Biological evaluation of 5-substituted pyrimidine derivatives as inhibitors of brassinosteroid biosynthesis

A series of 5-substituted pyrimidine derivatives was synthesized, and their ability to inhibit brassinosteroid biosynthesis was tested. The biological activity of these compounds was evaluated by the cress stem elongation method. Among the synthesized compounds, alpha-(4-chlorophenyl)-alpha-phenyl-5-pyrimidinemethanol (DPPM 4) exhibited potent inhibitory activity for retarding cress stem elongation in the light. This inhibition was reversed by the application of 10 nM brassinolide, but not by 1 microM GA3. DPPM 4 also affected Arabidopsis growth in the dark. DPPM 4-treated Arabidopsis had phenotypes like those of brassinosteroid-deficient mutants, with short hypocotyls and open cotyledons, in the dark. These biological changes were restored by the co-application of 10 nM brassinolide, but not by 1 microM GA3, suggesting that the primary site of action of DPPM 4 was the brassinosteroid biosynthetic pathway.

Expression pattern of the CsPK3 auxin-responsive protein kinase gene

We have previously cloned a cDNA of a putative serine/threonine protein kinase gene named CsPK3 from cucumber, the mRNA level of which was up-regulated by auxin and down-regulated by light irradiation. To examine the CsPK3 gene expression in detail, we cloned a genomic DNA of CsPK3 gene and made transgenic tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) plants containing the fused CsPK3 promoter-beta-glucuronidase gene. The beta-glucuronidase expression was detected in the shoot apex, vascular tissues, and the outermost layer of cortex. The histological distribution of CsPK3 mRNA in cucumber seedlings was supported by in situ hybridization, where the positive signals were observed in similar tissues as those observed by beta-glucuronidase staining. The responsiveness of the CsPK3 gene to auxin and light was also confirmed for beta-glucuronidase activity. The pattern of beta-glucuronidase staining changed during the development of the tobacco seedlings. The results of our experiment showed that CsPK3 was expressed in a wide variety of tissues and cells in which the developmental and growth controls by auxin are suggested.

A novel transposon tagging element for obtaining gain-of-function mutants based on a self-stabilizing Ac derivative

A novel tagging system AcREH, designed for obtaining gain-of-function mutations, was prepared on the basis of a self-stabilizing Ac transposon derivative. The transposable element, DsAT, was constructed in a way that it can activate transcription of neighboring genes by two 35S promoters and/or by four tandem repeats of the enhancer fragment of this promoter. DsAT revealed somatic excision in the first generation of the tobacco transformants. The element exhibited germinal excision to the next generation, as demonstrated by PCR and Southern hybridization analysis. In spite of the structure of the element, which may inhibit the expression of the transposase gene, the frequency of germinal excision was comparable to or higher than those so far reported, suggesting the applicability of the element for gene tagging.

Antiproliferative effects of small fruit juices on several cancer cell lines

Juices prepared from small fruits, mainly growing in the northern part of Japan, were studied in an attempt to explore the feasibility of an assay that screens cytotoxic properties. Screening of 43 small fruit juices indicated that Actinidia polygama Maxim., Rosa rugosa Thunb., Vaccinium smallii A. Gray and Sorbus sambucifolia Roem, strongly inhibited the proliferation of all cancer cell lines examined and yet these juices were substantially less cytotoxic toward normal human cell lines.

Pharbitis class-1 knotted-like homeobox gene, PKn3, shares similar characteristics to those of class-2 knotted-like genes

Three novel homeobox genes, PKn1-3 (Pharbitis knotted-like), were isolated from Japanese morning glory (Pharbitis nil Chois, strain Violet). A sequence analysis showed that these genes belong to the knotted class-1 gene family and that PKn3 has a relatively unique sequence. All PKn genes are expressed in shoot apices, stems and roots, but not in cotyledons. Transformed tobacco with PKn1 or PKn2 displayed leaf shrinkage and a dwarf phenotype, while the ectopic expression of PKn3 gave no altered phenotypes. In situ hybridization showed that PKn3 is up-regulated in developing leaf primordia and that this expression becomes restricted in the basal region of young leaf blades, which is reminiscent of the expression pattern of the class-2 knotted gene, NTH23. These data suggest that these Pharbitis homeobox genes participate in the differentiation in shoots and suggest a unique function of PKn3 in developing leaves.

