Although plant cells are encased in rigid cell walls and are therefore incapable of the types of developmental migrations which take place in animal systems, it is clear from genetic studies that the fate of individual plant cells is dependent on cell-cell communication rather than being the product of an invariant cell lineage. We are interested in determining what sorts of molecular mechanisms are used in these cellular interactions and how they are used to regulate the developmental process. We are using two different experimental systems in the small weed Arabidopsis thaliana to address these questions.

During reproduction in Arabidopsis, pollen grains land on the stigma, germinate and grow pollen tubes which penetrate the stigma surface and are guided to the ovules. This growth and development of the male gametophyte is controlled by cellular interactions with the female reproductive system. We are interested in identifying genes which are essential to these communication processes by isolating mutations which disrupt the growth and development of the male gametophyte. Using this approach it has been possible to identify a number of different genes involved in various cellular interactions which we are characterizing further.

The second system which we are studying is a family of genes which control the cellular interactions which take place between epidermal cells in Arabidopsis. These genes have been identified by mutations which result in fusion events taking place between the surfaces of organs which in wild-type plants would remain distinct. These genes normally act to regulate this fusion process, in part by controlling the ability of signaling molecules to cross the cuticle found on the outer surface of the plant. Experiments in the lab are directed toward better characterization of these genes and their phenotypes, including cloning and molecular characterization of the genes themselves.