Elucidating the Structure-Function Relationship in Silicanins and their Role in Diatom Silica Formation

• Applicant: Professor Dr. Nils Kröger
• Subject Area: Plant Physiology ; Plant Biochemistry and Biophysics ; Structural Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 561133711

Organisms are amazingly adept in producing inorganic materials with complex morphologies and extraordinary properties through genetically controlled mechanisms (biomineralization). How the encoded proteins and other biomolecules control mineral morphogenesis beyond the nanometer scale over several orders of magnitude is poorly understood. Biomineralization by diatoms, a large group of unicellular microalgae that produce intricately nano- and micropatterned silica cell walls (5-500 µm in size), are model systems to study the fundamental mechanisms of biomineralization. Silica formation in diatoms and all other silica forming protists occurs within a specialized intracellular compartment called the silica deposition vesicle (SDV), and involves a large family of transmembrane proteins, known as silicanins. Using in vivo and in vitro assays, the Kröger group provided strong evidence that silicanin-1 controls silica morphogenesis through the formation of supramolecular clusters and the interaction with generic components of diatom biosilica termed long-chain polyamines (LCPAs). Using in silico structural models, the Zarivach group has predicted interactions between the cytoplasmic tail of silicanin-5 with dAnk1 and dAnk3, which are proteins controling the formation of pore patterns in diatom silica. Gene knockout experiments and in vitro binding assays have partially validated the in of the Biosilicasilico predictions. We hypothesize that silica morphogenesis is governed by phase separation processes based on the spatially and temporally coordinated assembly of protein interaction networks at the SDV membrane, with silicanins and dAnks as key components. To investigate this hypothesis, we will integrate molecular genetic and biochemical approaches as well as structure determination and modeling. This will enable us to predict and experimentally validate structural features that determine silicanin function, and test the current model on phase separation-mediated biosilica morphogenesis. Our research will provide deep insight into the structure-function relationship in silicanins and shed light on the mechanisms by which they control biosilica morphogenesis in the SDV of diatoms and other silica forming organisms.

• DFG Programme: Research Grants
• International Connection: Israel
• Partner Organisation: The Israel Science Foundation
• Cooperation Partner: Professor Dr. Raz Zarivach