Differentiation-inducing effects of small fruit juices on HL-60 leukemic cells

Epidemiological studies indicate that high intakes of fruits and vegetables are associated with a reduced risk of cancer, and several plant-derived drugs have been developed in medical oncology. Since only a small part of the flora has been tested for any kind of bioactivity, we chose small fruits as sources of differentiation-inducing activity against HL-60 leukemic cells. We have prepared juices from various small fruits that grow mainly in the northern part of Japan. Screening of 43 samples indicated that juices of Actinidia polygama Maxim., Rosa rugosa Thunb., Vaccinium smallii A. Gray, and Sorbus sambucifolia Roem. strongly induced differentiation of HL-60 cells to monocyte/macrophage characteristics in a concentration-dependent manner as indicated by histochemical and biochemical examinations.

Synthesis and biological activity of 4'-methoxy derivatives of abscisic acid

Replacing the 4'-carbonyl group of abscisic acid with a methoxy group does not affect the abscisic acid (ABA)-like activities of the product in barley aleurone protoplasts, although the reduction of ABA to 4'-hydroxyl derivatives significantly reduces the ABA-like activity of the products. This suggests that methoxy derivatives of abscisic acid might be used to produce probes for ABA binding proteins.

Characterization of brassinazole, a triazole-type brassinosteroid biosynthesis inhibitor

Screening for brassinosteroid (BR) biosynthesis inhibitors was performed to find chemicals that induce dwarfism in Arabidopsis, mutants that resembled BR biosynthesis mutants that can be rescued by BR. Through this screening experiment, the compound brassinazole was selected as the most potent chemical. In dark-grown Arabidopsis, brassinazole-induced morphological changes were nearly restored to those of wild type by treatment with brassinolide. The structure of brassinazole is similar to pacrobutrazol, a gibberellin biosynthesis inhibitor. However, in assays with cress (Lepidium sativum) plants, brassinazole-treated plants did not show recovery after the addition of gibberellin but showed good recovery after the addition of brassinolide. These data demonstrate that brassinazole is a specific BR biosynthesis inhibitor. Brassinazole-treated cress also showed dwarfism, with altered leaf morphology, including the downward curling and dark green color typical of Arabidopsis BR-deficient mutants, and this dwarfism was reversed by the application of 10 nM brassinolide. This result suggests that BRs are essential for plant growth, and that brassinazole can be used to clarify the function of BRs in plants as a complement to BR-deficient mutants. The brassinazole action site was also investigated by feeding BR biosynthesis intermediates to cress grown in the light.

Isolation and initial characterization of 13(2)-hydroxychlorophyll a induced by cyclohexanedione derivatives in tobacco cell suspension cultures

This paper reports that a new photobleaching compound, 2-(2-chloro-5-propoxycarbonylphenyl)aminomethylidene-5-5-dim ethyl- cyclohexane-1,3-dione (RWH-21), stimulates accumulation of 13(2)-hydroxychlorophyll a in cultured tobacco cells. This was shown based on isolation of 13(2)-hydroxychlorophyll a from pigment extracts of cultured tobacco cells by diode-array HPLC and subsequent fast atom bombardment mass spectrometry analysis. 13(2)-Hydroxychlorophyll a rapidly accumulates in tobacco cells both in the light and dark in the presence of RWH-21 (50 microM). Analysis of 13(2)-hydroxychlorophyll a formation in tobacco cells indicates that 13(2)-hydroxychlorophyll a is rapidly accumulated within 20 h incubation time both in the dark and light. Although the amount of 13(2)-hydroxychlorophyll a is continuously increased in the dark, the amount of 13(2)-hydroxychlorophyll a decreased remarkably in the light after 20 h incubation. Analysis of 13(2)-hydroxychlorophyll a formation and lipid peroxidation by determination malondialdehyde in tobacco cells suggests that RWH-21-induced 13(2)-hydroxychlorophyll a has the potential to cause a photodynamic action in cultured tobacco cells.

