Formation of bound gibberellins inPharbitis nil

Advancing Glucose Conjugated Gibberellins Discovery: A Structure-Oriented Screening and Identification Method for Unraveling Gibberellin Metabolites in Plants

Gibberellins (GAs) play a pivotal role in modulating plant growth and development. Glucose-conjugated gibberellins (Glc-GAs), a prevalent conjugated form of GAs, regulate intracellular GA levels by the coupling and decoupling of glucose groups. However, the diversity of Glc-GAs identified within individual species remains limited, hinting at a multitude of yet undiscovered gibberellin metabolites. This lacuna poses considerable impediments to research efforts dedicated to comprehensively delineating the GA metabolic pathway. In this study, we developed a structure-oriented screening and identification method for Glc-GAs in plant species by employing LC-MS/MS coupled with chemical derivatization. Through the application of chemical derivatization technique, carboxyl groups on Glc-GAs were labeled which effectively enhanced the sensitivity and selectivity of mass spectrometry detection for these compounds. Concurrently, the integration of mass spectrometry fragmentation and chromatographic retention behavior facilitated the efficient screening and identification of potential Glc-GAs. With this strategy, we screened and identified 12 potential Glc-GAs from six plant species. These findings expand the Glc-GA diversity in plants and contribute to understanding GA metabolic pathways.

Influence of photoperiod on seed development in the genetic line of peas G2 and its relation to changes in endogenous gibberellins measured by combined gas chromatography - Mass spectrometry

When apical senescence in the genetic line of peas G2 was prevented by short days fruit development was also found to be retarded. The levels of GA20 and GA29 in cotyledons and pods grown under long or short days were measured by gas chromatography - mass spectrometry multiple ion monitoring using extracts derivatised with deuterated trimethylsilyl groups as internal standards. The levels of GA20 but not GA29, were increased by short days. Conventional gas chromatography - mass spectrometry showed that relative to GA29 the levels of GA19, the other GA identified in G2 cotyledons, were also increased in short days. The levels of GA20 in the pods were highest during the main phase of pod growth early in fruit development.

The diffusion of gibberellins into agar and water during early germination of Pharbitis nil Choisy

Agar diffusion of imbibed seeds yielded significant amounts of diffusible Gibberellin-like substances. An analysis of the extractable and diffusible gibberellin-like substance, including an analysis of the remaining imbibition water of the seeds, indicated that a significant part of these gibberellin-like substances could be attributed to a net biosynthesis of these substances in the imbibing seeds. At the same time it was found that water diffusion yielded considerably more gibberellin-like activities than comparable agar diffusions i.e. 10 to 12 fold in general.Agar as well as water diffusion showed a temperature effect with regard to the yield of gibberellin-like substances particularly during the first 6 h of diffusion. The yield of these substances is lower at 10°C, and remains lower as shown with consecutive diffusions, in comparison with the yields at 20°C or 30°C.With both agar and water diffusion the sum of activities obtained with consecutive diffusions is always higher, often considerably higher, than equal periods of continuous diffusion which is probably due to inactivation and/or interference of inhibitory substances with the bioassay responses. Finally, water diffusates of both seeds and seedlings of the normal growing cv. Violet of Japanese morning glory contained considerably more gibberellin-like activities than those of the dwarf cv. Kidachi which indicated that normals synthesize more gibberellins than dwarfs.

The metabolism of applied gibberellic acid in Pharbitis nil choisy: tentative identification of its sole metabolite as gibberellic acid glucoside and some of its properties

Radioactive gibberellic acid ([(14)C]GA3) applied to seedlings of Pharbitis nil strain Violet is converted to one single metabolite (R-[(14)C]GA3), which has been tentatively identified as GA3-glucoside. As with authentic GA3-glucoside, R-[(14)C]GA3 can be hydrolysed to some extent with cellulase and β-glucuronidase, but hardly at all with β-glucosidase. Acid hydrolysis, which is more effective than enzymatic hydrolysis, yielded GA3 as well as a biological inactive compound. The latter represents a degradation product of GA3 due to the sensitivity of GA3 to acidic conditions.The R-[(14)C]GA3, like authentic GA3-glucoside, possesses little or no biological activity. R-[(14)C]GA3 applied to developing seeds is partly hydrolysed during imbibition of the mature seed but is, however, reconverted to R-[(14)C]GA3 during subsequent germination. Applied R-[(14)C]GA3 is strongly accumulated in the cotyledons of Pharbitis seedlings, to a greater extent than [(14)C]GA3. However, unlike [(14)C]GA3 it is not accumulated in the apical regions of the hypocotyl. Furthermore no competition was observed between R-[(14)C]GA3 and [(14)C]GA3, which suggests that they do not compete for the same sites.

