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PubMed2006

Organ-specific transcription of putative flavonol synthase genes of grapevine and effects of plant hormones and shading on flavonol biosynthesis in grape berry skins.

In order to investigate the control mechanism of flavonol biosynthesis of grapevine, we obtained five genomic sequences (FLS1 to FLS5) of putative flavonol synthase genes from Vitis vinifera cv. Cabernet Sauvignon. The mRNA of five FLSs accumulated in flower buds and flowers, while the mRNA of FLS2, FLS4, and FLS5 accumulated in small berry skins and then decreased toward veraison. At the ripening stage, the mRNA of only FLS4 and FLS5 accumulated again. This change in mRNA accumulation did not contradict the flavonol accumulation in the berry skins. Shading of the berries completely inhibited the increase in flavonol content and mRNA accumulation of FLS4, but did not affect the mRNA accumulation of FLS5. The effects of light and plant hormones on flavonol accumulation were different from those on anthocyanin accumulation. Thus flavonol biosynthesis appears to be under a different control system from that of anthocyanin biosynthesis.

Amino Acid Sequence↗
PubMed2001

Leaf senescence under various gravity conditions: relevance to the dynamics of plant hormones.

Effects of simulated microgravity and hypergravity on the senescence of oat leaf segments excised from the primary leaves of 8-d-old green seedlings were studied using a 3-dimensional (D) clinostat as a simulator of weightlessness and a centrifuge, respectively. During the incubation with water under 1-g conditions at 25 degrees C in the dark, the loss of chlorophyll of the segments was found dramatically immediately after leaf excision, and leaf color completely turned to yellow after 3-d to 4-d incubation. In this case kinetin (10 micromolar) was effective in retarding senescence. The application of simulated microgravity conditions on a 3-D clinostat enhanced chlorophyll loss in the presence or absence of kinetin. The loss of chlorophyll was also enhanced by hypergravity conditions (ca. 8 to 16 g), but the effect was smaller than that of simulated microgravity conditions on the clinostat. Jasmonates (JAs) and abscisic acid (ABA) promoted senescence under simulated microgravity conditions on the clinostat as well as under 1-g conditions. After 2-d incubation with water or 5-d incubation with kinetin, the endogenous levels of JAs and ABA of the segments kept under simulated microgravity conditions on the clinostat remained higher than those kept under 1-g conditions. These findings suggest that physiological processes of leaf senescence and the dynamics of endogenous plant hormone levels are substantially affected by gravity.

Abscisic Acid↗
PubMed2001

Production of multiple plant hormones from a single polyprotein precursor.

Some animal and yeast hormone genes produce prohormone polypeptides that are proteolytically processed to produce multiple copies of hormones with the same or different functions. In plants, four polypeptides have been identified that can be classed as hormones (intercellular chemical messengers) but none are known to be produced as multiple copies from a single precursor. Here we describe a polyprotein hormone precursor, present in tobacco plants, that gives rise to two polypeptide hormones, as often found in animals and yeast. The tobacco polypeptides activate the synthesis of defensive proteinase-inhibitor proteins in a manner similar to that of systemin, an 18-amino-acid polypeptide found in tomato plants. The two tobacco polypeptides are derived from each end of a 165-amino-acid precursor that bears no homology to tomato prosystemin. The data show that structurally diverse polypeptide hormones in different plant species can serve similar signalling roles, a condition not found in animals or yeast.

Amino Acid Sequence↗
PubMed1966

[Plant hormones].

Explore the source record for details and available documents.

Gibberellins↗
PubMed2002

An LRR receptor kinase involved in perception of a peptide plant hormone, phytosulfokine.

The sulfated peptide phytosulfokine (PSK) is an intercellular signal that plays a key role in cellular dedifferentiation and proliferation in plants. Using ligand-based affinity chromatography, we purified a 120-kilodalton membrane protein, specifically interacting with PSK, from carrot microsomal fractions. The corresponding complementary DNA encodes a 1021-amino acid receptor kinase that contains extracellular leucine-rich repeats, a single transmembrane domain, and a cytoplasmic kinase domain. Overexpression of this receptor kinase in carrot cells caused enhanced callus growth in response to PSK and a substantial increase in the number of tritium-labeled PSK binding sites, suggesting that PSK and this receptor kinase act as a ligand-receptor pair.

Amino Acid Sequence↗
PubMed1996

Plant hormones: brassinosteroids in the spotlight.