Opening of Rice Floret in Rapid Response to Methyl Jasmonate

Effects of methyl jasmonate (MeJA) on rice floret opening were investigated in seven cultivars or hybrid combinations covering various variety types. Intact or excised panicles, judged to have florets just before anthesis, were soaked in 4 x 10(-5) - 4 x 10(-3)M MeJA solutions for 2 min at different temperatures. The results indicated that MeJA significantly induced opening of rice florets within about 30 min, with the most rapid induction occurring just 6 min after treatment. Numbers of induced opening florets are correlated with MeJA concentrations. Higher concentrations of MeJA induced more florets. pH values had no influence on MeJA effect, but MeJA required less time and induced more florets at 34 degrees C than at 25 degrees C. As far as we know, this is the first evidence that floret opening is induced by plant hormones. CO(2) evolution from panicles was also increased by MeJA treatment. Field experiments revealed that perfect flowering synchrony between the cytoplasmic male sterile (CMS) and restorer lines in hybrid seed production could be obtained by spraying MeJA solution on CMS line plants at the rate of 25 mg/m(2). As a result, many more hybrid seeds were harvested.

Preparation and application of anti-idiotypic antibody against anti-gibberellin A4 antibody

A monoclonal anti-idiotypic antibody was raised against anti-gibberellin A4 (GA4) antibody, which recognizes biologically active gibberellins such as GA1 and GA4 specifically. Amino acid sequences of variable regions of both anti-GA4 and anti-idiotypic antibodies were analyzed. By using the property of the anti-idiotypic antibody to compete with GA1/4 in binding to the anti-GA4 antibody, we successfully applied the anti-idiotypic antibody to ELISA as a tracer for measuring GA1/4. The single-chain Fv (scFv) gene of the anti-idiotypic antibody was constructed, and scFv expressed in E. coli showed binding activity to anti-GA4 antibody. These results suggest the possible application of anti-idiotypic antibody as a handy and stable source of an enzymatic tracer for ELISA by production of fusion protein of the scFv and an appropriate enzyme.

Expression of a functional single-chain antibody against GA24/19 in transgenic tobacco

An anti-gibberellin A24/19 single-chain Fv gene was constructed from gamma and kappa genes cloned from a hybridoma cell line producing monoclonal antibody against gibberellin A24/19, biosynthetic precursors of gibberellin A4/1 which are biologically active per se. The single-chain Fv gene was introduced into tobacco plants after the binding activity of the single-chain Fv expressed in Escherichia coli was confirmed. When the single-chain Fv expression is targeted to endoplasmic reticulum, the plants could accumulate the single-chain Fv protein with the antigen binding activity up to 3.6% of the total soluble protein. On the other hand, when the expression is targeted to cytosol, accumulation of the single-chain Fv protein was not detected at all. The dwarf phenotype of the transgenic plants expressing the single-chain Fv protein, together with the preliminary analytical data indicating a decreased level of gibberellin A1 in the dwarf transgenics, suggested that the single-chain Fv decreased the concentration of bioactive gibberellins by trapping and inhibiting the metabolism of gibberellin A24 and/or A19 to gibberellin A4 and/or A1.

New lead compounds for brassinosteroid biosynthesis inhibitors

The first brassinosteroid biosynthesis inhibitor is reported. Among newly synthesized triazole derivatives, 4-(4-chlorophenyl)-2-phenyl-3-(1,2,4-triazoyl)butan-2-ol (6) was found to inhibit the growth of cress seedlings, and this inhibition was recovered by the treatment of brassinolide, suggesting that compound 6 primarily inhibits brassinosteroid biosynthesis.

