Understanding the mechanisms of polarization and patterning of cells, tissues and organs is a central goal for developmental biologists. Embryos of angiosperms develop when they are still enclosed in the maternal tissue, which renders cellular, molecular and physiological analyses a technical challenge. In contrast, embryogenesis of oogamous brown algae has contributed considerably during more than a century to the study of early patterning and differentiation in plant systems as it has important advantages. Harvesting eggs and sperm is easy and leads to large populations of synchronous developing cells outside of the maternal tissue. Moreover, the large size of the eggs makes visualization of the internal structures and experimental manipulation of the zygotes more easy. Nowadays brown algae are of special interest, because they are one of the only three eukaryotic lineages besides the Viridiplantae and animals which have independently evolved a complex parenchymatous multicellular growth mode, involving meristems dividing in three dimensions.
The model species used mostly belong to the genera Fucus and Silvetia. The difficulty of culturing these fucoid algae under laboratory conditions throughout their life cycle leads to the inevitable loss of any isolated mutant and impedes extensive use of genetics in this line of developmental research. In contrast, the oogamous parenchymatous Dictyota dichotoma has been cultured for decades. Our research aims to get deeper insights in the polarization mechanisms and the evolvability of early development in plant systems using Dictyota as our model system. The choice of Dictyota opens up the perspective to apply genomics, transcriptomics and genetic analyses.
We are currently studying the polarization process producing the apical-basal pattern of zygotes of Dictyota dichotoma in order to compare with the embryology of fucoid algae and other model systems.