EVOLUTION OF FRUIT DEHISCENCE IN BRASSICACEAE – EXAMPLES FROM AETHIONEMA AND LEPIDIUM

Abstract

Most species of the Brassicaceae develop fruits in which seeds are released through a process termed fruit dehiscence. To provide a phylogenetic perspective for fruit dehiscence, the Arabidopsis model system will be widened here by two other systems from Brassicaceae. Some genera in Brassicaceae develop indehiscent fruits that do not release ripe seeds. The genus Lepidium comprises closely related species with either dehiscent (e.g., Lepidium campestre) or indehiscent fruits (e.g. L. appelianum). Recent phylogenies based on molecular data suggest that indehiscent fruits evolved several times independently in different clades from dehiscent fruits. The genus Aethionema is the sister group to all other extant Brassicaceae. Some species of Aethionema are heterocarpic, meaning that they develop both dehiscent and indehiscent fruits within the same infructescensce. Thus, both Lepidium and Aethionema represent interesting model systems to investigate the evolution of fruit dehiscence. Molecular genetic studies on fruit dehiscence and indehiscence in the model system Arabidopsis have been used to define candidate genes which might play a role in forming indehiscent fruits in Lepidium and Aethionema. Understanding the mechanisms involved in the transformation of dehiscent into indehiscent fruits in the same infructescence (Aethionema) and in closely related species (Lepidium) could provide general insights into the evolution of morphological traits in the Brassicaceae and beyond.