Characterization of a protein kinase gene responsive to auxin and gibberellin in cucumber hypocotyls

By means of the PCR, cDNA clones encoding putative protein kinases have been obtained from cucumber hypocotyls. The abundance of the transcript of one of these genes, which was named CsPK3, increased on treatment with gibberellin (GA4) and/or auxin (IAA). We screened a cucumber cDNA library to clone CsPK3 cDNA. The cDNA clone (cCsPK3) encodes an open reading frame of 1,413 bp (471 amino acids), and its predicted amino acid sequence showed homology with those of serine/threonine protein kinases. Northern blot analysis indicated that IAA was more active than GA4 in increasing the level of CsPK3 mRNA in cucumber hypocotyls and that the increase in the level of CsPK3 mRNA on treatment with IAA was not inhibited by pretreatment with a protein synthesis inhibitor. The level of CsPK3 mRNA was high in hypocotyls of dark-grown cucumber seedlings and decreased to less than 50% of the original level within 15 min of the start of irradiation with white light.

Partial purification and characterization of a gibberellin-binding protein from seedlings of Azukia angularis

Little is known about mechanisms for the perception of gibberellin (GA), a phytohormone, by plants. A GA-binding protein (GBP) with receptor-like characteristics was partially purified from azuki bean (Azukia angularis) seedlings. Gibberellins that caused much elongation of azuki epicotyl sections showed strong binding affinity for the GBP, and their biosynthetic precursors and inactive metabolites had weak affinity for it. The apparent Kd value for GA4 was calculated to be 7 x 10(-10) M from Scatchard plots. The molecular weight of the GBP in the native state was estimated to be 25,000 by high-performance liquid chromatography with a gel-permeation column. The GBP may be one of the receptor candidates for GAs.

Biosynthesis of GA73 Methyl Ester in Lygodium Ferns

Biosynthesis of GA73 methyl ester (GA73-Me), the principal antheridiogen in Lygodium ferns, was investigated. From the methanol extract of prothallia of Lygodium circinnatum, GA25, GA73, GA73-Me, GA88-Me, and a few unknown GA73 derivatives were detected by GC-MS. Because the presence of GA25 suggests that GA24, a direct precursor of GA25, could also be present in L. circinnatum prothallia, we used feeding experiments to investigate the possibility that GA24 is a precursor of GA73-Me. In L. circinnatum prothallia, [2H2]GA24 was converted into [2H2]GA73-Me and a trace amount of [2H2]GA9-Me, whereas [2H3]GA9 was converted into [2H3]GA9-Me and [2H3]monohydroxy-GA9-Me. Because GA73-Me, GA9-Me, and their monohydroxy derivatives had been identified by GC-MS from the culture medium of L. circinnatum prothallia, our results suggest that GA73-Me is biosynthesized from GA24 via GA73, and that neither GA9 nor GA9-Me is a precursor of GA73-Me. Though the possibility had been suggested that GA73-Me is biosynthesized from 9,15-cyclo-GA9 (GA103), [2H2]GA103 was not converted into [2H2]GA73-Me.

Molecular cloning and characterization of a cDNA encoding the gibberellin biosynthetic enzyme ent-kaurene synthase B from pumpkin (Cucurbita maxima L.)

