Abstract
Multiple pathways have been proposed for the biosynthesis of auxin, indole-3-acetic acid (IAA), in plants, and the underlying intermediates are still largely unknown. Indole-3-acetaldoxime (IAOX) has been assumed as a possible intermediate of the Yucca pathway. IAOX has been defied as an intermediate of indole glucosinolate (IG) biosynthesis in Arabidopsis. To distinguish whether IAOX is involved in the Yucca pathway, we developed a new method to analyze IAOX using LC-TOF-MS/MS and D5-IAOX. As a result, IAOX was detected from wild type seedlings of Arabidopsis, whereas it was not found in the double knockout mutants of Cyp79B2 and Cyp79B3 genes, which encode cytochrome P450 monooxygenases catalyzing the conversion of TRP to IAOX. In addition, we were not able to detect any IAOX from non-crucifer plants that we analyzed. From these results, we concluded that IAOX is involved in the IG biosynthetic pathway in crucifer plants, but not in the Yucca pathway.
