Odyssey of auxin

The history of plant biology is inexorably intertwined with the conception and discovery of auxin, followedby themany decades of research to comprehend its action during growth and development. Growth responses to auxin are complex and require the coordination of auxin production, transport, and perception. In this overview of past auxin research, we limit our discourse to the mechanism of auxin action. We attempt to trace the almost epic voyage from the birth of the hormonal concept in plants to the recent crystallographic studies that resolved the TIR1-auxin receptor complex, the first structural model of a plant hormone receptor. The century-long endeavor is a beautiful illustration of the power of scientific reasoning and human intuition, but it also brings to light the fact that decisive progress is made when new technologies emerge and disciplines unite. The simple hormone related to tryptophan,indole-3-acetic acid (IAA or auxin), has probably been the most intensely studied mole-cule in plants as it impacts virtually every facet during their life cycle. In fact, a total failure in IAA production has not been reported for an