Effects of pCO2 stress on gene expression and biomineralization of developing larvae of the Pacific oyster Crassostrea gigas

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The high larval mortalities in oyster hatcheries on the US west coast have gotten large media coveragein the past few years, and the link has been made between occurrences of coastal upwelling of deepwater with low carbonate ion availability and abnormal shell formation in hatchery larvae. However,the mechanism by which this happens is still not well understood. In the Pacific oyster, numerousgenes are known to be involved in biomineralization but little is known about the timing of geneexpression in relation to formation of the initial larval shell. In order to study this process, we scannedall expressed larval genes using an RNA-Seq approach over the time interval of initial shell formationin both control and pCO2-stressed conditions. Scanning the expression data for patterns matchingobserved shell formation rates, we identified a number of genes potentially involved in shellnucleation, most of which are involved in transmembrane transport or protein binding. In addition,we also identified a set of 149 co-expressed genes likely to be involved in the cellular early shellformation machinery.