Structural Biology of Nuclear Auxin Action

Auxin coordinates plant development largely via hierarchical control of gene expression. During the past decades, the study of early auxin genes paired with the power of Arabidopsis genetics have unraveled key nuclear components and molecular interactions that perceive the hormone and activate primary response genes. Recent research in the realm of structural biology allowed unprecedented insight into: (i) the recognition of auxin-responsive DNA elements by auxin transcription factors; (ii) the inactivation of those auxin response factors by early auxin-inducible repressors; and (iii) the activation of target genes by auxin-triggered repressor degradation. The biophysical studies reviewed here provide an impetus for elucidating the molecular determinants of the intricate interactions between core components of the nuclear auxin response module.

TrendsAuxin governs plant development via gene expression controlled by a few nuclear components. Auxin-promoted assembly of SCFTIR1/AFB complexes recruits AUX/IAA repressors for proteolysis, causing derepression of ARF activators and gene induction via auxin-responsive DNA elements.Structural biology has gained enormous momentum and the first high-resolution models allow unparalleled insights into DNA recognition by ARFs, into interaction modes of AUX/IAAs with ARFs and corepressors, and into auxin-triggered AUX/IAA degradation.It has increasingly becoming clear that the key players are embedded in complex molecular networks of post-translational modifications and interactions with various ligands that provide multiple nodes for signal integration and response specification.The biophysical approach will firmly expand and refine our understanding of the auxin response pathway beyond the nuclear core module, which will be tested by synthetic biological studies in planta and in heterologous in vivo systems.