The plant hormone auxin is involved in almost every aspect of plant growth and development. Auxin has been studied for well over a century and while many aspects of its function have been elucidated, the details of how this one molecule can coordinate so many critical responses have remained a mystery. A large facet of auxin function has been tied to its regulation of gene expression through a signaling pathway composed of only a handful of key components, each of which belongs to a large gene family. One attractive hypothesis for the diversity of auxin signaling responses is that functional divergence between signaling component family members could provide variation in response to a generic auxin signal. Thus, different component family members can be used in combination to elicit distinct responses depending on the cellular complement of components. (For more details, see the review I co-authored that was published last summer). However, this pathway is complicated by genetic redundancy and co-expression of signaling component family members, auxin trafficking, and feedback that buffer perturbations to the pathway.
To simplify matters, I worked as part of a collaborative team between the Nemhauser (Biology) and Klavins (Electrical Engineering) labs to introduce all of the components of the auxin response pathway from the plant Arabidopsis thaliana to the fungus Saccharomyces cerevisiae (Baker’s yeast). In this way, we could test and expand our understanding of how auxin signaling components work together to generate diverse responses to auxin. In our recent publication, we were an;e to show that the core auxin signaling components can reproduce auxin-induced gene expression in yeast – a feat possible thanks to the remarkable conservation of cellular machinery in eukaryotes. By applying the tenets of synthetic biology to recapitulate auxin signalling in yeast, we could systematically incorporate and vary individual components and component family members to precisely quantify the timing and performance of auxin signaling circuits. As a result, we were able to generate a new suite of tools for engineering complex synthetic systems and also gained unexpected insights into why plants can use auxin so effectively.
Check out a review here and read the most recent paper here!
