G. Davis et al., Gibberellin biosynthesis in maize. Metabolic studies with GA(15), GA(24), GA(25), GA(7), and 2,3-dehydro-GA(9), PLANT PHYSL, 121(3), 1999, pp. 1037-1045
[17-C-14]-Labeled GA(15), GA(24), GA(25), GA(7), and 2,3-dehydro-GA(9) were
separately injected into normal, dwarf-1 (d1), and dwarf-5 (d5) seedlings
of maize (Zea mays L.). Purified radioactive metabolites from the plant tis
sues were identified by full-scan gas chromatography-mass spectrometry and
Kovats retention index data. The metabolites from GA(15) were GA(44), GA(19
), GA(20), GA(113), and GA(15)-15,16-ene (artifact?). GA(24) was metabolize
d to GA(19), GA(20), and GA(17). The metabolites from GA(25) were GA(17), G
A(25) 16 alpha,17-H-2-17-OH, and HO-GA(25) (hydroxyl position not determine
d). GA(7) was metabolized to GA(30), GA(3), isoGA(3) (artifact?), and trace
amounts of GA(7)-diene-diacid (artifact?). 2,3-Dehydro-GA(9) was metaboliz
ed to GA(5), GA(7) (trace amounts), 2,3-dehydro-GA(10) (artifact?), GA(31),
and GA(62). Our results provide additional in vivo evidence of a metabolic
grid in maize (i.e. pathway convergence). The grid connects members of a p
utative, non-early 3,13-hydroxylation branch pathway to the corresponding m
embers of the previously documented early 13-hydroxylation branch pathway.
The inability to detect the sequence GA(12) --> GA(15) --> GA(24) --> GA(9)
indicates that the non-early 3,13-hydroxylation pathway probably plays a m
inor role in the origin of bioactive gibberellins in maize.