Genes related to ion-transport and energy production are upregulated in response to CO2-driven pH decrease in corals:...

Area of Science:

• Marine Biology
• Oceanography
• Molecular Biology

Background:

• Ocean surface pH has decreased by 0.1 units since preindustrial times, projected to drop further by 2100.
• Decreasing pH affects seawater saturation state, impacting calcifying organisms like scleractinian corals, key reef builders.
• Few studies have explored the global molecular impact of low pH on corals.

Purpose of the Study:

• Investigate global transcriptomic modifications in Pocillopora damicornis under low pH conditions.
• Identify molecular mechanisms and biological functions affected by ocean acidification in corals.
• Understand the link between pH levels and gene expression related to coral physiology.

Main Methods:

• RNA sequencing (RNAseq) to analyze global transcriptomic changes in corals exposed to pH 7.4 vs. pH 8.1 for 3 weeks.
• Quantitative reverse transcription PCR (q-RT-PCR) to validate transcript abundance of 48 candidate genes.
• Exposure of corals to pH 7.2 and 7.8 for 3 weeks for q-RT-PCR validation.

Main Results:

• 16% of the coral transcriptome was affected by low pH treatment (6% upregulated, 10% downregulated).
• Low pH (≥7.4) upregulated genes involved in calcium/carbonate transport, CO2 conversion, and organic matrix formation, supporting calcification.
• Upregulation of genes related to heterotrophic and autotrophic processes suggests increased energy demands and mobilization of reserves.

Conclusions:

• Ocean acidification at pH ≥7.4 stimulates gene expression supporting calcification and energy metabolism in Pocillopora damicornis.
• Uncoordinated downregulations may indicate a trade-off mechanism for energy reallocation under stress.
• Findings highlight the complex molecular responses of corals to changing ocean pH.