The growth regulator auxin is involved in all key developmental processes in plants. A
complex network of a multiplicity of potential auxin biosynthetic pathways as well as transport, signalling plus conjugation and deconjugation lead to a complicated system of auxin function. This raises the question how such a complex and multifaceted system producing such a powerful and important molecule as auxin can be effectively organised and controlled. Here we report that a subset of auxin biosynthetic enzymes in the TAA/YUC route of auxin biosynthesis is localised to the endoplasmic reticulum (ER). ER microsomal fractions also contain a significant percentage of auxin biosynthetic activity. This could point toward a model of auxin function using ER membrane location and subcellular compartmentation for supplementary layers of regulation. Additionally we show specific protein-protein interactions between some of the enzymes in the TAA/YUC route of auxin biosynthesis
