Silica morphogenesis of diatoms takes place within specialized intracellular compartments, the silica deposition vesicles (SDVs), which are known to be lipid bilayer-bound compartments. Even though the SDV has not yet been isolated, a number of different silica-associated proteins and other biomacromolecules (silaffins, silacidins, long chain polyamines, cingulins, silicanins, and chitin) have been identified that are potential candidates of the SDV. These biomacromolecules are permanently associated with biosilica, accelerate silica deposition, and influence silica morphogenesis in vitro. Different models have been proposed to explain the nano- and micropatterning of the formed silica. However, the fact that biosilica morphogenesis takes place in intimate contact with SDV membrane has, surprisingly, not yet been considered as a structural determinant for silica formation. To close this gap, this project aims to investigate the impact of lipid bilayers that mimic SDV membranes on biomolecule induced silica morphogenesis. For this purpose, it is planned to analyze the SDV membrane lipid composition in cooperation with external and Nanomee partners.
The full complexity of silica patterns may not only be a function of the self-organization of the biomolecules associated with biosilica, but may also be influenced by laterally mobile lipids of the SDV. Therefore, we will also investigate how different classes of biosilica-associated biomolecules interact with lipid membranes, how the membrane interaction changes their structures, and how they self-organize under the influence of a membrane. We will further analyze the membrane’s influence on the self-assembly of the silica forming biomolecules, and on silica morphogenesis. Our focus will be on silicanin-1 (Sin1), a transmembrane protein which was recently discovered by our Nanomee partners and that was found to be associated to the SDV membrane and resulting biosilica. Its reconstitution into artificial membranes and investigation of its aggregation behavior and interaction with other bioorganic molecules are steps on the way to enlighten the role of Sin1 in silica morphogenesis.
Through in vitro reconstitution of the silica forming machinery from synthetic molecules we aim at obtaining a detailed picture of the silica morphogenesis process from the sub-nanometer to the micrometer scale taking place in intimate contact with lipid membranes.