The Munich screen for Arabidopsis embryo patterning genes.

The capacity of the zygote to generate an embryo containing many differentiated tissues has fascinated biologists for centuries. Initially, most experimental embryology involved transplantation experiments or biochemical assays using animal species with large eggs. Starting in the 1980s, large scale genetic screens were used to understand embryogenesis of the fruit fly Drosophila melanogaster. Subsequently, David Meinke demonstrated the utility of the plant Arabidopsis thaliana for studies of embryo and seed development and initiated an extensive collection of embryo defective mutants. Inspired by the success of saturation mutagenesis screens in the Drosophila embryo and by the ease of genetic analysis in Arabidopsis, Gerd Jürgens and colleagues performed a large-scale genetic screen to identify genes that pattern the Arabidopsis embryo (Mayer et al., Nature, 1991). These brute force genetic screens had a profound effect on the field, illustrating the power of genetics for the study of plant embryology and emphasizing differences between plant and animal embryogenesis.