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PubMed2005

A genetic test of bioactive gibberellins as regulators of heterosis in maize.

This study tested the hypothesis that gibberellin levels were responsible for the superior growth habit of hybrids (i.e., heterosis). If this were true, plants reduced in their capacity to produce gibberellin, such as maize plants homozygous for dwarf1 (d1), should display a lesser heterotic response. The d1 mutation was introgressed into two inbred lines of maize, B73 and Mo17, for seven generations. Plants segregating for the dwarf phenotype were produced both by self-fertilizing the introgressed inbred lines and by making reciprocal crosses between them to produce hybrids. Measurements were made of several physical traits. The results indicated that the hybrid dwarf plants experienced no loss of heterosis relative to their normal siblings. These results exclude the possibility that modulation of bioactive gibberellins is a major underlying basis of the heterotic response.

Crosses, Genetic↗

PubMed1999

Lovastatin inhibits the production of gibberellins but not sterol or carotenoid biosynthesis in Gibberella fujikuroi.

Sterols, carotenoids and gibberellins are synthesized after the reduction of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) to mevalonate in different subcellular compartments of the fungus Gibberella fujikuroi. Lovastatin inhibits growth in many organisms, presumably because of the inhibition of the synthesis of essential terpenoids. However, in G. fujikuroi growth of the mycelia and sterol and carotenoid content were not affected by the presence of lovastatin. Nevertheless, lovastatin did inhibit the accumulation of gibberellins in the culture medium; this inhibition, however, was counteracted by the addition of mevalonate to the medium. The conversion of HMG-CoA to mevalonate in cell-free extracts was inhibited by 10 nM lovastatin. Since G. fujikuroi apparently possesses a single gene for HMG-CoA reductase, as shown by Southern hybridization and PCR amplification, it was concluded that the biosynthesis of sterols, carotenoids and gibberellins shares a single HMG-CoA reductase, but the respective subcellular compartments are differentially accessible to lovastatin.

Acyl Coenzyme A↗

PubMed1966

Effect of Cycocel derivatives and gibberellin on choline kinase and choline metabolism.

Cycocel stimulated the activity of partial purified choline kinase from spinach or squash leaves, but it inhibited the activity of yeast choline kinase. The activity of different Cycocel analogs on plant growth corresponded to their stimulatory effect on the isolated choline kinase. Cycocel had no effect upon the activity of a plant phosphatase which hydrolyzed phosphorylcholine nor upon adenosine triphosphatase from wheat roots or leaves. Gibberellin A(3) inhibited choline kinase activity and reversed the stimulatory effect of Cycocel on the kinase. Total choline kinase activity per squash plant was not greatly increased by Cycocel treatment. However, on the basis of fresh weight, total kinase activity was increased by Cycocel treatment. Gibberellin A(3) partially reversed these increases. Treatment with Cycocel plus indoleacetic acid resulted in a large increase in choline kinase activity. The same distribution of tracer among phosphorylcholine, choline and betaine was observed when either phosphorylcholine-C(14) or choline-C(14) was fed to barley or wheat roots. Cycocel stimulated the incorporation of choline-C(14) into the insoluble fraction and into lipids. Cycocel inhibited phosphorylcholine uptake by roots. Thus Cycocel stimulated choline kinase activity and the utilization of choline-C(14). The effect of Cycocel upon kinase activity in vivo and in vitro was reversed by gibberellin A(3).

Choline↗

PubMed1960

Response of Cupressus funebris tissue cultures to gibberellins.

Gibberellins are a specific growth requirement of tissue cultures derived from the staminate cones of Cupressus funebris. The tissue originally required coconut milk for growth. However, a mixture of acid-hydrolyzed casein hydrolyzate and gibberellins replaces the coconut milk entirely and permits even better growth. It is tentatively suggested that coconut milk contains gibberellins or related substances and that these substances are involved in the nitrogen metabolism of the tissue.

Cupressus↗

PubMed1981

The effect of culture medium composition and incubation time on synthesis of gibberellin-like substances by bacteria isolated from the roots of pine seedlings (Pinus silvestris L.).

