Abstract
A time-course study is described relating the enzyme activities for GA20 metabolism with seed development in Phaseolus vulgaris L. Enzyme activity for the 3β-hydroxylation of GA20 to GA1, and for the 2,3-desaturation of GA20 to GA5, was confined to the cotyledons and showed maximal specific activity at 21 d after anthesis. These enzyme activities co-occurred, together with a much lower level of activity for the 2β-hydroxylation of GA20 to GA29. The observed rates of GA1, GA5 and GA29 formation from GA20 were constant under a range of incubation conditions. Enzyme activity for the conversion of GA1 to GA8 was detected only in embryos of seed from 40 d after anthesis. By deuterium-labelling and analysis of the products by gas chromatography-selected ion monitoring it was shown that 2β-hydroxylation of GA1 to GA8 and 3β-hydroxylation of GA20 to GA1 occur with retention of configuration and that the conversion of GA20 to GA5 occurs with loss of the 2β- and 3β-hydrogens. These results establish that GA1 is not formed from GA20 via GA5.
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Abbreviations
- GAn :
-
Gibberellin An
- GC:
-
gas chromatography
- HPLC:
-
high-performance liquid chromatography
- MS:
-
mass spectrometry
- SIM:
-
selected-ion monitoring
- THO:
-
tritiated water
References
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Albone, K., Gaskin, P., MacMillan, J. et al. Enzymes from seeds of Phaseolus vulgaris L.: Hydroxylation of gibberellins A20 and A1 and 2,3-dehydrogenation of gibberellin A20 . Planta 177, 108–115 (1989). https://doi.org/10.1007/BF00392160
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DOI: https://doi.org/10.1007/BF00392160