Diversification of fruit shape in the Brassicaceae family.

KEY MESSAGE: Diversity in fruit shape. Angiosperms (flowering plants) evolved during the Cretaceous Period more than 100 million years ago and quickly colonized all terrestrial habitats on the planet. A major reason for their success was the formation of fruits that would protect and nurture the developing seeds. Moreover, a massive range of diversity in fruit shape occurred during a relatively short time, which allowed for the development of ingenious ways of fertilization as well as strategies for efficient seed dispersal. The Brassicaceae family more than any exemplifies the diversity in fruit morphologies, thus providing an ideal group of plants to study how specific shapes are established. Although many genes controlling fruit patterning in the model plant Arabidopsis thaliana have been identified, the processes of carpel and fruit morphogenesis are still poorly understood. Moreover, Arabidopsis fruits are relatively simple in their structure and are therefore not ideally suited for analyzing processes of morphology determination without comparison to species with differently shaped fruits. Here, we review the diversity of fruit shape within the Brassicaceae family. As an example we describe the close relative of Arabidopsis, Capsella rubella that develops flat, heart-shaped fruits showing and highlighting its potential as a model system for research into organ shape. Recent progress in genomics including fast and cheap genome sequencing and annotation as well as development of mutant populations has opened entirely new and exciting possibilities of studying the mechanisms and processes underlying fruit formation in angiosperms.