Gibberellin A(3) Is Biosynthesized from Gibberellin A(20) via Gibberellin A(5) in Shoots of Zea mays L |
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Authors: | Fujioka S Yamane H Spray C R Phinney B O Gaskin P Macmillan J Takahashi N |
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Institution: | Department of Biology, University of California, Los Angeles, Los Angeles, California 90024. |
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Abstract: | 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). |
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