Abstract
Indole-3-acetic acid (IAA), a naturally occurring auxin, is a pivotal plant hormone that controls many aspects of plant growth and development. Recently, several IAA biosynthetic genes, YUCCA, CYP79B2/CYP79B3 and TAA1, were identified in Arabidopsis. Genetic studies on the IAA biosynthesis have suggested that two different pathways involving CYP79B or YUCCA genes may be converged at possible intermediates such an indole-3-acetaldoxyme (IAOx). To address this question, we analyzed possible IAA intermediates in plants using LC-ESI-MS/MS. We found that the majority of IAOx, indole-3-acetonitrile and indole-3-acetamide were produced from the CYP79B pathway in Arabidopsis. IAOx was not detected from rice, maize and tobacco, which presumably do not have CYP79B family. These results indicate that IAA biosynthetic pathway via IAOx is not a conventional but a species-specific pathway in plants. LC-ESI-MS/MS analysis of other proposed IAA intermediates will be also discussed.