Recent studies on dwarf mutants of the model plant Arabidopsis thallana have provided convincing evidence that brassinosteroids-natural plant products similar to animal steroid hormones-are essential for normal plant growth and development.

Animals↗
PubMed1994

Transient inactivation of almond mandelonitrile lyase by 3-methyleneoxindole: a photooxidation product of the natural plant hormone indole-3-acetic acid.

A variety of plant growth regulators belonging to the auxin phytohormone family have been found to be good competitive inhibitors of the oxynitrilase from almonds, mandelonitrile lyase (MNL). The major natural auxin, indole-3-acetic acid (IAA), was found to inactivate MNL in a reaction following pseudo-first-order kinetics and dependent upon visible light. Inactivation results from the oxidative decarboxylation of IAA forming 3-methyleneoxidole (MOI). This compound has been synthesized and shown to produce active-site-directed inactivation of MNL, in a reaction following saturation kinetics with a KI of 37 +/- 8 microM and maximal kinact of 0.13 +/- 0.02 min-1. Inactivation protection is provided by the competitive inhibitors azide and benzoate, suggesting that the inactivation reaction is active-site-directed. This idea is substantiated by our determination that MOI is a competitive inhibitor of MNL with a Ki of 23 +/- 3 microM under steady-state turnover conditions, in reasonable agreement with the value obtained from the inactivation data. Several indole derivatives such as indoline, skatole, oxindole, and 3-methyloxindole are poor competitive inhibitors of MNL with dissociation constants 20-40-fold greater than that for MOI, suggesting a highly specific binding site for the IAA photooxidation product. The enzyme remains inactive following spin dialysis, indicating that a covalent adduct has been formed. However, approximately 30% activity was recovered in a 5-h period following dialysis, and a nearly quantitative recovery occurs in the presence of 2-mercaptoethanol or DTT, indicating that the adduct is labile.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehyde-Lyases↗
PubMed1994

Molecular characterization of two cloned nitrilases from Arabidopsis thaliana: key enzymes in biosynthesis of the plant hormone indole-3-acetic acid.

As in maize [Wright, A.D., Sampson, M. B., Neuffer, M. G., Michalczuk, L., Slovin, J. P. & Cohen, J. D. (1991) Science 254, 998-1000], the major auxin of higher plants, indole-3-acetic acid, is synthesized mainly via a nontryptophan pathway in Arabidopsis thaliana [Normanly, J., Cohen, J. D. & Fink, G. R. (1993) Proc. Natl. Acad. Sci. USA 90, 10355-10359]. In the latter species, the hormone may be accessible from the glucosinolate glucobrassicin (indole-3-methyl glucosinolate) and from L-tryptophan via indoleacetaldoxime under special circumstances. In each case, indole-3-acetonitrile is the immediate precursor, which is converted into indole-3-acetic acid through the action of nitrilase (nitrile aminohydrolase, EC 3.5.5.1). The genome of A. thaliana contains two nitrilase genes. Nitrilase I had been cloned earlier in our laboratory. The cDNA for nitrilase II (PM255) was cloned and encodes an enzyme that converts indole-3-acetonitrile to indole-3-acetic acid, the plant hormone. We show that the intracellular location as well as the expression pattern of the two A. thaliana nitrilases are distinctly different. Nitrilase I is soluble and is expressed throughout development, but at a very low level during the fruiting stage, while nitrilase II is tightly associated with the plasma membrane, is barely detectable in young rosettes, but is strongly expressed during bolting, flowering, and especially fruit development. The results indicate that more than one pathway of indole-3-acetic acid biosynthesis via indole-3-acetonitrile exists in A. thaliana and that these pathways are differentially regulated throughout plant development.

Amino Acid Sequence↗
PubMed1999

Role of the nonheme Fe(II) center in the biosynthesis of the plant hormone ethylene.

