Analysis of native gibberellins in the internode, nodes, leaves, and inflorescence of developing Avena plants

The native gibberellins (GAs) of various organs of the Avena plant were analyzed by bioassay and gas chromatography-mass spectrometry (GC-MS) after silicic acid partition column chromatography. The major GA of the inflorescence was identified as GA₃ by GC-MS, and this GA also forms the major component of the nodes, p-1 internode, and roots as determined by GLC or chromatography/bioassay. The inflorescence and nodes are the major sources of native GAs, the last two leaves, internode, and roots having significantly lower amounts of GA-like substances. In the internode, less polar GAs predominated at the lag stage of development, whereas by the log and plateau stages, the more polar GAs increased significantly.     

Photoperiod-induced changes in gibberellin metabolism in relation to apical growth and senescence in genetic lines of peas (Pisum sativum L.)

In an early-flowering line of pea (G2) apical senescence occurs only in long days (LD), while growth in short days (SD) is indeterminate. In SD, G2 plants are known to produce a graft-transmissible substance which delays apical senescence in related lines that are photoperiod-insensitive with regard to apical senescence. Gibberellic acid (GA₃) applied to the apical bud of G2 plants in LD delayed apical senescence indefinitely, while N⁶-benzyladenine and -naphthaleneacetic acid were ineffective. Of the gibberellins native to pea, GA₉ had no effect whereas GA₂₀ had a moderate senescence-delaying effect. [³H]GA₉ metabolism in intact leaves of G2 plants was inhibited by LD and was restored by placing the plants back in SD. Leaves of photoperiod-insensitive lines (I-types) metabolized GA₉ readily regardless of photoperiod, but the metabolites differed qualitatively from those in G2 leaves. A polar GA₉ metabolite, GA_E, was found only in G2 plants in SD. The level of GA-like substances in methanol extracts from G2 plants dropped about 10-fold after the plants were moved from SD to LD; it was restored by transferring the plants back to SD. A polar zone of these GA-like materials co-chromatographed with GA_E. It is suggested that a polar gibberellin is synthesized by G2 plants in SD; this gibberellin promotes shoot growth and meristematic activity in the shoot apex, preventing senescence.Abbreviations GA gibberellin - GA₃ gibberellic acid - SD short days - LD long days     

Gibberellin-induced delay of leaf senescence of Alstroemeria cut flowering stems is not caused by an increase in the endogenous cytokinin content

The effects of various chemically pure gibberellins and cytokinins on leaf yellowing of Alstroemeria were described. The loss of chlorophyll was measured both in leaves of cut flowering stems and in a model system consisting of detached leaf tips. It was demonstrated that plant growth substances affected chlorophyll loss in both systems to the same extent. Leaf senescence was delayed by various gibberellins and cytokinins. The results demonstrated that some of the gibberellins (GA₄ and GA₇) are far more effective in delaying chlorophyll loss than GA₃, which is commonly used as a postharvest treatment for Alstroemeria cut flowering stems. Immunoassays were used to demonstrate that the effect of gibberellins on leaf yellowing does not involve an increase in the endogenous cytokinin concentrations in the leaves as an intermediate step.Abbreviations GA gibberellin A - HPLC high performance liquid chromatography - GA_3Mc GA₃-methyl ester - ZR zeatin riboside - IPAR isopentenyl adenine riboside.     

Interaction of growth retardants,daylength, and gibberellins A19, A20, and A1 on shoot elongation in birch and alder

Gibberellins A₁₉, A₂₀, and A₁ were applied to seedlings of birch (Betula pubescens Ehrh.) and alder (Alnus glutinosa (L.) Gaertn.) in order to test their ability to counteract growth inhibition induced by growth retardants (ancymidol and BX-112) or short day (SD, 12 h) photoperiod. Ancymidol inhibits early and BX-112 inhibits late steps in gibberellin biosynthesis. BX-112 inhibited stem elongation in both species while ancymidol, applied as a soil drench, was effective in alder only. Growth retardants affected stem elongation mainly by inhibiting elongation of internodes. All three gibberellins were equally active when applied to seedlings treated with ancymidol; however, only GA₁ was able to counteract the growth inhibition induced by BX-112. SD-induced cessation of elongation growth in birch was counteracted by GA₁, and to some degree, by GA₂₀, while GA₁₉ was inactive. SD treatment did not induce cessation of apical growth in alder. These results are consistent with the hypothesis that of gibberellins belonging to the early C-13 hydroxylation pathway, GA₁ is the only active gibberellin for stem elongation.     