It was found that synthesis of gibberellin-like substances by ten strains of Coryneform bacteria isolated from the roots of pine seedlings depended on both the composition of the medium and incubation time. More of these substances were produced in mineral medium with glucose in complex medium with casamino acids and yeast extract. Most gibberellin-like substances were found in 7 or 14-day old cultures. Culture supernatant fluids of most of the bacteria tested contained several gibberellin-like substances which on chromatograms run with the solvent system benzene, acetic acid (10:3, v/v) were located at Rf 0.0-0.3; 0.4-0.6 and 0.8-1.0.

Actinomycetales↗

PubMed1981

Gibberellin- and cytokinin-like activities in marine algae from central Mediterranean.

The distribution of gibberellin- and cytokinin-like activities in twenty-one species of mediterranean algae belonging to Phaeophyta and Rhodophyta has been investigated. Fractions containing each of these activities have been obtained by partitioning aqueous-methanolic extracts of algae against ethyl acetate and butanol successively at different pH values. The stimulation or inhibition of amaranthin synthesis in Amaranthus sp. seedlings have been used a biological tests to assay the cytokinin- or gibberellin-like activities respectively. One or both these two hormonal activities have been detected in all species examined. While cytokinin-like activity has been found with the same frequency in the two phyla, the gibberellin-like activity was less frequent in Phaeophyta.

Biological Assay↗

PubMed1995

[Studies on fused recombination of Gibberella fujikuroi--gibberellin-producing strain].

A pair of nutrient complementary auxotrophic mutants were used as fusion parents. Their protoplasts were prepared enzymatically and PEG4000 was used as fusion agent. The prototrophic recombinants were selected directly on the minimal regeneration medium. The recombination frequency was about 10(-7). Some unstable heterocaryons were occurred and the frequency was about 10(-5)-10(-6). Mutation of pigment, hyphae morphology and gibberellin production were induced through the fused recombination. The positive mutation, negative mutation of gibberellin yield among the recombinants were 15.3% and 53.1% respectively. Gibberellin yields of recombinants signed RN2 and RG14 were over 25% than that of the prototrophic parent 207 strain.

Cell Fusion↗

PubMed1994

Purification and partial amino-acid sequence of gibberellin 20-oxidase from Cucurbita maxima L. endosperm.

Gibberellin (GA) 20-oxidase was purified to apparent homogeneity from Cucurbita maxima endosperm by fractionated ammonium-sulphate precipitation, gel-filtration chromatography and anion-exchange and hydrophobic-interaction high-performance liquid chromatography (HPLC). Average purification after the last step was 55-fold with 3.9% of the activity recovered. The purest single fraction was enriched 101-fold with 0.2% overall recovery. Apparent relative molecular mass of the enzyme was 45 kDa, as determined by gel-filtration HPLC and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, indicating that GA 20-oxidase is probably a monomeric enzyme. The purified enzyme degraded on two-dimensional gel electrophoresis, giving two protein spots: a major one corresponding to a molecular mass of 30 kDa and a minor one at 45 kDa. The isoelectric point for both was 5.4. The amino-acid sequences of the amino-terminus of the purified enzyme and of two peptides from a tryptic digest were determined. The purified enzyme catalysed the sequential conversion of [14C]GA12 to [14C]GA15, [14C]GA24 and [14C]GA25, showing that carbon atom 20 was oxidised to the corresponding alcohol, aldehyde and carboxylic acid in three consecutive reactions. [14C]Gibberellin A53 was similarly converted to [14C]GA44, [14C]GA19, [14C]GA17 and small amounts of a fourth product, which was preliminarily identified as [14C]GA20, a C19-gibberellin. All GAs except [14C]GA20 were identified by combined gas chromatography-mass spectrometry. The cofactor requirements in the absence of dithiothreitol were essentially as in its presence (Lange et al., Planta 195, 98-107, 1994), except that ascorbate was essential for enzyme activity and the optimal concentration of catalase was lower.

Amino Acid Sequence↗

PubMed1976

Localization of phytochrome in etioplasts and its regulation in vitro of gibberellin levels.

