Oyster biomineralization under ocean acidification: From genes to shell

Area of Science:

• Marine biology
• Environmental science
• Molecular biology

Background:

• Ocean acidification (OA) significantly impacts marine calcifiers like oysters.
• Understanding molecular responses to OA is crucial for oyster conservation.
• The study focuses on Crassostrea hongkongensis, an important commercial oyster species.

Purpose of the Study:

• To investigate the influence of DNA methylation on gene expression in oyster mantle tissue under OA conditions.
• To determine if molecular changes induced by OA in the mantle are reflected in shell properties.
• To assess the resilience of C. hongkongensis to OA and its impact on biomineralization.

Main Methods:

• Culturing juvenile C. hongkongensis under control (~pH 8.0) and OA (~pH 7.4) conditions for 4.5 months.
• Analyzing DNA methylation and gene expression patterns in mantle tissue.
• Evaluating shell microstructure, crystal orientation, and hardness.

Main Results:

• Oysters exhibited moderate resilience to OA, maintaining shell growth rate, hardness, and crystal orientation.
• Expression of key biomineralization genes (carbonic anhydrase, alkaline phosphatase) remained unaffected.
• Increased expression of Ca2+ binding/signalling genes was observed in the mantle under OA.

Conclusions:

• Higher expression of Ca2+ binding/signalling genes is vital for maintaining biomineralization under OA.
• DNA methylation changes occur in response to OA but do not directly regulate gene expression in this context.
• For resilient oyster species, OA poses a greater 'dissolution problem' than a 'biomineralization problem'.