At the heart of my research interests lies the idea that molecular resources and techniques are important tools for connecting evolution at the gene and genome level to the developmental processes that produce variant morphologies for selection to act upon.
My dissertation will focus on investigating the evolution of female gametophyte (the haploid, egg-producing structure within the life cycle of a plant) development in flowering plants. Flowering plants have specialized female gametophytes that contain two separate targets of fertilization ñ a haploid egg cell that gives rise to an embryo (the next diploid generation) and a central cell that becomes endosperm, the nutritive tissue that will fuel early embryonic growth. Until three years ago, nothing was known about the genetic or molecular basis for female gametophyte development in flowering plants. However, an article published in Science last year characterized an auxin gradient during early female gametophyte development of the model plant Arabidopsis thaliana. The manipulation of that auxin gradient resulted in supernumerary egg cells and other aberrant cell specifications. This led to the hypothesis that the local synthesis of auxin, a ubiquitous plant hormone that is central to most developmental processes in plants, produces a morphogenetic gradient as part of a homeotic mechanism for cell specification within the female gametophyte.
What remains to be seen is 1) how widely applicable this model is across the diversity of flowering plants and 2) whether this model can accommodate the development of female gametophytes in which mature morphology differs from that of A. thaliana. For my dissertation, I plan to address these questions by targeting auxin biosynthesis genes and characterizing their sequences, copy number, and expression patterns in a selection of flowering plant taxa that occupy important phylogenetic positions and/or encompass a variety of female gametophyte morphologies. Of particular interest are taxa whose female gametophytes are composed of varying numbers of cells, yet still specify only one each of the two fertile cells types. These taxa provide an opportunity to investigate the independence of mechanisms responsible for cell number and identity, an important aspect of homeotic control.