Etioplasts isolated from barley leaves and purified on a Sephadex G-50 (coarse) column were characterized by electron microscopy and nucleic acid analysis. The majority of etioplasts retained an intact outer envelope, and contamination by other fragments was extremely low. The level of gibberellin-like substances extractable from intact etioplast suspensions was enhanced within 5 min of the termination of a saturating red irradiation, and the response was far-red reversible. Ultra-sonication caused a 3-fold increase in extractable activity both in dark control suspension and suspensions treated with red light. It is concluded that phytochrome, as a function of its interconversions, probably causes the transport of gibberellin from inside the etioplast into the surrounding medium. This leads to increased production of active gibberellins, possibly by release of feedback control of late steps of the biosynthetic pathway. Dual wavelength difference spectrophotometry has demonstrated the presence of a proportion of total cellular phytochrome within the etioplast.

Journal Article↗

PubMed2001

Involvement of cortical microtubules in plastic extension regulated by gibberellin in Lemna minor root.

We aimed to analyze the rheological characteristics during elongation of the root segments in Lemna minor. The elastic component of segment elongation (EC) increased for the first 6 h, and then almost stopped. However, the plastic component of the segment elongation (PC) began to rapidly increase from 6 h onwards. Uniconazole-P, a gibberellin biosynthesis inhibitor, inhibited the total elongation of root segments (TE), and this inhibition was mainly caused by suppression of the rapid increase in the PC after 6 h. Concomitant with this inhibition, the cortical microtubule (CMT) array within root epidermal cells became disorganized in the presence of uniconazole-P from 6 h onwards. Adding GA3 abolished the inhibition of TE by uniconazole-P treatment, and this recovery was caused not by the increase in the EC but by an increase in the PC. Furthermore, the CMT arrays also recovered their characteristic organization in the presence of GA3. These findings suggest that endogenous gibberellin accelerates TE by activating the PC via control of CMT arrays. This conclusion is also supported by rheological analysis where propyzamide was used to disrupt microtubules. We suggest that endogenous gibberellin controls the PC via its influence over the transverse arrangement of CMTs.

Benzamides↗

PubMed1993

Distribution of Gibberellins in Lathyrus odoratus L. and Their Role in Leaf Growth.

In sweet pea (Lathyrus odoratus L.) the mutant allele l reduced the level of gibberellin A1 (GA1) in expanding leaflets and resulted in smaller, more oval leaflets compared with the wild type. The apical portions of 6-d-old wild-type (L) seedlings also contained less GA1 and produced smaller, more oval leaflets than did comparable 20-d-old L seedlings. Application of GA1 markedly altered leaflet shape and, at certain dosages, restored the wild-type shape and size to leaflets of the l (dwarf) mutant. Taken together, these observations indicate that GA1 performs a regulatory role in the control of leaf growth in this species. The levels of GA1 precursors in the wild type were also determined. Rapidly expanding internodes contained much more gibberellin A19 (GA19) than gibberellin A20 (GA20), whereas the opposite was true for expanding leaflets. Although in entire apical portions of established seedlings the level of GA20 exceeded that of GA19, apical portions of very young seedlings contained more GA19 than GA20. Basal stem tissue of established seedlings also contained substantially more GA19 than GA20 or GA1. Both stems and leaflets from the basal portion of the plant contained much less GA20 and GA1 than did the rapidly expanding apical tissue. The implications of these results for the regulation of GA1 biosynthesis are discussed.

Journal Article↗

PubMed1966

Gibberellins of sugarcane.

In our hands a phosphate buffered celite column has given an adequate separation of GA(1) and GA(3). These 2 gibberellins are normally very difficult to separate. Young sugarcane growing under moisture stress contains at least 2 gibberellin-like substances. One is suspected to be GA(5). The other is unknown but has high activity in the barley endosperm assay and is neither GA(1) nor GA(3). Four-month-old cane contains 2 major growth promoters. From their chromatographic, fluorimetric and biological properties these are thought to be GA(1) and GA(3). Rapidly growing 6-month-old cane has a surprisingly low level of gibberellin-like substances.

Journal Article↗

PubMed1967

Barley endosperm bioassay for gibberellins. I. Parameters of the response system.

Parameters of the bioassay based on the gibberellin-induced reducing sugar release of barley endosperm were investigated. Procedures for the rapid handling and processing of up to several hundred treatments without loss in sensitivity of the test are described, and the effects of variations in many aspects of the bioassay were assessed.In general, the variations in varieties, techniques, additives, conditions, and even gibberellins, all illustrate the stability, sensitivity, and adaptability of the hormone-induced response and emphasize its utility as a gibberellin bioassay.

