Association of Phosphatidylinositol-Specific Phospholipase C with Calcium-Induced Biomineralization in the Coccolithophore Emiliania huxleyi

Abstract

Biomineralization by calcifying microalgae is a precisely controlled intracellular calcification process that produces delicate calcite scales (or coccoliths) in the coccolithophore Emiliania huxleyi (Haptophycea). Despite its importance in biogeochemical cycles and the marine environment globally, the underlying molecular mechanism of intracellular coccolith formation, which requires calcium, bicarbonate, and coccolith-polysaccharides, remains unclear. In E. huxleyi CCMP 371, we demonstrated that reducing the calcium concentration from 10 (ambient seawater) to 0.1 mM strongly restricted coccolith production, which was then recovered by adding 10 mM calcium, irrespective of inorganic phosphate conditions, indicating that coccolith production could be finely controlled by the calcium supply. Using this strain, we investigated the expression of differentially expressed genes (DEGs) to observe the cellular events induced by changes in calcium concentrations. Intriguingly, DEG analysis revealed that the phosphatidylinositol-specific phospholipase C (PI-PLC) gene was upregulated and coccolith production by cells was blocked by the PI-PLC inhibitor U73122 under conditions closely associated with calcium-induced calcification. These findings imply that PI-PLC plays an important role in the biomineralization process of the coccolithophore E. huxleyi.

Gephyrocapsa huxleyi (Emiliania huxleyi) as a model system for coccolithophore biology

“…The availability of the G. huxleyi genome has facilitated the application of a range of omic technologies. Transcriptomic studies include examination of the cellular responses to nitrogen starvation and identification of calcification-related mechanisms through the manipulation of seawater calcium concentrations (Nam et al, 2020;Rokitta et al, 2014). An exciting development is the application of single-cell RNA-seq, which was used to profile transcriptomes from individual G. huxleyi cells throughout the viral infection cycle (Ku et al, 2020).…”

Recent development in ecdysone receptor of crustaceans: current knowledge and future applications in crustacean aquaculture

“…For example, the presence of N-terminus motif 19 known as glutamine-rich repeat motifs (GRR) found exclusively in the EcR domain of D. magna is linked with potential antiviral immunity in crustaceans (Palmer & Obbard 2016). Among the N-terminus motifs, motif 12 encodes the phosphatidylinositol-specific phospholipase C (PI-PLC), a family of intracellular enzymes involved in signal transduction and biomineralisation processes (Rend on-Ram ırez et al 2013; Nam et al 2020). Motif 13 and motif 20 are the putative phosphorylation sites of PKC and casein kinase II (CKII).…”

“…Among the N‐terminus motifs, motif 12 encodes the phosphatidylinositol‐specific phospholipase C (PI‐PLC), a family of intracellular enzymes involved in signal transduction and biomineralisation processes (Rendón‐Ramírez et al 2013; Nam et al 2020). Motif 13 and motif 20 are the putative phosphorylation sites of PKC and casein kinase II (CKII).…”