Genome and transcriptome sequencing of the coccolithophores Chrysotila carterae, Scyphosphaera apsteinii, and Calyptrosphaera sphaeroidea to study the mechanism of coccolithogenesis

• Applicant: Professor Dr. André Scheffel
• Subject Area: Plant Biochemistry and Biophysics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 458724942

Coccolithophores, a group of calcifying unicellular eukaryotic algae, are one of the dominant phytoplankton groups of the world’s oceans. They are globally distributed and play significant roles in marine ecosystems and biogeochemical cycles. Calcification, the formation of the CaCO3–based cell wall scales of these algae, is the prime geochemical impact of coccolithophores. This very important aspect of coccolithophore biology is still poorly understood. Recently, a method for the genetic manipulation of the Chrysotila carterae became available, opening up new possibilities for studying coccolithogenesis in vivo, which was not possible before. The current bottleneck for molecular genetic work on C. carterae is the lack of a genome sequence and a high-quality transcriptome. Generating these sequence resources for C. carterae and species that produce markedly different coccolith architectures, will enable the application of genomic and proteomic approaches, which are much more powerful than traditional approaches, for deciphering this complex process at the molecular level. In this research project, we will reconstruct reference genomes and transcriptome atlases of the coccolithophores Scyphosphaera apsteinii, Calyptrosphaera sphaeroidea, and the transformable species C. carterae, to remove the main bottlenecks for molecular approaches to study coccolithogenesis. The availability of these resources will greatly impact the ongoing proteomics and reverse genetics project with C. carterae in our laboratory. Furthermore, we plan totranscriptionally profile C. carterae wildtype and mutants with defects in coccolith formation, and S. apsteinii grown under conditions that alter the morphotype composition of its coccospheres, and perform comparative analyses with the goal to identify common as well as species- and clade-specific genes to associate them with specific coccolith morphologies. Moreover, we will create a pathway-centric reference database for coccolithophores from our data, to serve the scientific community. We expect this project to provide new candidate genes of the coccolithogenesis program for future studies, and valuable resources for the in-depth study of the molecular mechanisms that characterize the biology and evolution of these intriguing algae.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Dirk Walther