Journal Article↗

PubMed1967

Preparation of radioactive gibberellin a(1) and its metabolism in dwarf peas.

Gibberellin A(1)-3,4-(3)H was prepared by selective catalytic reduction of gibberellic acid with a mixture of tritium and hydrogen. (3)H-GA(1) was applied at physiological concentrations to dwarf peas and the metabolism of the hormone was investigated. (3)H-GA(1) was converted to an acidic, biologically active compound. Radioactive but biologically inactive compounds were also found in the neutral fraction and could not be converted to acidic gibberellins by hydrolysis. No attachment of gibberellin to any macromolecular fraction was evident.

Journal Article↗

PubMed1968

Gibberellin-like Substances From Vegetative Tissue of a Conifer, Arizona Cypress.

Vegetative shoots of Arizona cypress (Cupressus arizonica Greene) were found to contain an estimated 40 to 70 mug of gibberellin-like activity per kg. Based on elution patterns of silicic acid and celite partition columns, mobilities on thin layer chromatograms and specificity of the cucumber, d-3 dwarf maize, dwarf pea, and barley half seed bioassays it was possible to determine that the tissue contained at least 5 acidic, ethyl acetate-soluble gibberellin-like substances. The major one would appear to be GA(3). In addition, GA(9), GA(4), and/or GA(7)-like compounds, and 2 unidentified gibberellin-like substances are present.

Journal Article↗

PubMed1968

Endogenous gibberellins of a radiation induced single gene dwarf mutant of bean.

The distribution of endogenous gibberellins in Dwarf-1, a single gene dwarf mutant of Mexico 80-R red beans, was studied. Parallel extraction and fractionation of seeds of this mutant and those of a normal homozygous line followed by thin layer chromatography and bioassays using Rumex obtusifolius, wheat seed endosperm and dwarf bean plants revealed that a stem elongation control factor was contained in the non-acidic fraction from normal, but not from Dwarf-1, seeds. It was concluded that the single gene mutation causes a block either in gibberellin precursor formation or in production of a non-acidic fraction gibberellin-like substance.

Journal Article↗

PubMed1968

Fate of radioactive gibberellin a(1) in maturing and germinating seeds of peas and Japanese morning glory.

Radioactive gibberellin A(1) ((3)H-GA(1)) was injected into excised fruits of peas and Japanese morning glory. These were then grown in sterile culture to maturity and the label was followed in the seeds during further development and subsequent germination. During development of both pea and morning-glory seeds a large part of the radioactivity became associated with the aqueous fraction, while another part of the (3)H-GA(1) was converted into 2 new, acidic, biologically active compounds, designated X(1) and X(2). A relatively small part of the neutral compounds could be converted back to (3)H-GA(1), X(1), and X(2) by means of mild acid hydrolysis. During germination of pea and morning-glory seeds, part of the bound compounds was released in the form of (3)H-GA(1), X(1) and X(2) while, particularly during rapid seedling growth, a further conversion of (3)H-GA(1), mainly to X(1), took place. In pea seedlings, growth during the first 2 to 3 days after imbibition was not affected by Amo-1618, an inhibitor of gibberellin biosynthesis. This, in conjunction with the findings on the interconversions between free and bound (3)H-GA(1) suggests that, at least in peas, early seedling growth may at least partly be regulated by gibberellins released from a bound form which was formed during seed development.

Journal Article↗

PubMed1971

Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L: VIII. Early Effects of Gibberellin A(3) and Abscisic Acid on Ultrastructure.

Using the electron microscope, we compared the effects of abscisic acid and gibberellin A(3) on excised buds from resting potato (Solanum tuberosum L.) tubers. Cells of abscisic acid-treated buds became progressively more vacuolated during a 12-hour time course study as compared with control (water) and gibberellin A(3)-treated buds. Concentric configurations of endoplasmic reticulum were present in apical cells of freshly excised buds. After about 6 hours these configurations began to open and disperse, and after 12 hours, intact concentric configurations were no longer evident. Both abscisic acid and gibberellin A(3) induced opening and dispersal of the concentric configurations, sometimes as early as 0.5 hour after excision and treatment with hormones.

Journal Article↗