The project investigates how the origin of a single developmental control gene, GORDITA (GOA), by gene duplication and sequence divergence contributed to plant fitness and adaptation in the Brassicaceae. While the ancestral Bsister genes (ABS-type genes) are involved in ovule development, the derived GOA-type genes acquired a new expression domain and function in fruit development. By comprehensive comparative analyses involving GOA-type and ABS-type genes from diverse Brassicales species we will investigate when the lineage that led to extant GOA-type genes originated, and by which molecular mechanisms these genes acquired their unique expression patterns, domain structures, and function during fruit development. To better understand how the ancestors of GOA escaped ‘Ohno’s dilemma’ we will analyze the molecular evolution in the different branches of Bsister genes during the phylogeny of Brassicales employing in silico methods. Using protein-protein interaction studies we will investigate how changes in the protein structure changed the protein interaction network of GOA in comparison of ABS. To assess how the origin of GOA-type genes contributed to the adaptation of Brassicaceae species we will determine proxies of plant fitness under greenhouse conditions using transgenic knock-out plants, and will do preparative work for future determination of plant fitness under natural growth conditions using non-transgenic mutants.