Effects of pCO2 stress on gene expression and biomineralization of developing larvae of the Pacific oyster Crassostrea gigas.
Pierre De Wit1, Evan Durland2, Alexander Ventura1, George Gerard Waldbusser3 and Christopher J Langdon2, (1)University of Gothenburg, Gothenburg, Sweden, (2)Oregon State University, Department of Fisheries and Wildlife, Newport, OR, United States, (3)Oregon State University, College of Ocean, Earth and Atmospheric Sciences, Corvallis, OR, United States
Abstract:
The high larval mortalities in oyster hatcheries on the US west coast have gotten large media coverage in the past few years, and the link has been made between occurrences of coastal upwelling of deep water 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, numerous genes are known to be involved in biomineralization but little is known about the timing of gene expression in relation to formation of the initial larval shell. In order to study this process, we scanned all expressed larval genes using an RNA-Seq approach over the time interval of initial shell formation in both control and
pCO
2-stressed conditions. Scanning the expression data for patterns matching observed shell formation rates (see Fig 1), we identified a number of genes potentially involved in shell nucleation, most of which are involved in transmembrane transport or protein binding. In addition, we also identified a set of co-expressed genes likely to be involved in the cellular early shell formation machinery.
This study is the first to investigate the genes involved in the initial larval shell formation in the Pacific oyster. We discover a set of 149 genes that are likely involved in this process from a combination of CPL microscopy and RNA-Seq, most of which are involved in ion transport or protein binding. These are the two main processes involved in shell formation. Additionally, we observe an increase in the relative content of wax esters in control larvae after 18 hours, something not seen in the treatment larvae. The reason for this is not quite clear at this point, but it could be speculated that stressed larvae develop slower, thus consuming lipids at a slower rate. Thus, follow-up experiments that study the long-term effects of changed carbonate chemistry on the genetics of Pacific oysters will be critical for future aquaculture efforts.
