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PubMed1986

Identification of Pea Gibberellins by Studying [C]GA(12)-Aldehyde Metabolism.

Experiments were designed to test the hypothesis that the labeled products recovered from plant tissue incubated with [(14)C]GA(12)-7-aldehyde ([(14)C]GA(12)ald) would serve as appropriate [(14)C]markers for the recovery of naturally-occurring gibberellins (GAs). The [(14)C]GA(12)ald (about 200 millicuries per millimole) was synthesized from pumpkin endosperm using [4,5-(14)C]mevalonic acid. It was added to the adaxial surface of isolated pea cotyledons at 22 days after flowering. Products recovered after 0.5 and 4.0 hour incubations yielded four major peaks which were separated by high performance liquid chromatography (HPLC). These products were purified by multiple-column HPLC using on-line radioactivity detection. They were then added as [(14)C]markers to two unlabeled pea extracts. In general, preparative HPLC followed by further HPLC purification resulted in a single UV-absorbing peak co-eluting with each [(14)C]marker. These [(14)C] and UV-absorbing peaks were shown to contain GA(53), GA(44), GA(20), GA(19), and GA(17) by GC-MS. The finding of GA(53) is novel; all others have previously been found in pea. Endogenous GAs of pea were thus readily detected using [(14)C]GA(12)ald metabolites as [(14)C]markers to recover naturally occurring GAs suggesting that the method may be applicable in detecting naturally occurring GAs in other species.

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PubMed1986

Photoperiod modification of [C]gibberellin a(12) aldehyde metabolism in shoots of pea, line g2.

In G2 peas (Pisum sativum L.) apical senescence occurs only in long days (LD), and indeterminate growth is associated with elevated gibberellin (GA) levels in the shoot in short days (SD). Metabolism of GA(12) aldehyde was investigated by feeding shoots grown in SD or LD with [(14)C]GA(12) aldehyde through the cut end of the stem for 0.5 to 6 hours in the light and analyzing the tissue extract by high performance liquid chromatography. More radioactive products were detected than can be accounted for by the two GA metabolic pathways previously known to be present in peas. Three of the major products appear to be GA conjugates, but an additional pathway(s) of GA metabolism may be present. The levels of putative C(20) GAs, [(14)C]GA(53), [(14)C]GA(44), [(14)C]GA(19), and/or [(14)C] GA(17), were all elevated in SD as compared to LD. Putative [(14)C]GA, was slightly higher in LD than in SD. Putative [(14)C]GA(53) was a major metabolite after 30 minutes of treatment in SD but had declined after longer treatment times to be replaced by elevated levels of putative [(14)C] GA(44) and [(14)C]GA(19/17). Metabolism of GA(20) was slow in both photoperiods. Although GA(20) and GA(19) are the major endogenous GAs as determined by gas chromatography-mass spectrometry, putative [(14)C]GA(20) and [(14)C]GA(19) were never major products of [(14)C]GA(12) aldehyde metabolism. Thus, photoperiod acts in G2 peas to change the rate of GA(53) production from GA(12) aldehyde, with the levels of the subsequent GAs on the 13-OH pathway being determined by the amount of GA(53) being produced.

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PubMed1986

Gibberellin metabolism in cell-free extracts from spinach leaves in relation to photoperiod.

Cell-free extracts capable of converting [(14)C]-labeled gibberellins (GAs) were prepared from spinach (Spinacia oleracea L.) leaves. [(14)C]-labeled GAs, prepared enzymically from [(14)C]mevalonic acid, were incubated with these extracts, and products were identified by gas chromatography-mass spectrometry. The following pathway was found to operate in extracts from spinach leaves grown under long day (LD) conditions: GA(12) --> GA(53) --> GA(44) --> GA(19) --> GA(20). The pH optima for the enzymic conversions of [(14)C]GA(53), [(14)C]GA(44) and [(14)C]GA(19) were approximately 7.0, 8.0, and 6.5, respectively. These three enzyme activities required Fe(2+), alpha-ketoglutarate and O(2) for activity, and ascorbate stimulated the conversion of [(14)C]GA(53) and [(14)C]GA(19). Extracts from plants given LD or short days (SD) were examined, and enzymic activities were measured as a function of exposure to LD, as well as to darkness following 8 LD. The results indicate that the activities of the enzymes oxidizing GA(53) and GA(19) are increased in LD and decreased in SD or darkness, but that the enzyme activity oxidizing GA(44) remains high irrespective of light or dark treatment. This photoperiodic control of enzyme activity is not due to the presence of an inhibitor in plants grown in SD. These observations offer an explanation for the higher GA(20) content of spinach plants in LD than in SD.

