, atmospheric pollutants and resistance reactions to pathogens cause production of reactive oxygen species (ROS) in plants. ROS in turn trigger the activation of signaling cascades such as the mitogen-activated protein kinase (MAPK) cascade and accumulation of plant hormones, jasmonic acid, salicylic acid (SA), and ethylene (ET). We have used ozone (O3) to generate ROS in the apoplast of wild-type Col-0 and hormonal signaling mutants of Arabidopsis thaliana and show that this treatment caused a transient activation of 43 and 45 kDa MAPKs. These were identified as AtMPK3 and AtMPK6. We also demonstrate that initial AtMPK3 and AtMPK6 activation in response to O3 was not dependent on ET signaling, but that ET is likely to have secondary effects on AtMPK3 and AtMPK6 function, whereas functional SA signaling was needed for full-level AtMPK3 activation by O3. In addition, we show that AtMPK3, but not AtMPK6, responded to O3 transcriptionally and translationally during O3 exposure. Finally, we show in planta that activated AtMPK3 and AtMPK6 are translocated to the nucleus during the early stages of O3 treatment. The use of O3 to induce apoplastic ROS formation offers a non-invasive in planta system amenable to reverse genetics that can be used for the study of stress-responsive MAPK signaling in plants.

Active Transport, Cell Nucleus↗
PubMed2026

Comparative transcriptomics reveals hormone signaling and MADS-box genes in divergent development of inflorescences and tendrils in grapevine lateral shoots.

Hormone signaling and MADS-box genes regulate grapevine tendril and inflorescence growth divergence, offering molecular insights for managing tendril growth. Grapevine (Vitis vinifera L.) tendrils and inflorescences are homologous organs; however, their divergent development has important agronomic consequences because excessive tendril growth increases vineyard management costs. To explore the regulatory mechanisms, we compared the inflorescence-prone cultivar 'Einset Seedless' (ENT) with the tendril-prone cultivar 'Pinot Noir' (PN) using anatomical observation, transcriptome analysis of specific tendril nodes, and functional characterization of MADS-box genes. ENT exhibited a higher flowering rate at tendril nodes 1-4 than PN. Transcriptome profiling of specific tendril nodes uncovered 549 differentially expressed genes (DEGs) through an intersection/exclusion strategy, with Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment indicating that hormone and mitogen-activated protein kinase (MAPK) signaling were the primary candidates driving the divergence. To assess the spatiotemporal dynamics of these DEGs, we performed Mfuzz clustering, which revealed that multiple expression trajectories were highly consistent with the flowering gradient across different ENT and PN nodes. Plant hormone signal transduction was the predominantly enriched pathway across all dynamic clusters, highlighting the centrality of phytohormones in this process. Guided by this transcriptional evidence, we measured endogenous zeatin and gibberellin (GA₃) contents in the nodal tissues. Remarkably, the zeatin-to-GA₃ ratio not only paralleled the flowering gradient but also correlated with the cluster expression trajectories, providing physiological evidence for a cytokinin-gibberellin interaction model governing organ divergence. Additionally, we analyzed the differentially expressed transcription factors among the DEGs and identified a MADS-box gene, FRUITFULL-LIKE (VvFUL-L), which was markedly upregulated in PN tendrils. Heterologous overexpression of VvFUL-L in arabidopsis promoted early flowering and reduced inflorescence branching, suggesting its potential role in regulating lateral meristem development and affecting tendril formation. Collectively, these findings establish that Hormone Signaling, particularly cytokinin-GA crosstalk, and MADS-box regulators, such as VvFUL-L, are key regulators of inflorescence versus tendril growth in grapevines, providing a basis for future molecular and breeding studies.

Vitis↗
PubMed1983

Evidence for a Ca2+ gradient across the plasma membrane of wheat protoplasts.

Fluxes of Ca2+ across the plasma membrane of isolated wheat protoplasts have been measured both as net accumulation and as uptake under steady-state conditions. The ATPase inhibitors, orthovanadate and diethylstibesterol, and the divalent cation ionophore, A23187, were all found to enhance net Ca2+ accumulation by protoplasts. The uptake of Ca2+ under steady-state conditions was also stimulated by A23187 but relatively unaffected by a range of plant hormones or by red or far red light. Light treatments were compared to dark controls with protoplasts isolated from etiolated wheat. The results suggest that plant cells maintain a Ca2+ gradient across their plasma membrane but it appears not to be under phytochrome control.

