A. Ostin et al., An in vitro system from maize seedlings for tryptophan-independent indole-3-acetic acid biosynthesis, PLANT PHYSL, 119(1), 1999, pp. 173-178
The enzymatic synthesis of indole-3-acetic acid (IAA) from indole by an in
vitro preparation from maize (Zea mays L.) that does not use tryptophan (Tr
p) as an intermediate is described. Light-grown seedlings of normal maize a
nd the maize mutant orange pericarp were shown to contain the necessary enz
ymes to convert [C-14]indole to IAA. The reaction was not inhibited by unla
beled Trp and neither [C-14]Trp nor [C-14]serine substituted for [C-14]indo
le in this in vitro system. The reaction had a pH optimum greater than 8.0,
required a reducing environment, and had an oxidation potential near that
of ascorbate. The results obtained with this in vitro enzyme preparation pr
ovide strong, additional evidence for the presence of a Trp-independent IAA
biosynthesis pathway in plants.