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PubMed1986

Gibberellins in Suspensors of Phaseolus coccineus L. Seeds.

Analysis of extracts from 6300 (1.2 grams fresh weight) Phaseolus coccineus suspensors by combined gas chromatography-mass spectrometry has demonstrated the presence of five C(19)-gibberellins, GA(1), GA(4), GA(5), GA(6), GA(8), and one C(20)-GA, GA(44). The major GAs present were GA(1) and GA(8). Data are discussed in relation to previous results obtained in P. coccineus seed as well as in the embryo-suspensor system.

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PubMed1986

Identification of endogenous gibberellins from sorghum.

Gibberellins (GA) A(1), A(19), and A(20) were identified in shoot cylinders containing the apical meristems from sorghum (Sorghum bicolor L.). Extracts were purified by sequential SiO(2) partition chromatography and reversed-phase C(18) high performance liquid chromatography and biologically active (dwarf rice cv Tan-ginbozu microdrop assay) fractions were subjected to gas chromatography-selected ion monitoring. Based on the use of [(3)H]GA and [(2)H](d(2))GA internal standards, amounts of GA(1), GA(19), and GA(20) were estimated to be 0.7, 8.8, and 1.5 namograms per gram dry weight of tissue, respectively.

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PubMed1987

Metabolism of [H]Gibberellin A(5) by Immature Seeds of Apricot (Prunus armeniaca L.).

Immature seeds of apricot (Prunus armeniaca L.) were fed the native gibberellin A(5) (GA(5)) as 1- and 1,2-[(3)H]GA(5) (5.3 Curies per millimole to 16 milliCuries per millimole) at doses (42 nanograms to 10.6 micrograms per seed) 2 to 530 times the expected endogenous level. After 4 days of incubation, seeds were extracted and free [(3)H]GA-like metabolites were separated from the highly H(2)O-soluble [(3)H]metabolites. For high specific activity feeds the retention times (Rts) of radioactive peaks were compared with Rts of authentic GAs on sequential gradient-eluted --> isocratic eluted reversed-phase C(18) high performance liquid chromatography (HPLC) -radiocounting (RC). From high substrate feeds (530 and 230 x expected endogenous levels) HPLC-RC peak groupings were subjected to capillary gas chromatography-selected ion monitoring (GC-SIM), usually six characteristic ions. The major free GA metabolites of [(3)H] GA(5) were identified as GA(1), GA(3), and GA(6) by GC-SIM. The major highly water soluble metabolite of [(3)H]GA(5) at all levels of substrate GA(5) had chromatographic characteristics similar to authentic GA(1)-glucosyl ester. Expressed as a percentage of recovered radioactivity, low substrate [(3)H]GA(5) feeds (2 x expected endogenous level) yielded a broad spectrum of metabolites eluting at the Rts where GA(1), GA(3), GA(5) methyl ester, GA(6), GA(22), GA(29) (17, 14, 1.6, 7, 1.1, 0.5%, respectively) and GA glucosyl conjugates of GA(1), GA(3), GA(5), and GA(8) (33, 11, 1, 0.1%, respectively) elute. Metabolites were also present at Rts where GA glucosyl conjugates of GA(6) and GA(29) would be expected to elute (8 and 0.1%, respectively). Only 5% of the radioactivity remained as GA(5). Increasing substrate GA(5) levels increased the proportion of metabolites with HPLC Rts similar to GA(1), GA(6), and especially GA(1) glucosyl ester, primarily at the expense of metabolites with HPLC Rts similar to GA(3), GA(3)-glucosyl ester, and a postulated conjugate of GA(6). There was evidence that high doses of substrate GA(5) induced new metabolites which often, but not always, differed from GA(1), GA(3), and GA(6) in HPLC Rt. These same metabolites, when analyzed by GC-SIM yielded m/e ions the same as the M(+) and other characteristic m/e ions of the above GAs, albeit at differing GC Rt and relative intensities.

