The dominant non-gibberellin-responding dwarf mutant (D8) of maize accumulates native gibberellins

The endogenous gibberellins (GAs) were examined from young vegetative shoots of the dominant mutant, Dwarf-8, a GA-nonresponder, and normal maize; GA(44), GA(17), GA(19), GA(20), GA(29), GA(1), and GA(8), members of the early-13-hydroxylation pathway, were identified from both kinds of shoots by full-scan mass spectra and Kovats retention indices. In addition, we report the identification of 3-epi-GA(1), GA(3), GA(4), GA(5), GA(7), GA(9), GA(12), GA(15), GA(24), GA(34), and GA(53) by using the same criteria. [1,7,12,18-(14)C(4)]GA(53) and -GA(44), [17-(2)H(2)]GA(19), and [17-(13)C,(3)H(2)]GA(20), -GA(29), -GA(1), -GA(8), and -GA(5) were used as internal standards to determine the endogenous levels of these GAs by measurement of isotope dilution, using capillary gas chromatography and selected ion monitoring. Shoots of Dwarf-8 accumulate relatively high levels of GA(20), GA(1), and GA(8). The accumulation of GA(1) appears to be related to gene dosage. Since Dwarf-8 contains the same pattern of GAs as normals (including GA(1) and GA(3)), the genetic control point probably lies after GA(1) (and GA(3)). Thus Dwarf-8 may be a GA receptor mutant or a mutant that controls a product downstream from the binding of the bioactive GA to a receptor.