Biosynthetic Origin of Gibberellins A(3) and A(7) in Cell-Free Preparations from Seeds of Marah macrocarpus and Malus domestica.

Cell-free preparations from seeds of Marah macrocarpus L. and Malus domestica L. catalyzed the conversion of gibberellin A(9) (GA(9)) and 2,3-dehydroGA(9) to GA(7); GA(9) was also metabolized to GA(4) in a branch pathway. The preparation from Marah seeds also metabolized GA(5) to GA(3) in high yield; GA(6) was a minor product and was not metabolized to GA(3). Using substrates stereospecifically labeled with deuterium, it was shown that the metabolism of GA(5) to GA(3) and of 2,3-dehydroGA(9) to GA(7) occurs with the loss of the 1beta-hydrogen. In cultures of Gibberella fujikuroi, mutant B1-41a, [1beta,2beta-(2)H(2)]GA(4), was metabolized to [1,2-(2)H(2)]GA(3) with the loss of the 1alpha- and 2alpha-hydrogens. These results provide further evidence that the biosynthetic origin of GA(3) and GA(7) in higher plants is different from that in the fungus Gibberella fujikuroi.

Identification and localization of gibberellins in maturing seeds of the cucurbit Sechium edule, and a comparison between this cucurbit and the legume Phaseolus coccineus.

Twenty known gibberellins (GAs) have been identified by combined capillary gas chromatography-mass spectrometry in extracts from less than 10 g fresh weight of maturing seeds of the cucurbit Sechium edule Sw. The GAs are predominantly 3- and-or 13-hydroxylated. This is the first reported identification of non-conjugated 13-hydroxylated GAs in a cucurbit. Gibberellin A8 and gibberellin A8-catabolite are the major GAs in terms of quantity and are largely accumulated in the testa. The catabolites of 2ß-hydroxylated GAs are α,ß-unsaturated ketones which no longer possess of a γ-lactone. They were hitherto known only in legumes. The presence of GA8-catabolite as a major component of Sechium seeds indicates that the distribution of these GA-catabolites may be more widespread than previously envisaged. The localization of known GAs in maturing seeds of the legume Phaseolus coccineus L. was found to resemble closely that in Sechium. Gibberellin A8, a putative conjugate of GA8 and GA8-catabolite are accumulated in the testa. The localization in the testa of end-products of the GA-biosynthetic pathway, which was first observed in maturing seeds of Pisum sativum, and is now described in Phaseolus and Sechium, may be a general feature of seed development.