AUXOLOGY: When auxin meets plant evo-devo

Auxin is implicated throughout plant growth and development. Although the effects of this plant hormone have been recognized for more than a century, it is only in the past two decades that light has been shed on the molecular mechanisms that regulate auxin homeostasis, signaling, transport, crosstalk with other hormonal pathways as well as its roles in plant development. These discoveries established a molecular framework to study the role of auxin in land plant evolution. Here, we review recent advances in auxin biology and their implications in both micro- and macro-evolution of plant morphology. By analogy to the term ‘hoxology’, which refers to the critical role of HOX genes in metazoan evolution, we propose to introduce the term ‘auxology’ to take into account the crucial role of auxin in plant evo-devo.

► The phytohormone auxin is deeply involved in making the plant body plan.
► Changes in auxin regulation correlate with major morphological innovations in land plants.
► Minor changes in auxin regulation could have also played a role in the morphological diversification of closely related species.
► We propose the term “AUXOLOGY” to show the importance of auxin in plant evo-devo.