The first committed step in the formation of diterpenoids leading to gibberellin (GA) biosynthesis is the conversion of geranylgeranyl diphosphate (GGDP) to ent-kaurene. ent-Kaurene synthase A (KSA) catalyzes the conversion of GGDP to copalyl diphosphate (CDP), which is subsequently converted to ent-kaurene by ent-kaurene synthase B (KSB). A full-length KSB cDNA was isolated from developing cotyledons in immature seeds of pumpkin (Cucurbita maxima L.). Degenerate oligonucleotide primers were designed from the amino acid sequences obtained from the purified protein to amplify a cDNA fragment, which was used for library screening. The isolated full-length cDNA was expressed in Escherichia coli as a fusion protein, which demonstrated the KSB activity to cyclize [3H]CDP to [3H]ent-kaurene. The KSB transcript was most abundant in growing tissues, but was detected in every organ in pumpkin seedlings. The deduced amino acid sequence shares significant homology with other terpene cyclases, including the conserved DDXXD motif, a putative divalent metal ion-diphosphate complex binding site. A putative transit peptide sequence that may target the translated product into the plastids is present in the N-terminal region.

cDNA cloning and characterization of a gibberellin-responsive gene in hypocotyls of Cucumis sativus L

A cDNA clone corresponding to a gibberellin-responsive gene (CRG16) was isolated from cucumber hypocotyls. CRG16 was deduced to encode an extremely hydrophobic protein of 65 amino acids. The deduced sequence exhibited no significant homology to other proteins. Levels of CRG16 mRNA reflected the gibberellin-induced elongation of cucumber hypocotyls.

Identification of Antheridiogens in Lygodium circinnatum and Lygodium flexuosum

Antheridiogens in two species of Schizaeaceous ferns, Lygodium circinnatum and Lygodium flexuosum, were analyzed by gas chromatography-mass spectrometry. In L. circinnatum, gibberellin A73 (GA73) methyl ester (GA73-Me), which had originally been identified in L. japonicum, was identified as a principal antheridiogen, and the methyl esters of five known GAs (GA9, GA20, GA70, GA88, and 3-epi-GA88) were also identified as minor antheridiogens. In addition, four compounds corresponding to isomers of monohydroxy-GA73-Me were detected. One of these was shown to be 12[beta]-hydroxy-GA73-Me, the parent acid of which has been allocated the GA assignment GA96. The other three compounds, tentatively named X1, X2, and X3, have not been fully characterized. In L. flexuosum, GA73-Me was also identified as a major antheridiogen, with X2 being detected as a minor one. The total antheridium-formation activity in the culture medium of 7-week-old prothallia of L. circinnatum and L. flexuosum was more than 1000 times higher than that of L. japonicum. On the other hand, the response of gametophytes of the former two Lygodium ferns to GA73-Me was more than 100 times lower than that of L. japonicum.

Involvement of Jasmonic Acid in Elicitor-Induced Phytoalexin Production in Suspension-Cultured Rice Cells

It has been suggested that jasmonic acid (JA) could be an integral part of a general signal transduction system regulating inducible defense genes in plants. It was reported that treatment with an elicitor (N-acetylchitoheptaose) induced production of phytoalexin in suspension-cultured rice (Oryza sativa L.) cells. In this study, the role of JA in the induction of phytoalexin production by N-acetylchitoheptaose was investigated. Exogenously applied ([plus or minus])-JA (10-4 M) clearly induced the production of momilactone A, a major phytoalexin, in suspension-cultured rice cells. On the other hand, in rice cells treated with N-acetylchitoheptaose, endogenous JA was rapidly and transiently accumulated prior to accumulation of momilactone A. Treatment with ibuprofen, an inhibitor of JA biosynthesis, reduced production of momilactone A in the cells treated with N-acetylchitoheptaose, but the addition of ([plus or minus])-JA increased production of momilactone A to levels higher than those in the elicited rice cells. These results strongly suggest that JA functions as a signal transducer in the induction of biosynthesis of momilactone A by N-acetylchitoheptaose in suspension-cultured rice cells.