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PubMed1987

Effects of Chilling and ABA on [H]Gibberellin A(4) Metabolism in Somatic Embryos of Grape (Vitis vinifera L. x V. rupestris Scheele).

Previous work has indicated that changes in gibberellin (GA) metabolism may be involved in chilling-induced release from dormancy in somatic embryos of grape (Vitis vinifera L. x V. rupestris Scheele). We have chilled somatic embryos of grape for 2, 4, or 8 weeks, then incubated them with [(3)H]GA(4) (of high specific activity, 4.81 x 10(10) becquerel per millimole) for 48 hours at 26 degrees C. Chilling had little effect on the total amount of free [(3)H]GA-like metabolites formed during incubation at 26 degrees C, but did change the relative proportions of individual metabolites. The amount of highly water-soluble [(3)H] metabolites formed at 26 degrees C decreased in embryos chilled for 4 or 8 weeks. The concentration of endogenous GA precursors (e.g., GA(12) aldehyde-, kaurene-, and kaurenoic acid-like substances) increased in embryos chilled for 4 or 8 weeks. Treatment with abscisic acid (ABA) (known to inhibit germination in grape embryos) concurrent with [(3)H]GA(4) treatment at 26 degrees C, reduced the uptake of [(3)H] GA(4) but had little effect on the qualitative spectrum of metabolites. However, in the embryos chilled for 8 weeks and then treated with ABA for 48 hours at 26 degrees C, there was a higher concentration of GA precursors than in untreated control embryos. Chilled embryos thus have an enhanced potential for an increase in free GAs through synthesis from increased amounts of GA precursors, or through a reduced ability to form highly water-soluble GA metabolites (i.e., GA conjugates or polyhydroxylated free GAs).

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PubMed1987

Identification of Gibberellins in Norway Spruce (Picea abies [L.] Karst.) by Combined Gas Chromatography-Mass Spectrometry.

Gibberellins A(1) (GA(1)), A(3) and A(9) were identified from extracts of shoots of 6-month old Norway spruce (Picea abies) seedlings by the use of sequential reverse and normal phase high performance liquid chromatography (HPLC), bioassay, radioimmunoassay (RIA) and combined gas chromatography-mass spectrometry (GC-MS). The bioassay and RIA were used after fractionation by HPLC to detect the GA-containing fractions, which were then examined by GC-MS. The GAs identified are considered to be endogenous.

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PubMed1987

Gibberellin-mediated synergism of xylogenesis in lettuce pith cultures.

Major gibberellins (GAs) in lettuce (Lactuca sativa L. cv Romaine) pith explants have been identified by gas chromatography-mass spectrometry (GC-MS) or GC-selected ion monitoring (GC-SIM) as GA(1), 3-epi-GA(1), GA(8), GA(19), and GA(20). Treatment of pith explants with indole-3-acetic acid (IAA) (57 micromolar) plus kinetic (0.5 micromolar) induced xylogenesis. In this xylogenic treatment, the concentration of a biologically active, polar GA-like substance(s) increased during the first 2 days of culture, although all of the above GAs decreased (as measured by GC-SIM). In non-xylogenic treatments, where explants were cultured without exogenous hormones, or with IAA or kinetin alone, the concentration of the biologically active, polar GA-like substance(s) decreased during the first two days of culture, as did all of the above GAs (as measured by GC-SIM). Treatment of pith explants with exogenous GA(1) alone did not induce xylogenesis, but GA(1) at very low concentrations (0.0014 and 0.003 micromolar) synergized xylogenesis in the IAA plus kinetin-treated cultures. These results suggest that changes in the concentration of certain endogenous GAs may be involved in xylogenesis mediated by IAA plus kinetin in lettuce pith cultures.