Effect of Different Gibberellins on the Growth of the Hypocotyl

It has been stated earlier that hypocotyls of different plants show different growth response to added GA₃. It was suggested that this difference may be due to the requirement of some specific gibberellin. Hence hypocotyl growth response of three groups of plants has been studied with different gibberellins: group one showing no or insignificant growth response, group two showing 150–200 per cent growth response and group three showing 300–500 per cent growth response to added GA₃. Eight gibberellins were used, viz., GA₁, GA₂, GA₃, GA₄, GA₅, GA₇, GA₈ and GA₉, to test if this varying response is connected with the requirement of some specific gibberellin. In general, the results obtained do not favour this view. Iberis amara, a plant showing no response to added GA₃, Dianthus sp., a plant showing 150 to 200 per cent response and Lactuca satwa, Antirrhinum majus and Nicotiana tabacum, plants showing 300 to 500 per cent response, were promoted by all the gibberellins tested to a similar extent as by GA₃, with the exception of GA₈ which was inactive in most of the cases.     

Gibberellins and Light Regulated Petiole Growth in Thlaspi arvense L

Petiole growth in Thlaspi arvense L. was stimulated when a basic 8 hour photoperiod (4.20 milliwatts per square centimeter) was extended with low intensity light (0.16 milliwatt per square centimeter) from incandescent lamps. The day length extension was effective only when the light contained high proportions of far red light. Exogenous gibberellin A₃ (GA₃) could partially substitute for the promotive effect of the extended photoperiod. Moreover, the GA biosynthesis inhibitor 2-chlorocholine chloride inhibited the increase in petiole growth induced by the extended photoperiod. However, evidence was obtained indicating that gibberellins do not mediate the effect of the extended photoperiod. First, petiole growth was greater in plants receiving both exogenous GA₃ and a day length extension than the sum of the effects of the two treatments alone. Second, petioles were sensitive to exogenous GA₃ only during the early stages of leaf development, whereas mature (but not senescent) leaves continued to respond to an extension of the photoperiod. Third, the cellular basis for growth induced by extending the photoperiod was different from that observed with GA₃. It was concluded that light and gibberellins are both important in the overall regulation of petiole growth, but act through independent mechanisms.     

The Relationship between Levels of Endogenous Gibberellins and the Response of Vigna Hypocotyls to Exogenous Indole-3-Acetic Acid

Segments excised from the upper and the lower parts of cowpea(Vigna unguiculata L.) hypocotyls were compared in terms oftheir responses to exogenous indole-3-acetic acid (IAA) in relationto their endogenous levels of gibberellin. Growth of the segmentswas measured continuously during xylem perfusion with a lineardifferential transformer. IAA induced a burst of elongationin the upper segments but only slight promotion of growth inthe lower segments. Treatment with uniconazole, a potent inhibitorof the biosynthesis of gibberellins, reduced the responsivenessof the upper segments to exogenous IAA to about one half ofthe control value. Pre-perfusion with GA₃ of such segments fortwo hours prior to application of IAA, partially restored theresponsiveness to IAA. Analysis by GC/MS identified GA₁, GA₄,GA₉ GA₂₀ and GA₅₁ as native gibberellins in the hypocotyls ofcowpea seedlings. Analysis by GC/SIM also showed that the physiologicallyactive gibberellins (GA₁ and GA₄) were located mainly in theupper part of the hypocotyl and the treatment with uniconazolemarketly reduced the endogenous level of gibberellins thereto less than 11% of the control level. These results suggestthat levels of endogenous gibberellins possibly control theresponse to IAA in these segments. (Received May 12, 1994; Accepted November 15, 1994)     

The Interaction of Plant Growth Regulators and Vernalization on the Growth and Flowering of Cauliflower (Brassica oleracea var. botrytis)