Purification and Properties of ent-Kaurene Synthase B from Immature Seeds of Pumpkin

ent-Kaurene synthase B (KSB) was purified 291-fold from a crude enzyme preparation from endosperm of pumpkin (Cucurbita maxima L.). Separation of ent-kaurene synthase A and KSB was achieved by hydrophobic interaction chromatography. The fractions containing KSB activity were further purified by diethylaminoethyl, phenyl, and hydroxyapatite column chromatography. Using sodium dodecyl phosphate-polyacrylamide gel electrophoresis, the purest enzyme preparation showed a major band at an apparent molecular mass of 81 kD. The amount of protein in this band was correlated with KSB activity after diethylaminoethyl and hydroxyapatite chromatography. The N terminus of the 81-kD protein was blocked. Therefore, the protein was partially digested with protease and the amino acid sequences of the resulting major peptide fragments were analyzed. A polyclonal antibody was raised against a synthetic peptide based on the longest peptide fragment combined with a keyhole limpet hemocyanin. The antibody recognized only the 81-kD denatured protein and not the native KSB. The properties of KSB were examined using the phenyl-purified enzyme preparation. The Km value for copalyl pyrophosphate was 0.35 [mu]M, and the optimal pH was 6.8 to 7.5. The KSB activity required divalent cations such as Mg2+, Mn2+, and Co2+, whereas Cu2+, Ca2+, and Ba2+ inhibited the activity.

cDNA cloning and characterization of gibberellin-responsive genes in photoblastic lettuce seeds

Two cDNA clones, cLRG5 and cLRG11, that respond to gibberellin (GA) were isolated from seeds of photoblastic lettuce (Lectuca sativa L. cv. Grand Rapids) by differential screening. Northern blot analysis indicated that the levels of LRG5 and LRG11 mRNAs were raised to slightly higher levels 10 h after the start of GA treatment and the levels were maintained at least for further 8 h, while those in the control seeds gradually decreased. Red light irradiation had effects similar to GA treatment. The cLRG5 insert encodes a putative polypeptide of 380 amino acids that is highly homologous to alcohol dehydrogenases from several higher plants. With regard to the cLRG11 insert, no homologous gene has been reported.

Synthesis and Structure Determination of Gibberellin-Derived Antheridiogens From Fern Gametophytes of the Lygodium Genus

Two successful and two unsuccessful synthetic routes are described for the conversion of commercially available fungal gibberellins to the antheridiogen GA73 methyl ester (5), originally isolated from gametophytes of the fern Lygodium japonicum. The more efficient route began with the Birch reduction of either the GA7 derivative (31) or methyl gibberellate 3,13-dimesylate (32) to give the ∆1(10),16-diene acid (33), which was converted into the ∆1,9-diene acid (40) by means of a four step procedure. This intermediate could be selectively hydrogenated to the ∆9-ene derivative which underwent iodolactonization and then elimination of HI to afford enone (29), Wittig methylenation of which furnished the target antheridiogen (5). In addition, (29) was functionalized at C12 by free radical bromination to give access to the 12β-hydroxy derivative of (5), i.e. (6), a new antheridiogen isolated from Lygodium circinnatum.

Structure of malformin B, a phytotoxic metabolite produced by Aspergillus niger

Malformin B, produced by Aspergillus niger, was separated into six compounds by HPLC. Their structures were determined by amino acid analyses, and by mass spectral and two-dimensional NMR experiments to be cyclic pentapeptides structurally related to malformin A1. Both the NMR and MS/MS experiments suggest cyclo-D-cysteinyl-D-cysteinyl-L-amino acid-D-amino acid-L-amino acid as the essential structure of malformins.