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PubMed1987

Gibberellins in Relation to Growth and Flowering in Pharbitis nil Chois.

Flowering can be modified by gibberellins (GAs) in Pharbitis nil Chois. in a complex fashion depending on GA type, dosage, and the timing of treatment relative to a single inductive dark period. Promotion of flowering occurs when GAs are applied 11 to 17 hours before a single inductive dark period. When applied 24 hours later the same GA dosage is inhibitory. Thus, depending on their activity and the timing of application there is an optimum dose for promotion of flowering by any GA, with an excessive dose resulting in inhibition. Those GAs highly promotory for flowering at low doses are also most effective for stem elongation (2,2-dimethyl GA(4) >> GA(32) > GA(3) > GA(5) > GA(7) > GA(4)). However, the effect of GAs on stem elongation contrasts markedly with that on flowering. A 10- to 50-fold greater dose is required for maximum promotion of stem elongation, and the response is not influenced by time of application relative to the inductive dark period. These differing responses of flowering and stem elongation raise questions about the use of relatively stable, highly bioactive GAs such as GA(3) to probe the flowering response. It is proposed that the ;ideal' GAs for promoting flowering may be highly bioactive but with only a short lifetime in the plant and, hence, will have little or no effect on stem elongation.

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PubMed1987

Gibberellins, Endogenous and Applied, in Relation to Flower Induction in the Long-Day Plant Lolium temulentum.

Changes in endogenous gibberellin-like substances (GAs) and related compounds in the shoot apices of Lolium temulentum during and after flower induction by one long day was examined for plants grown in three consecutive years. The total GA level in the shoot apical tissue was high (up to 42 micrograms per gram dry weight, or 3 x 10(-5) molar GA(3) equivalents), increasing several-fold on the day after the long day and then declining. Of the many GA-like substances present, the putative polyhydroxylated components-with HPLC retention times between those of GA(8) (three hydroxyls) and GA(32) (four hydroxyls), and accounting for about a quarter of the total GA activity-were most consistent and striking in their changes. Their level in the apices increased 3- to 5-fold on the day after the long day and then subsided. When various GAs were applied to plants in noninductive short days, flower initiation was induced by several, most notably by GA(32), GA(5), 2,2-dimethyl GA(4), GA(3), and GA(7). GA(32) was most like one long day in eliciting a strong flowering response while having little effect on stem growth, whereas GA(1) had the opposite effect. It is suggested that highly hydroxylated C-19 GAs may play a central role in the induction of flowering in this long-day plant.

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PubMed1987

Phytochrome Regulation of the Response to Exogenous Gibberellins by Epicotyls of Vigna sinensis.

The elongation rate of cowpea epicotyls from whole cowpea (Vigna sinensis) seedlings and derooted and debladed plants (explants) increased after the main light period (8-hour duration) was extended with either continuous low intensity tungsten light or brief (5 minutes) far-red (FR) irradiation. This end-of-day FR effect was reversed by red (R) irradiation suggesting the involvement of phytochrome. These results confirm and extend those obtained previously with other species. Localization studies indicate the epicotyl to be the site of the photoreceptor. Treatment of cowpea seedlings with paclobutrazol, a gibberellin (GA) biosynthetic inhibitor, abolished the FR promoted epicotyl elongation, indicating a role for GAs in this process. There was no significant difference in epicotyl elongation rates of R plus FR irradiated explants treated with GA(1) or GA(20) and R irradiated explants treated with GA(1). However, R irradiation inhibited subsequent epicotyl elongation of GA(20) treated explants. Moreover, the observation, using GC-MS, that GA(1) and GA(20) are native GAs in cowpea lends support to the concept that phytochrome may control the conversion of endogenous GA(20) to GA(1) in cowpea.

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PubMed1987

Partial purification of gibberellin oxidases from spinach leaves.