The growth and flowering response of a cold-requiring cauliflower (Brassica oleracea var. botrytis cv. 60 day) to a range of temperatures under 10 h photoperiod and to growth regulator application were investigated. Endogenous gibberellin A₁(GA₁) concentrations were also assessed under these treatments. Flowering and growth of the inflorescence stalk were correlated with plant developmental stage at the time of a vernalizing cold treatment. Temperature and its duration also affected flowering and inflorescence development. The most effective temperature for inflorescence induction was 10 °C. Flowering did not occur in non-vernalized plants (25 °C) even though they had been treated with GA₃. Application of GA₃ promoted inflorescence stalk elongation greatly in vernalized plants (10 °C), but less so in partially vernalized plants (15 °C or 20 °C). Paclobutrazol (PP₃₃₃) sprayed at the 8–9 leaf stage significantly suppressed inflorescence stalk length and slightly delayed flower bud formation and anthesis. Vernalization at 10 °C increased endogenous GA₁ content in both leaves and the inflorescence stalk irrespective of GA₃ or PP₃₃₃ treatment. Application of GA₃ tended to increase GA₁ levels, while PP₃₃₃ significantly reduce GA₁, both irrespective of vernalization. Vernalization is an important factor for flowering, but not curd formation in this cauliflower cv. 60 day and GA₁ is likely a causal factor in inflorescence stalk elongation.     

ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non‐structural carbohydrates in leaves,enhancement of phloem area and expression of sugar transporters

Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A₃ (GA₃) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot‐grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA₃ solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre‐veraison, full veraison and post‐veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA‐treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA₃ increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA₃ to berries and stems, respectively, was due to build‐up of non‐structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.     

In vitro glucosylation of gibberellins

In maturing fruits ofPhaseolus coccineus a soluble glucosyltransferase activity occurs which converts gibberellins into their O-glucosides. The enzyme glucosylates GA₃ and structurally closely related gibberellins (GA₇ and GA₃₀) to their 3-O-glucosides by transfer of glucose preferentially from UDP-glucose. From cell suspension cultures ofLycopersicon peruvianum cytosolic glucosyltransferases were isolated which in the presence of UDP-glucose converted GA₇ and GA₉ to the corresponding glucosyl esters. In both cases numerous other gibberellins failed to serve as substrates. Thus, the enzymes are UDP-glucose: gibberellin glucosyltransferases of considerable substrate specificity.     

Enhancement of Gibberellin Activity by Ethylenediaminetetraacetic Acid in Celery Seeds and Embryoless Barley Seeds

The phytochrome-controlled dormancy of celery seeds (Apium graveolens L.) can be broken by exogenously applied growth regulators. Gibberellins, especially the mixture of GA₄ and GA₇ appeared to be the primary stimuli for germination of darkincubated seeds. However, concentrations less than 1 mM were ineffective in replacing the light requirement in one celery cultivar (cv.Utah), and in another cultivar (cv.Lathom Blanching), concentrations above 1 mM were insufficient. The addition of ethylenediaminetetraacetic acid (EDTA) to gibberellins, increased markedly their activity and reduced by several orders of magnitude the gibberellin concentrations needed to stimulate a light treatment. This synergistic activity is similar to the effect of benzyladenine (BA) or Succinic acid-2,2-dimethylhydrazide (SADH) when added to gibberellins. In a diverse plant system, the mixture of gibberellin with EDTA increased significantly the amount of reducing sugars released by embryoless barley seeds.     

The Biotechnology of Bacillus Thuringiensis

Abstract

Gibberellins are a classic example of the production of plant growth regulators by microorganisms. They are important biotechnological products and are increasingly used in agriculture and horticulture.

This article intends to assemble information on the history of the identification of gibberellins (GA) and producing microorganisms, especially Gibberella fujikuroi (Saw.) Wr. Furthermore, the biosynthesis of gibberelins through the isoprenoid biosynthetic pathway will be described. The main product of GA biosynthesis in Gibberella fujikuroi is gibberellic acid (GA₃), which is formed from GA₄ via GA₇. Both the amount and the type of gibberellins produced by the fungus are dependent on the genetic constitution of the strain and the fermentation conditions.

