Biological systems are outstandingly adept at information processing. A great deal is known about how cells translate signals into biologically relevant outputs, such as modifications in gene expression, protein activity, and ion fluxes.

How biological systems process information in complex and changing environments is a central unsolved puzzle of the post-genomic age.

In plants, physiology and development are inextricably linked: morphogenesis reflects external environmental conditions as much as endogenous cues. Developmental, metabolic, and environmental information is encoded, transported, and ultimately translated into phenotype through a complex network of hormones. The highly plastic Arabidopsis seedling has been an excellent system for dissecting the interaction between internal and external cues during light-directed development (photomorphogenesis). Seedling stem (hypocotyl) length is a sensitive, quantitative, readily-imaged output for studying the photomorphogenetic program.

We are currently focusing on three questions:

1. How do cells integrate information from multiple hormones? Different hormones trigger seemingly identical growth responses, yet each hormone pathway is required for normal growth. My laboratory is using a variety of tools to fully dissect the interaction between two key growth regulators—auxins and brassinosteroids.

2. How does cell fate shape hormone responses? We have uncovered a previously unsuspected role for brassinosteroids in directing cell fate and growth in the root epidermis. We are using this second cell type to elucidate how hormonal cues are modified by cell identify.

3. How are cellular growth rates modified over time? A significant limitation to current studies of photomorphogenesis is the lack of temporal and spatial control in assaying hormone/hormone and hormone/light interactions. We are combining time-lapse imaging with new tools for conditional regulation of hormone action to define and model dynamic growth signals.