Diatoms are eukaryotic, unicellular algae that produce intricately nanopatterned silica-based cell walls termed biosilica. Diatoms contain highly modified proteins termed silaffins, that are involved in biosilica formation in a poorly understood way. Silaffin sequences possess no specific domains and are not conserved between diatom species and little is known about their post-translational modifications (PTMs). Some of their lysine residues are modified by compositionally heterogeneous polyamine chains - this modification only occurs in diatoms. However, exact localization of polyamines, their molecular composition and function remain unknown. In this project we pursue two specific aims: first, we would like to characterize the biosilica-associated proteome in three closely related, but morphologically distinct diatom species (Thalassiosira pseudonana, T. oceanica, Cyclotella cryptica). Second, we develop a generic method to discover and quantify the full spectrum of polyamine modifications, including their location at the sequences of biosilica associated proteins and elucidate their role in biosilica morphoigenesis.
The project is supported by the FOR 2038 “Nanopatterned Organic Matrices in Biological Silica Mineralization” awarded by Deutsche Forschungsgemeinschaft (DFG).