A mutant gene that increases gibberellin production in brassica

A single gene mutant (elongated internode [ein/ein]) with accelerated shoot elongation was identified from a rapid cycling line of Brassica rapa. Relative to normal plants, mutant plants had slightly accelerated floral development, greater stem dry weights, and particularly, increased internode and inflorescence elongation. The application of the triazole plant growth retardant, paclobutrazol, inhibited shoot elongation, returning ein to a more normal phenotype. Conversely, exogenous gibberellin A(3) (GA(3)) can convert normal genotypes to a phenotype resembling ein. The content of endogenous GA(1) and GA(3) were estimated by gas chromatography-selected ion monitoring using [(2)H]GA(1), as a quantitative internal standard and at day 14 were 1.5- and 12.1-fold higher per stem, respectively, in ein than in normal plants, although GA concentrations were more similar. The endogenous levels of GA(20) and GA(1), and the rate of GA(19) metabolism were simultaneously analyzed at day 7 by feeding [(2)H(2)]GA(19) and measuring metabolites [(2)H(2)]GA(20) and [(2)H(2)]GA(1) and endogenous GA(20) and GA(1), with [(2)H(5)]GA(20) and [(2)H(5)]GA(1) as quantitative internal standards. Levels of GA(1) and GA(20) were 4.6- and 12.9-fold higher, respectively, and conversions to GA(20) and GA(1) were 8.3 and 1.3 times faster in ein than normal plants. Confirming the enhanced rate of GA(1) biosynthesis in ein, the conversion of [(3)H]GA(20) to [(3)H]GA(1) was also faster in ein than in the normal genotype. Thus, the ein allele results in accelerated GA(1) biosynthesis and an elevated content of endogenous GAs, including the dihydroxylated GAs A(1) and A(3). The enhanced GA production probably underlies the accelerated shoot growth and development, and particularly, the increased shoot elongation.

Identification of gibberellins in the rice plant and quantitative changes of gibberellin A19 throughout its life cycle

The major endogenous gibberellin (GA) in shoots, roots and ears of the rice plant, Oryza sativa L. japonica cv. Nihonbare, was identified as GA19 by combined gas liquid chromatography-mass spectrometry (GC-MS) and GC-selected ion current monitoring (GC-SICM). Another GA present in these tissues in small quantity was tentatively identified as GA1 by GC-SICM, and GA4 may be present in the seeds (kernels) of 3rd-leaf-stage seedlings. Using GC-SICM, the GA19 content was quantified throughout the life cycle of rice plants. It was found to reach high levels (ca. 10-15 μg/kg fresh weight) in 3rd-leaf seedlings, at panicle initiation (shoots), and during heading and anthesis (ears). The levels of GA19 in Oryza sativa indica cv. T-136 underwent changes closely similar to those found in Nihonbare. The growth-promoting activity in rice of exogenous GA19 is generally considerably less than that of GA1. It therefore seems possible that GA19 functions as a "pool GA". The level of active GAs such as GA1 may be regulated by the rate of biosynthesis of GA19 or its metabolic conversions.

Isolation of gibberellins A26 and A 27 and their glucosides from immature seeds of Pharbitis nil

Two new gibberellins, gibberellins A26 and A27 (GA26 and GA27), and their glucosides have been isolated from immature seeds of Japanese morning-glory (Pharbitis nil), together with GA8 and its glucoside. GA26, GA27 and their glucosides showed only slight growth-promoting activities on seedlings of rice, dwarf maize and cucumber.

Isolation of two new gibberellins from immature seeds of Canavalia

Two new gibberellins, Canavalia gibberellin-I (CG-I) and Canavalia gebberellin-II (CG-II), were isolated from immature seeds of sword bean, Canavalia gladiata DC. The molecular formulas C19H22O7 and C19H22O6, were assigned to CG-I and CG-II, respectively, on the basis of high resolution mass, infrared and NMR spectra. The growth-promoting effects of CG-I and CG-II on dwarf maize mutants d 1 and d 5, rice seedlings and dwarf peas, Progress No. 5, are reported.

Isolation of water-soluble gibberellins from immature seeds of Pharbitis nil

The presence of three water-soluble gibberellins was confirmed in immature seeds of morning-glory (Pharbitis nil). The structure of the main component has been elucidated as 2-O-β-glucosyl-gibberellin A3. It shows marked growth-promoting activity on rice seedlings but is far less active on dwarf maize mutants d 1, d 2 and d 5.