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Abstract

Brown algae belong to the stramenopiles and as such are phylogenetically distant from plants, animals and fungi. They are one of only five eukaryotic lineages that have evolved independently to develop into complex multicellular organisms. To contribute to the understanding of developmental processes that lead to the observed complex multicellularity in brown algae we have analysed Ectocarpus siliculosus both by scanning and transmission electron microscopy. We have compared morphologically the wild-type and a mutant that shows defects in the first cell divisions of the developing organism. Potential differences in Golgi morphology were analysed in datasets obtained by focused-ion beam scanning electron microscopy of plastic embedded samples of both the wild-type and the mutant. As higher plants and other algae, brown algae are photosynthetically active thereby reducing carbon dioxide from the atmosphere. The chloroplast of brown algae originated from a secondary endosymbiosis event in contrast to chloroplasts from land plants. In order to obtain a better understanding of the molecular mechanisms involved in photosynthesis, we started to explore these processes structurally in Ectocarpus.