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; GA44, GA17, GA19, GA20, GA29, GA1, and GA8, 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-GA1, GA3, GA4, GA5, GA7, GA9, GA12, GA15, GA24, GA34, and GA53 by using the same criteria. [1,7,12,18-14C4]GA$_{53}$ and -GA44, [17-2H2]GA19, and [17-13C,3H2]GA< latex>$_{20}$, -GA29, -GA1, -GA8, and -GA5 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 GA20, GA1, and GA8. The accumulation of GA1 appears to be related to gene dosage. Since Dwarf-8 contains the same pattern of GAs as normals (including GA1 and GA3), the genetic control point probably lies after GA1 (and GA3). 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.