Exploring the cellular mechanisms that control cell shape formation, nuclear migration and chloroplast adaptations to environmental conditions in algae and higher plants

This habilitation deals with several aspects of plant cell development and adaptation to environmental conditions. An array of organisms including unicellular algae, macroalgae and higher plants have been investigated. The topics discussed encompass cell shape formation, nuclear migration, and ecological adaptation to unique environmental situations. Despite the different scientific questions investigated, the focus of these studies has remained on cell biological phenomena. Insight into these complicated topics are the result of extensive studies at the subcellular level as well as physiological investigations. The major topics include cytoskeleton dependent cell shape formation, nuclear migration, chloroplast protrusion formation and the adaptation strategies to UV irradiation and environmental conditions. The “red line” through this habilitation and connection of all the original works included is given by a cell biological point of view on the various topics. From these studies emerge interesting similarities between algal and higher plant cytoskeleton and links between algal and higher plant chloroplast adaptations. In order to obtain a comprehensive understanding of the common structural and physiological phenomena overarching this cell biological theme it becomes clear that this can only be obtained by investigating a variety of organisms. Specialized microscopic techniques, which will be referenced to throughout this habilitation, include advanced time-lapse video light microscopy, confocal laser scanning microscopy (CLSM) and electron microscopy. For observation of live cells a special temperaturecontrolled chamber (LM-TCC) has been designed and constructed. Transmission electron microscopy (TEM) has been carried out and samples have been prepared either by chemical fixation or by high pressure freeze fixation followed by freeze substitution. Specialized subcellular staining protocols including immunodetection- and immunolocalization have been used. In some cases, live cells have been microinjected or manipulated by optical tweezers. In addition scanning electron microscopy (SEM), cryo SEM or environmental scanning electron microscopy (ESEM) have been performed.