Bernard O. Phinney

Studies on the biosynthesis of gibberellins from (−)-kaurenoic acid in cultures of Gibberella Fujikuroi

Abstract Gibberella fujikuroi utilizes (−)-kaur-16-en-19-oic acid as a precursor for the synthesis of gibberellins. A study of the time-course of the conversion of kaurenoic acid into gibberellins provides evidence that the sequence of steps involves an overall change toward higher oxidation levels, with GA-4 and GA-7 at an earlier stage on the synthetic pathway than GA-1 and GA-3.

Internode length in Zea mays L.

Abstract[13C, 3H]Gibberellin A20 (GA20) has been fed to seedlings of normal (tall) and dwarf-5 and dwarf-1 mutants of maize (Zea mays L.). The metabolites from these feeds were identified by combined gas chromatography-mass spectrometry. [13C, 3H]Gibberellin A20 was metabolized to [13C, 3H]GA29-catabolite and [13C, 3H]GA1 by the normal, and to [13C, 3H]GA29 and [13C, 3H]GA1 by the dwarf-5 mutant. In the dwarf-1 mutant, [13C, 3H]GA20 was metabolized to [13C, 3H]GA29 and [13C, 3H]GA29-catabolite; no evidence was found for the metabolism of [13C, 3H]GA20 to [13C, 3H]GA1. [13C, 3H]Gibberellin A8 was not found in any of the feeds. In all feeds no dilution of 13C in recovered [13C, 3H]GA20 was observed. Also in the dwarf-5 mutant, the [13C]label in the metabolites was apparently undiluted by endogenous [13C]GAs. However, dilution of the [13C]label in metabolites from [13C, 3H]GA20 was observed in normal and dwarf-1 seedlings. The results from the feeding studies provide evidence that the dwarf-1 mutation of maize blocks the conversion of GA20 to GA1.

Comparison of ent-kaurene and ent-isokaurene synthesis in cell-free systems from etiolated shoots of normal and dwarf-5 maize seedlings

An active cell-free system, prepared from young etiolated shoots of normal Zea mays seedlings, was shown to biosynthesize the terpenoid hydrocarbons ent-kaur-16-ene, squalene and phytoene from mevalonic acid. The biosynthesis of ent-kaur-16-ene from mevalonic acid was compared using cell-free systems obtained from normal and dwarf-5 seedlings. ent-Kaur-16-ene was the predominant diterpene hydrocarbon synthesized by extracts from the normals; however, ent-kaur-15-ene was the major diterpene hydrocarbon synthesized by the dwarf-5 mutants. ent-Kaur-15-ene and ent-kaur-16-ene were also produced as minor products in the normal and dwarf-5 systems, respectively. The possible significance of the synthesis of the ‘wrong isomer’ (ent-kaur-15-ene) by the mutant is discussed.

Growth Response of the d-5 and an-1 Mutants of Maize to Some Kaurene Derivatives.

(—)-Kaur-16-en-19-oic acid and (—)-kaur-16-en-19-oloxygenated derivatives of (—)-kaurene, stimulated seedlingelongation for the two nonallelic dwarf mutants of maize, d-5 and an-1. Replacement of the exocyclic methylene groupattached to ring D by a keto-, methyl-, hydroxymethyl-, carboxy-, or methylcarboxy group resulted in compounds which were biologically inactive. These kaurene derivatives are structurally related to the gibberellins which produce a similar type of elongation for the d-5 and an-1 mutants.

Position of the metabolic block for gibberellin biosynthesis in mutant b1-41a of Gibberella fujikuroi☆

Abstract Mutant B1-41a, obtained by UV-irradiation of Gibberella fujikuroi strain GF-1a, does not metabolise mevalonic acid lactone (MVL), ent -kaur-16-ene, ent -kaurenol, and ent -kaurenal to gibberellins. ent -Kaur-16-ene-19-oic acid is completely metabolised to give the same gibberellins in similar concentration as unsupplemented cultures of the parent strain. It is concluded that this mutant is blocked for gibberellin synthesis at the step from ent -kaurenal to ent -kaurenoic acid. Comparison of the incorporation of MVL into GA 3 by the mutant and the parent strains indicate that the metabolic block is 97·5% effective. A method of preparing ent -kaur-16-ene, labelled at C-15 and C-17 by [ 2 H] and [ 3 H] is described.

