Qualitative and Quantitative Analyses of Gibberellins in Vegetative Shoots of Normal, dwarf-1, dwarf-2, dwarf-3, and dwarf-5 Seedlings of Zea mays L.

Abstract

Gibberellins A12 (GAI2), GA53, GA44, GA19, GA,7, GA20, GA29, GA1, and GAB have been identified from extracts of vegetative shoots of normal (wild type) maize using full scan capillary gas chromatography-mass spectrometry and Kovats retention indices. Seven of these gibberellins (GAs) have been quantified by capillary gas chromatography-selected ion monitoring using internal standards of 114C41GA53, I'4C41GA44, 12H21 GA1I, 113C,IGA2o, 1'3C,IGA29, 113C,IGAI, and 1'3C,JGA8. Quantitative data from extracts of normal, dwarf-1, dwarf-2, dwarf-3, and dwarf-5 seedlings support the operation of the early 13-hydroxylation pathway in vegetative shoots of Zea mays. These data support the positions in the pathway blocked by the mutants, previously assigned by bioassay data and metabolic studies. The GA levels in dwarf-2, dwarf-3, and dwarf-5 were equal to, or less than, 2.0 nanograms per 100 grams fresh weight, showing that these mutants are blocked for steps early in the pathway. In dwarf-1, the level of GA, was very low (0.23 nanograms per 100 grams fresh weight) and less than 2% of that in normal shoots, while GA20 and GA29 accumulated to levels over 10 times those in normals; these results confirm that the dwarf-1 mutant blocks the conversion of GA20 to GA,.Since the level of GAs beyond the blocked step for each mutant is greater than zero, each mutated gene probably codes for an altered gene product, thus leading to impaired enzyme activities. (8,19), and GA20 to GA, (19); third, bioassay data, using the dwarf-l (dl), dwarf-2 (d2), dwarf-3 (d3) and dwarf-5 (d5) mutants indicate that these single-gene, nonallelic mutants block specific steps in the early 13-hydroxylation pathway. The pattern of response suggests the position in the pathway blocked by each mutant. For example, GA20 and GA, are both highly active when assayed on d5 whereas GA20 is 1% as active as GA, when assayed on dl. Thus, the d5 mutant blocks a step before GA20, and the dl mutant the late step, GA20 to GA,. In addition, the GA precursor ent-kaurene is active on d5, suggesting that the d5 block is before ent-kaurene (Fig. 1) (6).In this paper, evidence is presented for the presence of GA12, GA53, GA44, GA,9, GA17, GA20, GA29, GA,, and GA8 in the seedling shoots of normal maize (Fig. 1). The data are based on full scan mass spectra and Kovats retention indices (14) from capillary GC-MS. In addition, quantitative data are presented for the levels of specific endogenous GAs in normal, dl, d2, d3, and d5 seedlings using labeled internal standards and GC-SIM.3 These data provide additional support for the positions of the steps in the metabolic pathway blocked by the mutant genes (Fig. 1).The early 13-hydroxylation pathway (Fig. 1) for GA biosynthesis was first established for seeds of Pisum sativum (1 1, 17). This pathway has also been proposed for shoots of Zea mays (7,16). Four lines of evidence support the presence of this pathway and its operation in the control of shoot elongation in maize.First, eight members of the pathway, GA53, GA44, GA,9...

The Metabolism of Gibberellin A20 to Gibberellin A1 by Tall and Dwarf Mutants of Oryza sativa and Arabidopsis thaliana

“…Each purified, radioactive fraction selected for GC-MS was methylated and trimethylsilylated as described by Fujioka et al (1988) prior to analysis by GC-MS. The instrument and conditions for full-scan GC-MS were as described by Gaskin et al (1984).…”

Gibberellins and Stem Growth as Related to Photoperiod in Silene armeria L.

“…Positive ion electron impact mass spectra at 70 eV were acquired scanning from 50 to 800 amu at 1 s per scan cycle. For calculating the endogenous GA content, the contribution from natural isotopes from the unlabeled derivatized GAs was measured and the concentration of GA,, GA20, GAI9, and GA53 estimated from the peak area ratios 506/508, 418/420, 434/436, and 448/450, respectively, by the formula in Fujioka et al (2).…”

Gibberellin Biosynthesis Mutations and Root Development in Pea

“…For example, root development is altered in the maize d5 mutant (Baluska et al, 1993), and excised roots of the gib-1 (tomato) and d1 (maize) mutants grew more slowly than the corresponding wild-type lines (Mertz, 1966;Butcher et al, 1990;Barlow et al, 1991). Shoots of these mutants are known to be GA 1 deficient (Fujioka et al, 1988;Hedden and Lenton, 1988), and it has been assumed that this deficiency extends to the roots. GA biosynthesis inhibitors are also known to inhibit root elongation in wild-type lines of tomato (Butcher et al, 1990), lettuce (Tanimoto, 1990), and maize (Baluska et al, 1993), and this inhibition is overcome by application of bioactive GA, providing further evidence that GAs are important for root growth.…”