Despite coordinating incredible morphological complexity, developmental patterning is remarkably robust. My lab is interested in uncovering the properties that allow complex biological processes, like development, to occur so reproducibly.
One particularly attractive system in which to explore these ideas is the production of flat leaf architecture. The leaves of many species emerge from the stem cell niche as radially symmetric bumps, then have to develop into long and wide, but very shallow, structures. Leaves have solved this difficult biological problem by using the boundary between their dorsal and ventral sides as a guide to orient their growth. As such, ensuring the dorsoventral axis is rigorously specified and maintained is key to the robust nature of flat leaf production. My lab aims to exploit the complex, gene regulatory network underlying dorsoventral patterning to assess the determinants – and their interactions – that lead to robust developmental outcomes in multicellular organisms.
A parallel but overlapping project involves the CLASS III HOMEODOMAIN LEUCINE ZIPPER (HD-ZIPIII) proteins, which are key determinants of dorsal fate. This ancient family of transcription factors appeared around the inception of multicellularity and were repeatedly co-opted to drive several evolutionarily-important innovations, including flat leaf production. In addition to DNA-binding and dimerization domains, HD-ZIPIII proteins contain a StAR-related transfer (START) domain, raising the intriguing possibility that HD-ZIPIII activity may be under direct control of a lipophilic ligand, much like nuclear receptors in animal systems. Identifying this ligand and characterizing its molecular effects on these essential developmental regulators are central goals of my lab. We will also situate the unique properties conferred by START-mediated ligand-regulation within the rich evolutionary history of the HD-ZIPIII proteins.