Four enzyme activities catalyzing the following oxidative steps in the gibberellin (GA) biosynthetic pathway have been extracted from spinach (Spinacia oleracea L.) leaves after exposure to 8 long days: GA(12) --> GA(53) --> GA(44) --> GA(19) --> GA(20). Two of these, GA(53) oxidase and GA(19) oxidase, were separable from the other two, GA(44) oxidase and GA(12) 13-hydroxylase, by anion exchange high performance liquid chromatography (HPLC). Apparent molecular weights of the four enzymes as determined by gel filtration HPLC are: GA(12) 13-hydroxylase, 28,400; GA(53) oxidase, 42,500; GA(44) oxidase, 38,100; GA(19) oxidase, 39,500. GA(44) oxidase was purified approximately 100-fold in 0.3% yield by a combination of ammonium sulfate fractionation, anion exchange HPLC, phenyl-Sepharose chromatography and gel filtration HPLC.

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PubMed1987

In Vitro Gibberellin A(1) Binding in Zea mays L.

The first and second leaf sheaths of Zea mays L. cv Golden Jubilee were extracted and the extract centrifuged at 100,000g to yield a supernatant or cytosol fraction. Binding of [(3)H]gibberellin A(1) (GA(1)) to a soluble macromolecular component present in the cytosol was demonstrated at 4 degrees C by Sephadex G-200 chromatography. The binding component was of high molecular weight (HMW) and greater than 500 kilodaltons. The HMW component was shown to be a protein and the (3)H-activity bound to this protein was largely [(3)H]GA(1) and not a metabolite. Binding was pH sensitive but only a small percentage (20%) appeared to be exchangeable on addition of unlabeled GA(1). Both biologically active and inactive GAs and non-GAs were able to inhibit GA(1) binding. [(3)H]GA(1) binding to an intermediate molecular weight (IMW) fraction (40-100 kilodaltons) was also detected, provided cytosol was first desalted using Sephadex G-200 chromatography. Gel filtration studies suggest that the HMW binding component is an aggregate derived from the IMW fraction. The HMW binding fraction can be separated into two components using anion exchange chromatography.

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PubMed1988

Identification of endogenous gibberellins in navel orange shoots.

Eight gibberellins (GAs) were identified from vegetative shoots of navel orange trees (Citrus sinensis L. Osbeck cv Washington) after sequential purification by reverse-phase C(18) high performance liquid chromatography, Nucleosil 5N(CH(3))(2) high performance liquid chromatography, and capillary gas chromatography-mass spectrometry. GA(1), GA(17), GA(19), GA(20), GA(29), and iso-GA(3) were identified based on the full scan mass spectra and Kovats retention indices. GA(8) was tentatively identified based on the comparison of the full scan mass spectra with the published spectra. GA(44) was tentatively identified from the characteristic masses at the correct Kovats retention index.

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PubMed1989

Endogenous Gibberellins and Shoot Growth and Development in Brassica napus.

Greenhouse-grown oilseed rape (Brassica napus, annual Canola variety ;Westar') plants were harvested at six dates from the vegetative phase until the early pod (silique)-fill/late flowering stage. Endogenous gibberellin (GA)-like substances were extracted from stems, purified, and chromatographed on silica gel partition columns prior to bioassay in serial dilution using the ;Tan-ginbozu' dwarf rice microdrop assay. The concentrations of total endogenous GA-like substances were low during vegetative stages (1 nanogram GA(3) equivalents/gram dry weight), and rose 300-fold by the time of floral initiation. After floral initiation the concentration of GA-like substances fell, then rose again during bolting to maximal levels during the early pod-fill stage (940 nanograms per gram dry weight). The qualitative profiles of GA-like substances varied across harvests, with higher proportions of a GA(1)-like substance at the early pod-fill stage. In a second study stems were similarly harvested at eight dates and the concentrations of endogenous GA(1), the principal bioactive native GA of oilseed rape, were determined by gas chromatography-selected ion monitoring using [17,17-(2)H]GA(1) as a quantitative internal standard. The concentration of GA(1) increased at about the time of floral initiation and then subsequently fell, thus confirming the pattern noted above for total GA-like substances. The exogenous application of paclobutrazol (PP333), a persistent triazole plant growth regulator (PGR) which blocks GA biosynthesis, or another triazole, triapenthenol (RSW0411), prevented flowering as well as bolting; plants remained at the vegetative rosette stage. These results imply a causal role for endogenous GA, in the control of bolting, which normally precedes anthesis. Further, the rise in the concentration of total endogenous GA-like substances, including GA(1), which was associated with floral initiation, and the prevention of visable floral development by the triazole PGRs, also indicates a role for endogenous GAs in the regulation of flowering in B. napus.