The final step of ethylene biosynthesis in plants is catalyzed by the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO). In addition to ACC, Fe(II), O2, CO2, and ascorbate are required for in vitro enzyme activity. Direct evidence for the role of the Fe(II) center in the recombinant avocado ACCO has now been obtained through formation of enzyme.(substrate or cofactor).NO complexes. These NO adducts convert the normally EPR-silent ACCO complexes into EPR-active species with structural properties similar to those of the corresponding O2 complexes. It is shown here that the ternary Fe(II)ACCO.ACC.NO complex is readily formed, but no Fe(II)ACCO.ascorbate.NO complex could be observed, suggesting that ascorbate and NO are mutually exclusive in the active site. The binding modes of ACC and the structural analog alanine specifically labeled with 15N or 17O were examined by using Q-band electron nuclear double resonance (ENDOR). The data indicate that these molecules bind directly to the iron through both the alpha-amino and alpha-carboxylate groups. These observations are inconsistent with the currently favored mechanism for ACCO, in which it is proposed that both ascorbate and O2 bind to the iron as a step in O2 activation. We propose a different mechanism in which the iron serves instead to simultaneously bind ACC and O2, thereby fixing their relative orientations and promoting electron transfer between them to initiate catalysis.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

The discovery of the chemical nature of the plant hormone auxin.

The concept of substances working as a chemical messenger among the plant tissues was guessed in the last quarter of the nineteenth century as a consequence of a series of observations and experiments concerning two important phenomena: the geotropism and the heliotropism. The work of Theophil Ciesielski, Charles and Francis Darwin, Julius von Sachs, Martinus Beijerinck and Julius Wiesner supplied the fundamental pillar to the modern plant physiology. Hans Fitting [1909] introduced the term "hormone", coined in 1902 to indicate a substance promoting chemical correlations among various organs of animals, in plant physiology for indicating a substance stimulating the development of the ovary of orchid flower. Paul Boysen-Jensen and Arpad Paál focused the occurrence of a growth substance that somehow regulated the positive curvature of oats coleoptiles, the distinctive feature of the phototropism. During the 1920s, a few Mitteleuropean botanists gave circumstantial evidence of such a substance before the Dutch physiologist Frits Went elaborated an experimental procedure for isolating it, and quantifying its physiological activity. Went's work crowned with success a half century of research and opened the door to the chemistry of the auxins. A next important step concerned the purification of sufficient amounts of substance for analytical purposes. Five years of attempts made by Hermann Dolk, Jan Haagen-Smit, F. Kögl and Kenneth Thimann had success and the "substance" was finally identified as indolacetic acid and named "auxin". This result delivered definitively the concept of plant growth from a secular mysticism and established a milestone in the modern plant physiology.

Indoleacetic Acids↗
PubMed2004

Characterization of HoMADS 1 and its induction by plant hormones during in vitro ovule development in Hyacinthus orientalis L.

To understand the molecular mechanism of ovule development, a MADS box gene, HoMADS 1 , has been isolated from the ovule tissues of Hyacinthus . Sequence comparison showed that HoMADS 1 is highly homologous to both class C and D genes. Furthermore, phylogenetic analysis suggests that HoMADS 1 is most likely a class D MADS box gene. RNA hybridization revealed that HoMADS 1 was exclusively expressed in the ovules. Over-expressing HoMADS 1 in transgenic Arabidopsis plants produced ectopic carpelloid structures, including ovules, indicating that HoMADS 1 is involved in the determination of carpel and ovule identities. Interestingly, during in vitro flowering, no HoMADS 1 mRNA was detected in the floral tissues at high level hormones in the media. However, HoMADS 1 mRNA accumulated in the floral tissues when the regenerated flowers were transferred to the media containing low level hormones which could induce in vitro ovule formation. Our data suggest that the induction of HoMADS 1 by plant hormones may play important roles during ovule initiation and development in the regenerated flower. Whether HoMADS 1 expression is also regulated by cytokinin and auxin during ovule development in planta remains to be investigated.

Amino Acid Sequence↗
PubMed2006

Different plant hormones regulate similar processes through largely nonoverlapping transcriptional responses.

Small-molecule hormones govern every aspect of the biology of plants. Many processes, such as growth, are regulated in similar ways by multiple hormones, and recent studies have revealed extensive crosstalk among different hormonal signaling pathways. These results have led to the proposal that a common set of signaling components may integrate inputs from multiple hormones to regulate growth. In this study, we tested this proposal by asking whether different hormones converge on a common set of transcriptional targets in Arabidopsis seedlings. Using publicly available microarray data, we analyzed the transcriptional effects of seven hormones, including abscisic acid, gibberellin, auxin, ethylene, cytokinin, brassinosteroid, and jasmonate. A high-sensitivity analysis revealed a surprisingly low number of common target genes. Instead, different hormones appear to regulate distinct members of protein families. We conclude that there is not a core transcriptional growth-regulatory module in young Arabidopsis seedlings.

Abscisic Acid↗