Mutation and selection for increased product formation are probably the most important factors in improving the yield of gibberellins. Some publications concerning methods of parasexual recombination will also be summarized. Beside strain improvement of wild strains, medium development and appropriate cultivation techniques (batch, fed-batch-, continuous-, and solid state-fermentation) are very important prerequisites for successful economy of gibberellin production. Furthermore, the most important ways of gibberellin recovery and purification are described. Continuing reductions in the costs make gibberellins more attractive for existing applications and open possibilities for further applications of GA₃ and some other active gibberellins like GA₄, Ga₇, and GA₉     

Gibberellins in developing fruits of Pisum sativum cv. Alaska: Studies on their role in pod growth and seed development

Gibberellins A₁, A₈, A₂₀ and A₂₉ were identified by capillary gas chromatography-mass spectrometry in the pods and seeds from 5-d-old pollinated ovaries of pea (Pisum sativum cv. Alaska). These gibberellins were also identified in 4-d-old non-developing, parthenocarpic and pollinated ovaries. The level of gibberellin A₁ within these ovary types was correlated with pod size. Gibberellin A₁, applied to emasculated ovaries cultured in vitro, was three to five times more active than gibberellin A₂₀. Using pollinated ovary explants cultured in vitro, the effects of inhibitors of gibberellin biosynthesis on pod growth and seed development were examined. The inhibitors retarded pod growth during the first 7 d after anthesis, and this inhibition was reversed by simultaneous application of gibberellin A₃. In contrast, the inhibitors, when supplied to 4-d-old pollinated ovaries for 16 d, had little effect on seed fresh weight although they reduced the levels of endogenous gibberellins A₂₀ and A₂₉ in the enlarging seeds to almost zero. Paclobutrazol, which was one of the inhibitors used, is xylem-mobile and it efficiently reduced the level of seed gibberellins without being taken up into the seed. In intact fruits the pod may therefore be a source of precursors for gibberellin biosynthesis in the seed. Overall, the results indicate that gibberellin A₁, present in parthenocarpic and pollinated fruits early in development, regulates pod growth. In contrast the high levels of gibberellins A₂₀ and A₂₉, which accumulate during seed enlargement, appear to be unnecessary for normal seed development or for subsequent germination.Abbreviations GA_(a) gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - PFK perfluorokerosene - PVP polyvinylpyrrolidone     

Interactions between Abscisic Acid, Gibberellins and Cytokinins in Grand Rapids Lettuce Seeds Germination

Experiments with Grand Rapids lettuce seeds (Lactuca sativa L.) maintained in darkness or irradiated with red light have shown that the inhibition of germination induced by low concentrations of ABA (2, 4, 6 μM) could be overcome by gibberellins (GA₃ or GA₄). The same results were obtained, although to a lesser extent, under the influence of two out of the four cytokinins tested (K and BAP) for seeds maintained in darkness. To suppress the block induced by higher concentrations of ABA (for example 8 μM), it was necessary to apply a cytokinin (K, BAP, Z or 2iP) and a gibberellin (GA₄ or GA₃) simultaneously, or a cytokinin following a red light treatment. Experiments conducted in darkness in which ABA (8 μM) was applied together with a cytokinin (BAP) and a gibberellin (GA₄) showed that the gibberellin and the cytokinin played similar roles towards each other and towards ABA.     

Promotory effect of GA13 on flowering ofAmaranthus — a short day plant

Abstact The three plant types ofAmaranthus namely,A. caudatus f.albiflorus, A. caudatus f.caudatus andA. tricolor var.tristis are qualitative short day plants with critical photoperiods 16.0, 15.5 and 15.0 h, respectively. Gibberellins A₃, A₄₊₇ and A₁₃ affect extension growth, leaf differentiation and floral induction differently. Thus, in all the three plant types ofAmaranthus, whereas, GA₃ and G₄₊₇ enhanced extension growth, GA₁₃ was completely ineffective under both, 24- and 8-h photoperiods. None of the three gibberellins could affect the leaf differentiation. In all the three plant types, flowering was promoted by GA₁₃ and not by other gibberellins tried. GA₁₃ caused promotion was manifested in two manners, firstly by lowering the critical dark period requirement in each inductive cycle, and secondly by shortening the total period taken for the initiation of inflorescence primordia under inductive photoperiods. The floral induction by gibberellins inAmaranthus is contrary to the gibberellin-anthesin concept of Chailakhyan. It is suggested that gibberellins other than GA₃ may be playing an important role in floral morphogenesis of short day plants.     

