Controlled indole-3-acetaldoxime production through ethanol-induced expression of CYP79B2.

Indole-3-acetaldoxime (IAOx) is a key branching point between primary and secondary metabolism. IAOx serves as an intermediate in the biosynthesis of indole glucosinolates (I-GLSs), camalexin and the plant hormone indole-3-acetic acid (IAA). The cytochrome P450s CYP79B2 and CYP79B3 catalyze the conversion of tryptophan to IAOx. CYP83B1 channels IAOx into I-GLS biosynthesis, CYP71A13 channels IAOx into camalexin biosynthesis, whereas the IAOx-metabolizing enzyme in IAA biosynthesis is not known. In this report, we demonstrate controlled production of I-GLSs by introducing an ethanol (EtOH)-inducible CYP79B2 construct into double (cyp79b2 cyp79b3) or triple (cyp79b2 cyp79b3 cyp83b1) mutant lines. We show EtOH-dependent induction of camalexin and identify a number of candidate IAA homeostasis- or defense-related genes by clustered microarray analysis. The transgenic mutant lines are thus promising tools for elucidating the interplay between primary and secondary metabolism.