Cell differentiation controls iron assimilation in a choanoflagellate

Area of Science:

• Marine microbiology
• Eukaryotic evolution
• Biogeochemical cycles

Background:

• Marine microeukaryotes exhibit diverse life histories linked to their environment.
• Understanding microeukaryote ecological functions is crucial for biogeochemical cycles.
• Choanoflagellates, as phagotrophs, offer models for nutrient cycling and life history transitions.

Purpose of the Study:

• Investigate how cell differentiation in *Salpingoeca rosetta* impacts nutrient utilization.
• Identify the molecular mechanisms behind iron acquisition in specialized choanoflagellate cell types.
• Explore the ecological significance of choanoflagellate iron utilization in marine environments.

Main Methods:

• Analysis of gene expression in *Salpingoeca rosetta* during differentiation.
• Identification of orthologous genes in other eukaryotes, including mammals.
• Correlation analysis of *cytb561a* transcript abundance with oceanic metagenomic data and upwelling events.

Main Results:

• Cell differentiation in *S. rosetta* leads to expression of cytochrome b561 iron reductase (*cytb561a*).
• This enzyme facilitates the utilization of insoluble ferric colloids for improved growth.
• *cytb561a* transcripts correlate with marine upwellings, a source of ferric colloids.

Conclusions:

• Choanoflagellate cell differentiation enables the use of previously inaccessible iron sources.
• Phagotrophic eukaryotes like choanoflagellates play vital roles in cycling ferric colloids.
• These findings shed light on early animal evolution and the development of multicellularity.