The role of lipids for the establishment of the peribacteroid membrane in root nodules and the periarbuscular membrane during mycorrhiza formation in Lotus japonicus

• Applicant: Professor Dr. Peter Dörmann
• Subject Area: Plant Physiology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550485493

Plants of the Fabaceae family (legumes) are important protein crops and are characterized by their capacity to establish symbiotic interactions with nitrogen-fixing rhizobial bacteria in root nodules. Legume species can furthermore establish interactions with mycorrhizal fungi to enhance the uptake of macronutrients like phosphate. In both symbiotic interactions, high amounts of extra membranes are required to establish the peribacteriod membrane (PBM) encapsulating the rhizobial bacteria, and the periarbuscular membrane (PAM) surrounding the fungal arbuscules within the cytosol of the host cell. As all nutrients and signaling molecules need to pass the membrane barrier between host and symbiont, the lipids in the PBM and PAM are presumed to be of high relevance for the establishment of symbiosis. We previously identified the galactolipid digalactosyldiacylglycerol (DGDG) in the PBM, and it was later shown that DGDG is important for the development of nitrogen fixing nodules. However, the exact lipid composition of the PBM remained unknown, and it is still unknown, whether DGDG also plays a role in the PAM. In addition, it is unclear which DGDG synthase genes are relevant for DGDG production during nodulation or mycorrhiza formation. We will measure the major lipid classes (glycerolipids, sphingolipids, sterol lipids) in the PBM using modern lipidomic approaches. We identified three DGDG synthase genes in the model legume Lotus japonicus, and we isolated insertional mutants for all three genes. We will decipher the roles of the different DGDG synthases for DGDG production during nodulation and mycorrhiza formation. We will finally unravel whether DGDG also plays a role during PAM formation, and whether DGDG is important of mycorrhiza establishment.

• DFG Programme: Research Grants