Calcimycin↗
PubMed2006

Diverse signals converge at MAPK cascades in plant.

Mitogen-activated protein kinases (MAPKs) are important signal transducing enzymes that connects diverse receptors/sensors to a wide range of cellular responses in mammals, yeasts and plants. In recent years, a large number of different components of plant MAPK cascades were isolated. Molecular and biochemical studies have revealed that plant MAPKs play important role in the response to a broad variety of biotic and abiotic stresses, including wounding, pathogen infection, temperature, drought, salinity, but also in the signaling of plant hormones and the cell division. This review briefly summaries the recent research results about the cross-talk and complexity of MAP kinase cascades in plant obtained from functional analyses.

Acclimatization↗
PubMed1994

Characterization of an Arabidopsis cDNA for a soluble epoxide hydrolase gene that is inducible by auxin and water stress.

A cDNA (1122 bp) was isolated from a cDNA library prepared from Arabidopsis thaliana L. that had been subjected to drought stress for 1 h. The sequencing of a genomic clone corresponding to the cDNA and S1 mapping analysis revealed that the cDNA lacked the first 6 bp from its translational start (ATG). The resulting open reading frame encodes a polypeptide of 321 amino acids, and the calculated molecular weight of this polypeptide is 36,423 Da. The deduced amino acid sequence shows a high degree of similarity to C terminal halves of those of soluble epoxide hydrolases (sEHs) of human, mouse and rat, 35.5%, 34.1% and 33.1%, respectively. The cDNA was expressed in Escherichia coli cells, and the expressed protein migrates at 40 kDa when analyzed by SDS-PAGE. The recombinant protein at 40 kDa is much smaller than the mammalian sEH (58 kDa) but has characteristics of activity and inhibition similar to the mammalian sEHs when assayed with the substrate trans-stilbene oxide and the inhibitors 4-fluorochalcone oxide (4FCO), (2R,3R)-3-(4-nitrophenyl) glycidol (RRNPG), and (2S,3S)-3-(4-nitrophenyl)glycidol (SSNPG), which indicates that the cDNA did encode a soluble epoxide hydrolase of A. thaliana (AtsEH). Drought stress, but not heat or cold stress, slightly increased the accumulation of the mRNAs for AtsEH. The level of AtsEH transcripts increased strongly after treatment with a plant hormone, auxin (2,4-dichlorophenoxyacetic acid, 2,4-D; naphthalene-acetic acid, NAA; and indole-3-acetic acid, IAA) in young, pre-bolting plants. Treatment with cytokinin (6-benzylaminopurine, BA), abscisic acid (ABA) or gibberellin (GA3) had no detectable effect on AtsEH transcript levels. The transcripts for AtsEH gene were detected in the aerial vegetative organs of bolting plants (i.e. stems and leaves), but not in roots, flowers and seeds. The possible function of AtsEH is discussed. A similar sEH cDNA has recently been characterized in potato (Stapleton et al., 1994).

Amino Acid Sequence↗
PubMed2002

Jasmonic acid methyl ester induces the synthesis of a cytoplasmic/nuclear chito-oligosaccharide binding lectin in tobacco leaves.

In contrast to animal lectins, no evidence has indicated the occurrence of plant lectins, which recognize and bind "endogenous" receptors and accordingly are involved in recognition mechanisms within the organism itself. Here we show that the plant hormone jasmonic acid methyl ester (JAME) induces in leaves of Nicotiana tabacum (var. Samsun NN) the expression of a lectin that is absent from untreated plants. The lectin specifically binds to oligomers of N-acetylglucosamine and is detected exclusively in the cytoplasm and the nucleus. Both the subcellular location and specificity indicate that the Nicotiana tabacum agglutinin (called Nictaba) may be involved in the regulation of gene expression in stressed plants through specific protein-carbohydrate interactions with regulatory cytoplasmic/nuclear glycoproteins. Searches in the databases revealed that many flowering plants contain sequences encoding putative homologues of the tobacco lectin, which suggest that Nictaba is the prototype of a widespread or possibly ubiquitous family of lectins with a specific endogenous role.

Acetates↗
PubMed2002

Overexpression of a 9-cis-epoxycarotenoid dioxygenase gene in Nicotiana plumbaginifolia increases abscisic acid and phaseic acid levels and enhances drought tolerance.