The levels of GA3 and GA20 may be associated with dormancy release in Onopordum nervosum seeds

Endogenous levels of two gibberellins, GA₃ andGA₂₀, were quantified in unimbibed Onopordumnervosum seeds collected from two different populations, whichshoweddifferences in their germination capacity. After purifying the seed extracts,gibberellin levels were evaluated by gas chromatography mass spectrometry byusing selected ion monitoring (GC-MS-SIM) adding deuterated gibberellins asinternal standards. The intraspecific differences in germination capacity wereassociated with differences in the endogenous levels of both gibberellins. Thecontents of GA₃ and GA₂₀ in seeds with high germinationrate were twice and five times higher, respectively, than those from seeds witha low germination rate, indicating a possible role of gibberellins in dormancyrelease in this plant species.     

Endogenous gibberellins in clover broomrape,a parasitic plant,and its host,clover: Dependency of the parasite on the host for gibberellin production

Endogenous gibberellins were analyzed from a parasitic plant, clover broomrape (Orobanche minor Smith), and its host, clover (Trifolium repens L.). Members of both the early-13- and the early-non-hydroxylation pathways were identified from both the parasite and the host (GA₁₂, GA₂₄, GA₉ GA₄, GA₄₄, GA₁₉, GA₂₀, and GA₁ from clover broomrape; GA₉, GA₄, GA₄₄, GA₁₉, GA₂₀, and GA₁ from clover). Quantitative analyses showed that GA₄₄ was present at high levels in both host and parasite. The similarity in the gibberellins suggests the possibility that the major gibberellins in clover broomrape are transported from clover. However gibberellins such as GA₅₈, GA₃₈, and notably GA₄₇ which was identified from a plant for the first time were detected only from clover broomrape, suggesting that the parasite may have the ability to produce at least those gibberellins     

Identification of gibberellin A1 in the embryo suspensor of Phaseolus coccineus

By combined gas chromatography-mass spectrometry the gibberellin present in suspensors of heart-shaped embryos of Phaseolus coccineus has been identified as Gibberellin A₁ (GA₁). The amount of GA₁ in 2000 suspensors (452 mg), as estimated by gas chromatography. was 4g. The presence of GA₁ in suspensors of P. coccineus is discussed in relation to our present knowledge of the occurrence of many gibberellins in developing seeds and immature fruits of the same species.Abbreviations FID flame ionization detector - GA gibberellin - GC gas chromatography - MS mass spectrometry - PGC preparative gas chromatography - Stage A heart-shaped embryo - Stage B cotytedonary embryo - TMS trimethylsilyl     

Isolation and Characterization of Gibberellins in Calonyction aculeatum and Structures of Gibberellins A30, A31, A33 and A34

Four novel gibberellins GA₃₀, GA₃₁, GA₃₃, GA₃₄, five known gibberellins GA₈, GA₁₇ (free acid and its monomethyl ester), GA₁₉, GA₂₇, GA₂₉ and the gibberellin-like substances were isolated from immature seeds of evening-glory (Calonyction aculeatum). The structures of GA₃₀, GA₃₁, GA₃₃ and GA₃₄ were elucidated as IX, XVIII, XXII and XXXIV, respectively. The three gibberellin-like substances were partially characterized.     

Effect of nine different gibberellins on stem elongation and flower formation in cold-requiring and photoperiodic plants grown under non-inductive conditions

Summary The effect of gibberellins A₁ through A₉ on stem elongation and flower formation in five plants was tested. The plants wereMyosotis alpestris and a biennial strain ofCentaurium minus (cold-requiring plants),Silene armeria andCrepis parviflora (long-day plants), andBryophyllum crenatum (a long-short-day plant). The two former plants were maintained on non-inductive temperatures and long days, the three latter on short days, InMyosotis, flower formation was only obtained with GA₇ and GA₁, the latter being relatively less active. InCentaurium GA₃ was the most effective, followed by GA₁, GA₄ and GA₇ and perhaps GA₅ and GA₉. InSilene, flower formations was induced only by GA₇. InCrepis, the most effective gibberellins were GA₄ and GA₇, inBryophyllum, GA₃, GA₄ and GA₇. Thus, the different gibberellins exhibited considerable differences in their activity with respect to flower induction, and different plants exhibited in this respect certain specific differences in their sensitivity to the various gibberellins. Except inCrepis, flower initiation as a result of gibberellin treatment was always preceded by substantial stem or internode elongation; however, the correlation between the effect of the different gibberellins on stem elongation and flower induction was not in all cases complete. No correlation of the flower-inducing and elongation-promoting activity with the chemical structure of the different gibberellins could be recognized.With 2 Figures in the TextWork in part supported by the National Science Foundation, grants G-16408 and G-17483.