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PubMed1989

A Gibberellin-Deficient Brassica Mutant-rosette.

A single-gene mutant (rosette [ros/ros]) in which shoot growth and development are inhibited was identified from a rapid cycling line of Brassica rapa (syn campestris). Relative to normal plants, the mutant germinated slowly, had delayed or incomplete floral development, and reduced leaf, petiole, and internode growth. The exogenous application of GA(3) by foliar spray or directly to the shoot tip of rosette resulted in rapid flowering, bolting (shoot elongation), and viable seed production. Shoots of rosette contained endogenous levels of total gibberellin (GA)-like substances (;Tan-ginbozu' dwarf rice assay) of about one-tenth of that of the normal rapid-cycling line of B. rapa which consisted almost entirely of a very nonpolar, GA-like substance which yielded GA(1) and GA(3) upon mild acid hydrolysis. In a normal rapid-cycling B. rapa line, the nonpolar putative GA(1) and GA(3) conjugates were present, but additionally, free GA(1) and GA(3) were abundant and identified by gas chromatography-mass spectrometry-selected ion monitoring. The quantities of free GA(1) and GA(3) in the normal line and in rosette were quantified by GC-MS-SIM using [(2)H(2)]GA(1) as an internal standard. Fourteen-day-old rosette and normal seedlings contained 5.3 and 23.2 ng GA(1) per plant, respectively. At day 21 the rosette plants contained 7.7 and 26.1 nanograms per plant of GA(1) and GA(3), while normal plants contained 31.1 and 251.5 nanograms per plant, respectively. Thus, normal plants contained from four to ten times higher levels of total GA-like substances, GA(1), or GA(3), than rosette. The ros allele results in reduced GA level, yielding the rosette phenotype whose delayed germination and flowering, and reduced shoot growth responses indicate a probable role for endogenous GA(1) and GA(3) in the regulation of these processes in Brassica.

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PubMed1989

Immunoaffinity techniques applied to the purification of gibberellins from plant extracts.

The use of immunoaffinity columns containing anti-gibberellin (GA) antibodies for the selective purification of GAs in plant extracts is described. GA(1), GA(3), GA(4), GA(5), GA(7), and GA(9) conjugates to bovine serum albumin were synthesized and used to elicit anti-GA polyclonal antibodies (Abs) in rabbits. Protein A purified rabbit serum, containing a mixture of anti-GA Abs, was immobilized on matrices of Affi-gel 10 or Fast-Flow Sepharose 4B. Columns of these immunosorbents retained a wide range of C-19 GA methyl esters, but no C-20 GA methyl esters. Quantitative recovery of C-19 GA methyl esters was achieved from the columns, which, after reequilibration in buffer, could be reused up to 500 times. The immunosorbents were tested by examination of extracts from immature soybean and pea seeds. GAs were initially purified by passing the extracts through DEAE-cellulose and concentrating them on octadecylsilica. The extracts were methylated and further purified on the mixed anti-GA immunoaffinity columns. GAs were detected and quantified as methyl esters or methyl ester trimethylsilyl ethers by gas chromatography-mass spectrometry-selected ion monitoring. GA(7) was found in soybean seeds, 17 days after anthesis, at low levels (8.8 nanograms per gram fresh weight). C-19 GAs were examined in cotyledons, embryonic axes, and testae of G2 pea seeds harvested 20 days after anthesis. High levels of GA(20) and GA(29) were found in cotyledons (3580 and 310 nanograms per gram fresh weight, respectively) and embryonic axes (5375 and 1430 nanograms per gram) fresh weight, respectively). Lower levels of GA(9) were found in cotyledons and embryonic axes (147 and 161 nanograms per gram fresh weight, respectively). GA(9) was the major GA of testae at levels of 195 nanograms per gram fresh weight. Trace quantities of GA(20) and GA(51) were also observed in testae.

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