The Genetic and Molecular Basis of Flower Development in Arabidopsis

My laboratory studies pattern development in flowers, concentrating on two basic patterns that develop in parallel. The first is the pattern of organ number and position. The flowers of the plant we study, the mustard Arabidopsis thaliana, have a total of 16 organs: four organs in the first organ whorl, with a 90-degree angle between adjacent organs, four organs inside and alternate to the first whorl organs, six third-whorl organs with their own characteristic spacing and divergence angles, and two fourth-whorl organs (Müller, 1961; Smyth et al., 1990). This number and position of floral organs is specific to members of the mustard family and close relatives; other families have quite different patterns of organ number and position. The second pattern, which develops to a large degree independently of the first, is the pattern of organ identity. From the outside to the inside of the flower, one finds the four organ types sepal, petal, stamen, then carpel occurring in this order in successive organ whorls. This radial order of organ identities is not at all family-specific, being almost completely uniform in flowering plants. We would like to understand how the activities of specific genes produce both patterns in developing floral primordia, to understand how these patterns have arisen in the evolution of flowering plants, and to know what differences in the genes that control these patterns give the diversity of flower forms that exists in nature