Proteomic analysis of the coccolith forming compartment in Pleurochrysis carterae and identification of protein components involved in calcite morphogenesis

• Applicant: Professor Dr. André Scheffel
• Subject Area: Plant Biochemistry and Biophysics ; Plant Physiology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452716909

Coccolithophores are unicellular marine algae with a cell wall made up by intricately-shaped calcified scales known as coccoliths. Each coccolithophorid species exhibits its own characteristic coccolith morphology. The coccoliths consist of calcite (CO3) crystals, which often show species-specific and complex morphologies. Coccolith biogenesis occurs in an intracellular compartment called coccolith vesicle. One of the major unsolved question in biomineralization research is how the characteristic shapes and nanostructures of microbial biominerals are achieved. The recent successful development of a protocol for the genetic transformation of the coccolithophore P. carterae has now opened up the possibility of elucidating key components and mechanistic principles of coccolithophore calcite morphogenesis in vivo. So far, however, no P. carterae genes have been linked with coccolith morphogenesis. In this research project, we will isolate and proteomically characterize coccolith vesicles of P. carterae to identify the proteins of the coccolith vesicle membrane. In silico analysis of these proteins will reveal candidate morphogenetic proteins for functional analysis in vivo. The intracellular localization of these candidates will be studied by fluorescence microscopy to verify their coccolith vesicle association. To analyse candidate morphogenetic proteins in vivo we will develop and apply (1) an improved transgene expression tool for P. carterae, which facilitates strong overexpression of transgenes, and (2) the CRISPR–Cas9 gene-editing tool to generate knockout mutants. This project will enhance our understanding of biomineral morphogenesis and broaden the repertoire of genetic tools for elucidating the molecular basis of the intriguing physiological capabilities of coccolithophores.

• DFG Programme: Research Grants