REOX · Reconstructing the origin of the auxin response system

Hormone signaling allow organisms to regulate their physiology. Single hormones trigger multiple and complex, context-dependent responses that evolved from simpler, ancestral pathways. A key, unanswered question is what functions were initially regulated by these ancestral pathways. In plants, auxins are key hormones that regulate multiple processes throughout the life-cycle. The three-components auxin signaling system is an excellent model of a simple pathway that generates a complex response, but it is unclear how this system has evolved. In the REOX project, I will use Charophycean algae that contain only a partial auxin response system, to reconstruct the evolutionary trajectory that allowed the emergence of the first auxin response pathway. I will study the structure, function and regulation of the closest algal orthologs of the plant transcriptional regulatory proteins, the ARFs. I will next synthetically revive the ancestral components of the pathway and assemble these into a functional response system in algae. With this, I expect to reveal the ancestral function of the auxin response system, and reconstruct the evolutionary trajectory towards hormone action in land plants. I expect this project to inspire similar strategies in the molecular evolution field. From a training point of view, this fellowship will build on my expertise on evolutionary genetics and molecular biology and allow me to complement these with skills in protein biochemistry and algal biology. This will prepare me for a future in studying evolution at different levels of complexity (molecular to ecological), and will boost my opportunities to reach an independent academic research position in this field. In summary, this projects aims to advance our understanding on the origin of hormone signalling and response evolution, and render a well-trained academic researcher with the capacities needed to develop a professional career within evolution research.