Hormones of young tassels of Zea mays

Abstract The ethyl acetate-soluble acids from an aqueous methanolic extract of young tassels from Zea mays plants were fractionated by treatment with PVP, then by chromatography on a column of celite-charcoal. Methylated and trimethylsilylated fractions were analysed by GC/MS and the following compounds were identified by comparison with reference spectra: GA17, GA19, GA20, GA44, GA53, ABA, phaseic acid and dihydrophaseic acid. Evidence is also presented for the presence of metabolise C of ABA and of a 16,17-dihydro-17-hydroxy-derivative of GA53. In addition, the presence of small amounts of GA1, GA8 and GA29, was indicated from a derivatized fraction analysed by capillary GC/SICM.

The metabolism of steviol to 13-hydroxylated ent-Gibberellanes and ent-kauranes ☆

Abstract Steviol( ent -13-hydroxykaur-16-en-19-oic acid) is rapidly metabolised by the mutant B1-41a of Gibberellafujikuroi . The initial product is the ent - 7-α-hydroxy derivative which is then further metabolised to gibberellins A 1 , A 18 , A 19 , A 20 , 13-hydroxy GA 12 , the ent -6α, 7α, 13- and ent -6β, 7α, 13 (19,6-lactone)-trihydroxykaurenoic acids, and a seco-ring B diacid. This apparently low substrate specificity of the enzymes operative beyond the block in the mutant B1-41a provides a useful model for the biosynthetic pathways to 13-hydroxylated gibberellins of higher plants and a preparative route to these plant gibberellins.

The biosynthesis of kaurenolide diterpenoids by gibberella fujikuroi

Abstract The biosynthesis of 7β-hydroxy- and 7β,18-dihydroxy-kaurenolides from ent -kaur-16-en-19-oic acid has been investigated by incubating unlabelled

The metabolism of gibberellin A20 to gibberellin A1 by tall and dwarf mutants of Oryza sativa and Arabidopsis thaliana

The purpose of this study was to demonstrate the metabolism of gibberellin A20 (GA20) to gibberellin A1 (GA1) by tall and mutant shoots of rice (Oryza sativa L.) and Arabidopsis thaliana (L.) Heynh. The data show that the tall and dx mutant of rice and the tall and ga5 mutant of Arabidopsis metabolize GA20 to GA1. The data also show that the dy mutant of rice and the ga4 mutant of Arabidopsis block the metabolism of GA20 to GA1. [17–13C,3H]GA20 was fed to tall and the dwarf mutants, dx and dy, of rice and tall and the dwarf mutants, ga5 and ga4, of Arabidopsis. The metabolites were analyzed by high-performance liquid chromatography and full-scan gas chromatography-mass spectrometry together with Kovats retention index data. For rice, the metabolite [13C]GA, was identified from tall and dx seedlings; [13C]GA1 was not identified from the dy seedlings. [13C]GA29 was identified from tall, dx, and dy seedlings. For Arabidopsis, the metabolite [13C]GA1 was identified from tall, ga5, and ga4 plants. The amount of [13C]GA1 from ga4 plants was less than 15% of that obtained from tall and ga5 plants. [13C]GA29 was identified from tall, ga5, and ga4 plants. [13C]GA5 and [13C]GA3 were not identified from any of the six types of plant material.

Diterpene acids from Helianthus species and their microbiological conversion by Gibberella fujikuroi, mutant B1-41a

Abstract The diterpene acid content in 10 species of Helianthus has been investigated. Ent-12,16-cyclokauranoic acid, isolated from H. annuus, is converted into a series of 12,16-cyclogibberellins by cultures of Gibberella fujikuroi, mutant B1-41a, and 12,16-cyclogibberellins A9, and A12 have been isolated. Ent-12β-acetoxykaurenoic acid and ent-13(S)-angeloxyatisenoic acid have been isolated from H. decapetalus; the metabolism of ent-13(S)-hydroxyatisenoic acid and atisenoic acid by B1-41a is also described.