Pollen grain and stigma structures are irresistibly ornate and diverse across taxa. I am curious about intra- and inter-specific variations in both structure and function (architecture and cell behaviors). By comparing pollen germination across Arabidopsis thaliana ecotypes and other taxa in the Brassicaceae, our lab has found variations in the escape routes taken by pollen tubes, as they leave the pollen grain and enter the stigma. Some erupt directly through the grain wall, while others exit through openings or apertures. We now seek to:
- characterize and quantify subtle structural and behavioral differences,
- investigate their relevance for mating success,
- reveal phylogenetic patterns in behaviors, to relate to those in structure.
To address the first research aim of characterization and quantification, I have collaborated with material scientist Steve Sibener at the University of Chicago. We have used an atomic force microscope to measure the stiffness of the pollen walls, through which the pollen tubes break, and have scored the frequency of aperture use during germination of different pollens.
For the second aim, mating success, we are collaborating with geneticist Rob Swanson at Valparaiso University in Indiana. His lab is using A. thaliana recombinant inbred lines to map female and male loci involved in nonrandom mating, while my lab is following cell behaviors during competitive crosses between ecotypes. For this, we are racing pollen tubes expressing different fluorescent proteins against one another.
For the third aim, phylogenetic patterns, we have conducted a survey of pollen germination in 32 species within the Brassicaceae, scoring the various frequencies with which pollen tubes break directly through the pollen wall.