LC-ESI-MS/MS Analysis of Indole-3-acetaldehyde in Plants

Abstract

Auxins are a group of phytohormones that act in many aspects of plant growth and development. Indole-3-acetic acid (IAA) is a naturally occurring auxin, whose biosynthetic pathway is not fully understood. To elucidate the IAA biosynthetic pathway, we have been developing methods for the analysis of labile IAA intermediates by LC-ESI-MS/MS. Indole-3-acetaldehyde (IAAld) has been proposed as a common IAA biosynthetic intermediate, but not much is known about how IAAld is produced in plants. Here we present a direct analysis method for IAAld in plants using LC-ESI-MS/MS. Using our IAAld analysis method, we detected IAAld in Arabidopsis without any derivatization. When stable isotope-labeled indole or tryptophan was fed to Arabidopsis, IAAld was efficiently labeled with stable isotopes. We are currently analyzing the levels of IAAld in various IAA biosynthesis-related mutants to identify the IAA biosynthetic pathway involving IAAld.