Metabolism of gibberellins in a cell-free system from immature seeds of Phaseolus vulgaris L. |
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Authors: | M. Takahashi Y. Kamiya N. Takahashi J. E. Graebe |
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Affiliation: | (1) Institute of Physical and Chemical Research, 351-01 Wako-shi, Saitama, Japan;(2) Pflanzenphysiologisches Institut der Universität, Untere Karspüle 2, D-3400 Göttingen, Federal Republic of Germany |
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Abstract: | The biosynthetic steps from gibberellin A12-aldehyde (GA12-aldehyde) to C19-GAs were studied by means of a cell-free system from the embryos of immature Phaseolus vulgaris seeds. Stable-isotope-labeled GAs were used as substrates and the products were identified by gas chromatography-mass spectrometry. Gibberellin A12-aldehyde was converted to GA4 via non-hydroxylated intermediates and to GA1 via 13-hydroxylated intermediates. 13-Hydroxylation took place at the beginning of the pathway by the conversion of GA12-aldehyde to GA53-aldehyde. The conversion of GA20 to GA5 and GA6 was also shown but no 2-hydroxylating activity was found. Endogenous GAs from embryos and testas of 17-dold seeds were re-examined by gas chromatography-selected ion monitoring using stable-isotopelabeled GAs as internal standards. Gibberellins A9, A12, A15, A19, A23, A24, and A53 were identified for the first time in P. vulgaris, in addition to GA1, GA4, GA5, GA6, GA8, GA17, GA20, GA29, GA37, GA38 and GA44, which were previously known to occur in this species. The levels of all GAs, except the 2-hydroxylated ones, were greater in the embryos than in the testas. Conversely, the contents of GA8 and GA29, both 2-hydroxylated, were much higher in the testas than in the embryos.Abbreviations GAn gibberellin An - GC-MS gas chromatography-mass spectrometry - GC-SIM gas chromatography-selected ion monitoring - HPLC high-performance liquid chromatography - TLC thin-layer chromatography - m/z ion of mass |
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Keywords: | Gibberellin biosynthesis Phaseolus (gibberellins) Seed (gibberellins) |
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