Speaker: Dr. Yurika Ujiie, Marine Core Research Institute, Kochi University [website]

Seminar Title: Single-cell RNAseq approaches of shell-bearing foraminifers provide new insights into understanding marine ecology and evolution

Abstract:

Marine protists and their diversity underpin life and ecosystems in the ocean. Foraminifera are crucial players in global biogeochemical cycles due to a large amount of calcium carbonate production and harboring endosymbionts over their wide distribution ranges from the coast to the pelagic oceans. However, genetic information has been limited to few genes (i.e., ribosomal DNA) as same as other marine protists. Our understanding for molecular mechanisms, which are involved in biological activity and interactions with environments, is so far missing. We have recently developed a single-cell RNAseq approach to compare different cellular conditions of foraminifers and succeeded to predict the entire molecular mechanisms of foraminiferal calcification for the first time. Foraminifers actively use calcium-ion (Ca²⁺) with Ca²⁺trafficking system during calcification and excrete excess Ca²⁺ across the plasma membrane. At the same time, the enzyme α-carbonic anhydrase (CA) induces the generation of bicarbonate and proton from multiple CO₂ sources. The CA genes have evolved in foraminifers independently from other calcifying organisms such as corals and mollusks. Our findings provide not only unknown insights into the calcification mechanisms but also future subjects to address the functional changes of calcification-related genes in the wake of global warming and ocean acidification. A single-cell RNAseq approach is widely applicable to examine cellular responses to environmental stimulations and to address endosymbiotic activity in such foraminiferal metabolisms.