Evolutionary developmental biology of fruits and flowers in Brassicales

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Despite our fascination with the diversity of forms observed in flowering plants, our understanding of how this variation has arisen is limited. Ultimately, we would like to know how changes in gene regulation have lead to morphological differences - a key question in biology. The goal of my research is to elucidate mechanisms underlying variation in two important traits: fruit structure and floral form. Detailed knowledge of fruit developmental genetics and evolution is essential because seed dispersal represents a key component of plant fitness. Moreover, the dispersal of crop plants and controlling the gene flow in genetically modified crop systems, and the increasing prevalence of introduced species in natural ecosystems necessitate a more complete picture of how different types of seed packaging have originated. Despite this relevance, there are few evolutionary developmental studies on fruits, instead most studies focus on another ecologically important feature of plants - the flower. Floral traits are clearly important for pollinator interactions, yet there is a notable gap in our knowledge of the genetic basis of features that influence pollinator behavior. **I focus on two groups that exhibit variation in these traits and that represent exemplary systems to investigate fruit and floral evolution. A group within the mustard family (Brassicaceae), called the Brassiceae, is important because it includes crop species (e.g., canola, broccoli) and because the fruits are often segmented, a trait that dramatically alters how their seeds are dispersed. This complex structure has evolved multiple times, leading to the fundamental question of whether the same genetic pathway has been recruited similarly in independent evolutionary events. Unlike its sister family Brassicaceae, members of Cleomaceae have many different types of flowers, facilitating the examination of features important for pollinators. Our previous investigations unveiled a different, but no less fascinating, pattern in this group. Similar mature flowers have two distinct developmental trajectories. Thus, we can address another important question: do these two patterns reflect variable genetic bases? Genetic studies are greatly facilitated because these two groups are both closely related to the genetic plant model, Arabidopsis, and because a wealth of genomic resources is being built in both families.**In this proposal, I take a comprehensive approach that fuses multiple fields and will lead to substantial advancements in our understanding of plant evolution. First, my group will conduct detailed developmental studies on a range of species. This traditional approach provides essential data on how the mature form is achieved, which in turn leads to hypotheses on what genes may be responsible for morphological differences when combined with genetic knowledge from model species. A thorough picture of how traits have changed through time in these lineages emerges when we incorporate information about how species are related to one another. Substantial effort will be spent determining when and where genes of interest are expressed. These studies have been shown to be immensely valuable for correlating a particular morphology with a gene expression pattern, thus providing insight into how genetic pathways may be altered to generate morphological innovations. That is, different expression patterns across species with morphological differences suggest that gene may have a role in generating the observed variation. Finally, my program will move beyond correlation by conducting experiments that directly test how these genes function in our focal plants, which represent critical data often lacking in evolutionary studies.