Cell differentiation controls iron assimilation in the choanoflagellate <i>Salpingoeca rosetta</i>

This study examines how cell differentiation in a choanoflagellate enables the uptake of iron, an essential nutrient. Choanoflagellates are widespread, aquatic microeukaryotes that are the closest living relatives of animals. Similar to their animal relatives, we found that the model choanoflagellate, <i>S. rosetta</i>, divides metabolic functions between distinct cell types. One cell type uses an iron reductase to acquire ferric colloids, a key source of iron in the ocean. We also observed that <i>S. rosetta</i> has three variants of this reductase, each with distinct biochemical properties that likely lead to differences in how they reduce iron. These reductases are variably distributed across ocean regions, suggesting a role for choanoflagellates in cycling iron in marine environments.