Growth regulator levels in embryo and suspensor of Phaseolus coccineus at two stages of development

Gibberellins and auxins were extracted from embryos and suspensors of Phaseolus coccineus L. at two stages of development: A) heart-shaped embryo and B) cotyledonary embryo with suspensor in the initial stage of degeneration. The time interval between the two stages was 5-6 days.In both embryos and suspensors, gibberellin (GA)-like activity was found in three fractions: F-1 (ethyl acetate fraction at pH 8.0), F-2 (free GAs) and F-3 (bound GAs). At stage A, the total GA activity in the suspensor was about 30 times greater than in the embryo and the bound GAs contributed by about 90% to the total GA content. A dramatic decrease in level of bound GA-like substances was found in suspensors at stage B, when the level of total GAs in the embryo had increased to 10 times that at stage A. This might suggest a transport of GAs from the suspensor to the embryo. In both embryo and suspensor, qualitative changes in GAs with shift in activity of the fractions tested occurred at the two developmental stages.The methanolic extracts of stage A suspensors showed two inhibitors, one much more active than the other, and two large peaks of growth promoting activity at Rf 0.4-0.7; in stage A embryos, the general activity of the extracts was lower and the promoting effect was spread over Rf 0.3-0.9.The present results seem to support the view that the suspensor plays a role in embryogenesis by acting as a site of synthesis of growth regulators needed by the embryo.

The conversion of gibberellin A1 to gibberellin A 8 by a cell-free enzyme system

An enzyme system which catalyzes hydroxylation of (3)[H]gibberellin A1 ([(3)H]GA1) to [(3)H]GA8 was obtained from homogenates of germinating bean (Phaseolus vulgaris L.) seed. The system remained in the supernatant after centrifugation at 95000×g for 2 h. Hydroxylation occurred at one of the specifically (3)H-labeled positions (C-2) and, concomitantly, produced [(3)H]water whic was used to measure formation of [(3)H]GA8. NADPH and/or ascorbate are cofactors utilized by this enzyme. EDTA effectively inhibited the system, suggesting a cation requirement.

The role of gibberellic acid in the hydrolysis of endosperm reserves in Zea mays

Excised maize (Zea mays L.) endosperms incubated in buffer rapidly degrade their starch and protein reserves. These processes are not markedly stimulated by addition of gibberellic acid (GA3). However protease and α-amylase production are strongly inhibited by abscisic acid, and this inhibition can be overcome by exogenous GA3. Endosperms of a dwarf mutant maize (d 5), which is deficient in endogenous GA, produce only small amounts of protease and α-amylase. With these mutants oxogenous GA3 causes a 3-5fold stimulation in hydrolase production. Our interpretation of these results is that in many cases maize endosperms contain sufficient gibberellin to stimulate maximal hydrolase production and starch and protein breakdown.

Interconversion of gibberellin A4 to gibberellins A 1 and A 34 by dwarf rice, cultivar Tan-ginbozu

Interconversion of GA4 to GA1 and GA34 occurred within 24 h of application of 1,2-[(3)H]-GA4 to seedlings of dwarf rice, cv. Tan-ginbozu. Identification was made by direct comparison of the trimethylsilyl ether derivatives of the methyl esters of Silica-gel partition-column fractions on gas-liquid radiochromatography with derivatized GA1 and GA34 standards on three columns: 2% QF-1, 2% SE-30, and 1% XE-60. GA2, an artifact of the purification and chromatography system, may also be formed by the plant. The conversions from GA4 to GA1 and GA34 are single hydroxylations. At least two unidentified radioactive products were also formed by the plant. Interconversions were in the order of 0.3 to 0.8% of applied [(3)H]-GA4.