LD Plasma membrane contact site is conserved across Angiosperm Lineage

In seed plants, a tethering complex of two proteins, SEED LIPID DROPLET PROTEIN (SLDP) and LIPID DROPLET PLASMA MEMBRANE ADAPTOR (LIPA), binds lipid droplets (LDs) to the plasma membrane (PM). While the physiological function remains obscure, the conservation of the process is strong. The tethering of LDs can be observed broadly in a variety of seed plants seedling tissues. Interestingly a tethering might not be limited to the PM and could be associated with other organelles in other plants. Here, we show that LIPA and SLDP have emerged in the early period of land plant evolution likely before the emerging seed plants became dominant. They are, however, most prominently conserved in seed plants and their homologs share the tethering function in ectopic expression systems. This interaction is robust and can even be functional across taxon boundaries. The evolution of a LD PM tether in that significant time point also puts the LD in focus of land plant evolution. The involvement of LDs in conquest of terrestrial ecosystems and the studying thereof can give valuable insight in physiological processes that made early terrestrialization events possible. Further studies need to evaluate the function of the discovered homologs in non-seed plants.