The plant hormone abscisic acid (ABA) plays important roles in seed maturation and dormancy and in adaptation to a variety of environmental stresses. An effort to engineer plants with elevated ABA levels and subsequent stress tolerance is focused on the genetic manipulation of the cleavage reaction. It has been shown in bean (Phaseolus vulgaris) that the gene encoding the cleavage enzyme (PvNCED1) is up-regulated by water stress, preceding accumulation of ABA. Transgenic wild tobacco (Nicotiana plumbaginifolia Viv.) plants were produced that overexpress the PvNCED1 gene either constitutively or in an inducible manner. The constitutive expression of PvNCED1 resulted in an increase in ABA and its catabolite, phaseic acid (PA). When the PvNCED1 gene was driven by the dexamethasone (DEX)-inducible promoter, a transient induction of PvNCED1 message and accumulation of ABA and PA were observed in different lines after application of DEX. Accumulation of ABA started to level off after 6 h, whereas the PA level continued to increase. In the presence of DEX, seeds from homozygous transgenic line TN1 showed a 4-d delay in germination. After spraying with DEX, the detached leaves from line TN1 had a drastic decrease in their water loss relative to control leaves. These plants also showed a marked increase in their tolerance to drought stress. These results indicate that it is possible to manipulate ABA levels in plants by overexpressing the key regulatory gene in ABA biosynthesis and that stress tolerance can be improved by increasing ABA levels.

Abscisic Acid↗
PubMed1997

Root development: signaling down and around.

Because of its elegant simplicity, the Arabidopsis root has become a model for studying plant organogenesis. In this review we focus on recent results indicating the importance of signaling in root development. A role for positional information in root cell specification has been demonstrated by ablation analyses. Through mutational analysis, genes have been identified that play a role in radial pattern formation. The embryonic phenotypes of these mutants raised the possibility that division patterns in post-embryonic roots are dependent on signaling that originates during embryonic development. Analysis of expression of the SCARECROW gene indicates that it may play a role in this 'top-down' signaling process. Characterization of root epidermis development has led to the identification of negative regulators of root-hair formation. These appear to set up a prepattern which is reinforced by signaling by plant hormones.

Arabidopsis↗
PubMed2005

Simultaneous determination of multiple phytohormones in plant extracts by liquid chromatography-electrospray tandem mass spectrometry.

A rapid multiresidue method to quantify three different classes of plant hormones has been developed. The reduced concentrations of these metabolites in real samples with complex matrixes require sensitive techniques for their quantification in small amounts of plant tissue. The method described combines high-performance liquid chromatography with electrospray ionization tandem mass spectrometry. Deuterium-labeled standards were added prior to sample extraction to achieve an accurate quantification of abscisic acid, indole-3-acetic acid, and jasmonic acid in a single run. A simple method of extraction and purification involving only centrifugation, a partition against diethyl ether, and filtration was developed and the analytical method validated in four different plant tissues, citrus leaves, papaya roots, barley seedlings, and barley immature embryos. This method represents a clear advantage because it extensively reduces sample preparation and total time for routine analysis of phytohormones in real plant samples.

Carrier Proteins↗
PubMed1999

The gene encoding tobacco gibberellin 3beta-hydroxylase is expressed at the site of GA action during stem elongation and flower organ development.

Gibberellin 3beta-hydroxylase catalyzes the final step in the biosynthetic pathway leading to the plant hormone gibberellin (GA) and, therefore, the in vivo localization of this enzyme should give a direct indication of the site of synthesis of bioactive GAs in plants. We have isolated a cDNA clone, Nty (Nicotiana tabacum GA 3beta-hydroxylase), which encodes a putative GA 3beta-hydroxylase, by RT-PCR using RNA from tobacco shoot apices. Functional analysis, using an NTY protein expressed in Escherichia coli, revealed that Nty encoded an active GA 3beta-hydroxylase. A high expression level of Nty was observed in shoot apices, flowers, roots, young internodes but not in leaves or seeds. We performed more detailed expression analyses using in situ hybridization and histochemical analyses of the GUS activity in transgenic tobacco plants carrying an Nty promoter:GUS fusion gene. These studies revealed that expression of Nty was restricted to specific regions, including actively dividing and elongating cells in the various organs; rib meristem and elongation zones of shoot apices, tapetum and pollen grains in developing anthers and root tips, which are consistent with the sites of GA action. It is proposed that GA actions depend on the modulation of endogenous bioactive GA levels through the regulation of GA 3beta-hydroxylase expression in situ.

