Abstract
Auxins are signaling molecules that have critical roles in intercellular communication in plants. Indole-3-acetic acid (IAA) is the main auxin regulating plant growth and development, yet its biosynthetic pathway remains unclear. We have been dissecting the IAA biosynthetic pathway by LC-MS/MS analysis of proposed IAA precursors. We recently found that Arabidopsis has a unique IAA biosynthetic pathway branching from a crucifer-specific secondary metabolism. The YUCCA and indole-3-pyruvate pathways are proposed as common IAA biosynthetic routes in plants. Phenylacetic acid (PAA) has been known as a naturally occurring auxin, but not much is know about physiological role of PAA in plants. To better understand auxin-mediated regulation of plant growth and development, we dissected the biosynthetic and metabolic pathways for PAA. By LC-MS/MS analysis of PAA and its possible metabolites in IAA biosynthesis-related mutants, we found that YUCCA genes contribute to PAA biosynthesis in Arabidopsis. Moreover, we demonstrated that GH3 genes encoding IAA-amido synthases are implicated in PAA metabolism. Possible biosynthetic and metabolic pathways for PAA in plants will be discussed.
