The biosynthesis of ent-kaurene in germinating seeds and the function of 2-oxoglutarate in gibberellin biosynthesis

Abstract

The two topics of this paper deal with different parts of the gibberellin (GA) biosynthetic pathway. The diterpene hydrocarbon ent-kaurene is the first tetracyclic precursor of gibberellins. Its two-step formation from geranylgeranyl pyrophosphate through the action of kaurene synthetase A and B initiates the diversion of the GA pathway from the general terpenoid pathway, and is a likely point for GA biosynthesis regulation. The capacity of a tissue to biosynthesize ent-kaurene is usually measured by the conversion of labelled precursors, such as mevalonate or geranylgeranyl pyrophosphate, to ent-kaurene in cell-free systems. This method works well with immature seeds, which are often highly active for GA biosynthesis, but cell-free systems from germinating seeds and seedlings, which are less active, give erratic and often negative results. We report here a new method of measuring ent-kaurene formation in vivo. In this procedure, ent-kaurene oxidation is inhibited by the addition of a plant growth retardant, thus causing ent-kaurene to accumulate, presumably at the same rate as its normal biosynthesis. The accumulation is sufficient, even in seedlings, to be quantified by the use of isotope dilution and GC-SIM (Großelindemann et al., 1991).KeywordsSuccinic AcidImmature SeedMevalonic AcidSuccinate ProductionCucurbita MaximumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.