Amino Acid Sequence↗
PubMed1995

Analysis of LE-ACS3, a 1-aminocyclopropane-1-carboxylic acid synthase gene expressed during flooding in the roots of tomato plants.

The plant hormone ethylene is produced in response to a variety of environmental stresses. Previous work has shown that flooding or anaerobic stress in the roots of tomato plants caused an increase in the production of the ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC) in the roots, due to flooding-induced activity of ACC synthase (EC 4.4.1.14). RNA was extracted from roots and leaves of tomato plants flooded over a period of 48 h. Blot analysis of these RNAs hybridized with probes for four different ACC synthases revealed that the ACC synthase gene LE-ACS3 is rapidly induced in roots. LE-ACS2 is also induced, but at later times. The genomic clone for LE-ACS3 was isolated and sequenced. At all time points, the probe from the LE-ACS3 coding region hybridized to two bands in the RNA blots. Hybridization using the first and third introns of LE-ACS3 separately as probes indicate that flooding may inhibit processing of the LE-ACS3 transcript. Sequence homology analysis identified three putative cis-acting response elements in the promoter region, corresponding to the anaerobic response element from the maize adh1 promoter, the root-specific expression element from the cauliflower mosaic virus 35S promoter and a recognition element for chloroplast DNA binding factor I from the maize chloroplast ATP synthase promoter.

Amino Acid Sequence↗
PubMed2004

Ethylene insensitivity does not increase leaf area or relative growth rate in Arabidopsis, Nicotiana tabacum, and Petunia x hybrida.

The plant hormone ethylene plays a role in various growth related processes. In this detailed study of the vegetative growth of Arabidopsis, Nicotiana tabacum, and Petunia x hybrida plants, we show that ethylene insensitivity does not result in an increased total leaf area or relative growth rate (RGR) under optimal growth conditions. When grown in semiclosed containers, leaf area of ethylene-insensitive plants was larger compared to the wild type. This effect was caused by a buildup of ethylene inside these containers, which inhibited the growth of wild-type plants. Ethylene-insensitive Arabidopsis and N. tabacum plants had a lower biomass, which was mainly the result of a smaller seed mass. RGR of vegetative plants was not affected by ethylene insensitivity, but the underlying components of RGR differed; specific leaf area (leaf area per unit leaf mass) was higher, and unit leaf rate (growth rate per unit leaf area) was lower. The latter was a result of a slower rate of photosynthesis per unit leaf area in the ethylene-insensitive plants.

Arabidopsis↗
PubMed2004

MAX3/CCD7 is a carotenoid cleavage dioxygenase required for the synthesis of a novel plant signaling molecule.

BACKGROUND: Plant development is exquisitely environmentally sensitive, with plant hormones acting as long-range signals that integrate developmental, genetic, and environmental inputs to regulate development. A good example of this is in the control of shoot branching, where wide variation in plant form can be generated in a single genotype in response to environmental and developmental cues. RESULTS: Here we present evidence for a novel plant signaling molecule involved in the regulation of shoot branching. We show that the MAX3 gene of Arabidopsis is required for the production of a graft-transmissible, highly active branch inhibitor that is distinct from any of the previously characterized branch-inhibiting hormones. Consistent with its proposed function in the synthesis of a novel signaling molecule, we show that MAX3 encodes a plastidic dioxygenase that can cleave multiple carotenoids. CONCLUSIONS: We conclude that MAX3 is required for the synthesis of a novel carotenoid-derived long-range signal that regulates shoot branching.

Abscisic Acid↗
PubMed1985

Aleurain: a barley thiol protease closely related to mammalian cathepsin H.

We have isolated and sequenced a 1400-base-pair cDNA derived from gibberellic acid-treated aleurone cell mRNA. This sequence contains an open reading frame that would code for a protein of 361 amino acids. The carboxyl-terminal two-thirds of the predicted amino acid sequence is closely related to that of the rat lysosomal thiol protease cathepsin H; the initial 143 amino acids may code for a secretory peptide plus a prosegment. The expression of this aleurone thiol protease mRNA is unusual in that, in aleurone cells, its abundance is regulated by the plant hormones gibberellic acid and abscisic acid, but it is also expressed at high levels in leaf and root tissue. This protease may represent the equivalent of a plant lysosomal thiol protease.

Amino Acid Sequence↗