Emiliania huxleyi AWI1516 Transcriptome

Coccolithophores are globally abundant, calcifying microalgae that have profound effects on marine biogeochemical cycles, the climate, and life in the oceans. They produce scales made of CaCO3 called coccoliths, which may contribute to their ecological success. The complex yet reproducible shapes of the calcite crystals within coccoliths are inspiring applications in materials science. Despite their importance, we know little about the cellular machinery underpinning coccolithophore biology. Working in the model species Emiliania huxleyi, a globally distributed bloom-former, we deploy a range of proteomic strategies to identify calcification-related proteins. These analyses are underpinned by a new E. huxleyi genome, with gene models derived from long-read transcriptome sequencing, which revealed many novel proteins specific to the calcifying clades of the haptophytes. Our experiments provide insights into the proteins involved in ion transport, coccolith vesicle development, coccolith maturation, coccolith associated polysaccharide synthesis and coccolith exocytosis. We also discover how the calcification program responds to low calcium, and gain insights into the mechanisms underlying the lack of calcification in a mutant.