GC-MS identification of GA20-13-O-glucoside formed from GA20 in normal plants and dwarf-1 mutants ofZea mays L.

After feeding GA₂₀ to excised seedlings ofZea mays L. normals (N) and dwarf-1 mutants (d1), GA₂₀-13-O-glucoside (9) was identified by HPLC and by GC-MS of its permethylated derivative. The glucosylation rate of GA₂₀ was found to be higher in the dwarf-1 mutant (26%) than in the normal plant (3.6%). This article includes a GC-MS study in which diagnostic fragments from the spectra of permethylated synthetic GA glucosides have been selected that proved to be useful for the identification of permethylated GA glucosides.     

Gibberellin A(3) Is Biosynthesized from Gibberellin A(20) via Gibberellin A(5) in Shoots of Zea mays L

[17-¹³C,³H]-Labeled gibberellin A₂₀ (GA₂₀), GA₅, and GA₁ were fed to homozygous normal (+/+), heterozygous dominant dwarf (D8/+), and homozygous dominant dwarf (D8/D8) seedlings of Zea mays L. (maize). ¹³C-Labeled GA₂₉, GA₈, GA₅, GA₁, and 3-epi-GA₁, as well as unmetabolized [¹³C]GA₂₀, were identified by gas chromatography-selected ion monitoring (GC-SIM) from feeds of [17-¹³C, ³H]GA₂₀ to all three genotypes. ¹³C-Labeled GA₈ and 3-epi-G₁, as well as unmetabolized [¹³C]GA₁, were identified by GC-SIM from feeds of [17-¹³C, ³H]GA₁ to all three genotypes. From feeds of [17-¹³C, ³H]GA₅, ¹³C-labeled GA₃ and the GA₃-isolactone, as well as unmetabolized [¹³C]GA₅, were identified by GC-SIM from +/+ and D8/D8, and by full scan GC-MS from D8/+. No evidence was found for the metabolism of [17-¹³C, ³H]GA₅ to [¹³C]GA₁, either by full scan GC-mass spectrometry or by GC-SIM. The results demonstrate the presence in maize seedlings of three separate branches from GA₂₀, as follows: (a) GA₂₀ → GA₁ → GA₈; (b) GA₂₀ → GA₅ → GA₃; and (c) GA₂₀ → GA₂₉. The in vivo biogenesis of GA₃ from GA₅, as well as the origin of GA₅ from GA₂₀, are conclusively established for the first time in a higher plant (maize shoots).     

Biosynthetic Origin of Gibberellins A(3) and A(7) in Cell-Free Preparations from Seeds of Marah macrocarpus and Malus domestica

Cell-free preparations from seeds of Marah macrocarpus L. and Malus domestica L. catalyzed the conversion of gibberellin A₉ (GA₉) and 2,3-dehydroGA₉ to GA₇; GA₉ was also metabolized to GA₄ in a branch pathway. The preparation from Marah seeds also metabolized GA₅ to GA₃ in high yield; GA₆ was a minor product and was not metabolized to GA₃. Using substrates stereospecifically labeled with deuterium, it was shown that the metabolism of GA₅ to GA₃ and of 2,3-dehydroGA₉ to GA₇ occurs with the loss of the 1β-hydrogen. In cultures of Gibberella fujikuroi, mutant B1-41a, [1β,2β-²H₂]GA₄, was metabolized to [1,2-²H₂]GA₃ with the loss of the 1α- and 2α-hydrogens. These results provide further evidence that the biosynthetic origin of GA₃ and GA₇ in higher plants is different from that in the fungus Gibberella fujikuroi.     

Genetic variation of recent Alu insertions in human populations

The Alu family of intersperesed repeats is comprised of ovr 500,000 members which may be divided into discrete subfamilies based upon mutations held in common between members. Distinct subfamilies of Alu sequences have amplified within the human genome in recent evolutionary history. Several individual Alu family members have amplified so recently in human evolution that they are variable as to presence and absence at specific loci within different human populations. Here, we report on the distribution of six polymorphic Alu insetions in a survey of 563 individuals from 14 human population groups across several continents. Our results indicate that these polymorphic Alu insertions probably have an African origin and that there is a much smaller amount of genetic variation between European populations than that found between other populations groups. Present address: Department of Pathology, Stanley S. Scott Cancer Center, Louisiana State University Medical Center, 1901 Perdido St., New Orleans, LA 70112 Correspondence to: M.A. Batzer     

Time-Dependent Effects of Progressive Gamma -Linolenate Feeding on Hyperphagia,Weight Gain,and Erythrocyte Fatty Acid Composition During Growth of Zucker Obese Rats

Obese Zucker rats (fa/fa) have low levels of arachidonic acid (AA) in liver phospholipids (PL). We have previously shown that a 70% gamma-linolenate concentrate (GLA; an AA intermediate) fed at a fixed dose (0.07 g/day) normalized hepatic PL AA and reduced weight gain selectively in the obese animals. In a follow-up study, 16 obese (fa/fa) and 16 lean (Fa/Fa) 4-week-old male rats were randomized into 4 groups of 8 each and gavaged daily with soybean oil (SOY) containing 55% 18:2ω6 (an AA precursor) or GLA, using a progressive dose (≤ 5% of total calories) based on body weight. A defined diet with 11% of energy as SOY was fed ad libitum for 60 days. GLA obese had lower body weight (p<0.0001) and 60-day cumulative food intake (p<0.05) compared to SOY obese, but neither parameter differed between the lean groups. For the last twenty days cumulative food intake was identical for GLA obese and SOY lean, whereas SOY obese consumed 18% more (p<0.05). Thus the progressive dose of GLA selectively suppressed hyperphagia in obese Zucker rats. Erythrocytes collected at 15-day intervals showed parallel increases in AA in both genotypes over time, suggesting normal AA availability during rapid growth. Thus, the reduced PL AA in the livers from the obese rats probably reflects impaired distribution in selected tissues rather than reduced hepatic production. Due to the potential health risks of enriching tissue lipids with AA, great caution is advised in considering GLA as therapy for human obesity.     

IDENTIFICATION OF CYTOKININS IN SARGASSUM MUTICUM (PHAEOPHYTA) AND PORPHYRA PERFORATA (RHODOPHYTA)1

Combined gas chromatography-mass spectrometry (GCMS) was used to identify and quantify specific cytokinins from Porphyra perforate J. Ag. and Sargassum muticum (Yendo) Fensh. The level of isopentenyladenosine was estimated to be 0.6 μ·kg^?1 fresh weight in Porphyra and 0.9 μ·kg^?1 fresh weight in Sargassum. The level of cis-zeatin riboside was estimated to be 0.2 μ·kg^?1 fresh weight in Sargassum. This is the first definitive identification of a cytokinin from a red alga, and the second report from a brown alga.     

Gibberellin A13 7-aldehyde: A proposed intermediate in the fungal biosynthesis of gibberellin A3

Gibberellin A₁₃ 7-aldehyde, previously proposed as an intermediate in the fungal biosynthesis of gibberellin A₃, has been prepared from gibbere     

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

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 A₁, A₁₈, A₁₉, A₂₀, 13-hydroxy GA₁₂, 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.