Membrane Lipids, Waxes and Oxylipins in the Moss Model Organism Physcomitrella patens

The moss Physcomitrella patens receives increased scientific interest since its genome was sequenced a decade ago. As a bryophyte, it represents the first group of plants that evolved in a terrestrial habitat still without a vascular system that developed later in tracheophytes. It is easily transformable via homologous recombination, which enables the formation of targeted loss-of-function mutants. Even though genetics, development and life cycle in Physcomitrella are well studied nowadays, research on lipids in Physcomitrella is still underdeveloped. This review aims on presenting an overview on the state of the art of lipid research with a focus on membrane lipids, surface lipids and oxylipins. We discuss in this review that Physcomitrella possesses very interesting features regarding its membrane lipids. Here, the presence of very-long-chain polyunsaturated fatty acids (VLC-PUFA) still shows a closer similarity to marine microalgae than to vascular plants. Unlike algae, Physcomitrella has a cuticle comparable to vascular plants composed of cutin and waxes. The presence of VLC-PUFA in Physcomitrella also leads to a greater variability of signaling lipids even though the phytohormone jasmonic acid is not present in this organism, which is different to vascular plants. In summary, the research on lipids in Physcomitrella is still in its infancy, especially considering membrane lipids. We hope that this review will help to promote the further advancement of lipid research in this important model organism in the future, so we can better understand how lipids are involved in the evolution of land plants.