Unique evolution of foraminiferal calcification to survive global changes

Area of Science:

• Biogeosciences
• Marine Biology
• Cell Biology

Background:

• Foraminifera are ancient, calcium carbonate-producing eukaryotes vital to biogeochemical cycles and environmental monitoring.
• Understanding foraminifera calcification mechanisms is limited, hindering predictions of their response to ocean acidification.
• Ocean acidification impacts marine calcium carbonate production and global biogeochemical cycles.

Purpose of the Study:

• To elucidate the molecular mechanisms of calcification in foraminifera.
• To investigate how foraminifera regulate intracellular calcium and carbon dioxide for shell formation.
• To understand the evolutionary basis of foraminifera calcification in response to environmental changes.

Main Methods:

• Comparative single-cell transcriptomics to identify relevant genes.
• Fluorescent microscopy to visualize cellular processes during calcification.
• Analysis of calcium ion (Ca2+) transport and alpha-carbonic anhydrase gene functions.

Main Results:

• Identified specific calcium ion transport/secretion genes and alpha-carbonic anhydrases controlling foraminifera calcification.
• Demonstrated active calcium ion uptake for mitochondrial ATP synthesis and excess calcium pumping to prevent cell death.
• Revealed unique alpha-carbonic anhydrase genes facilitating bicarbonate and proton generation from multiple CO2 sources.

Conclusions:

• Foraminifera possess sophisticated, independently evolved mechanisms for calcification since the Precambrian.
• These mechanisms allow for large cell development and calcification despite decreasing seawater calcium and pH.
• Findings provide crucial insights into foraminifera's ability to endure ocean acidification.