Elevated ammonium reduces the negative effect of heat stress on the stony coral Pocillopora damicornis

Climate change and environmental pollution have been threatening the survival of corals. In the present study, whole transcriptomes of the coral Pocillopora damicornis were sequenced under high temperature and elevated ammonium. After reads mapping and abundance estimation, differentially expressed genes were obtained in the Control/Heat, Control/Heat_NH4 and Heat/Heat_NH4 comparisons. Five overrepresented GO terms centering the tumor necrosis factor signaling pathway were noted for significantly upregulated genes in the Control/Heat and Control/Heat_NH4 comparisons. In addition, five GO terms related to apoptosis and cell death were overrepresented for significantly upregulated genes in the Control/Heat comparison but not in the Control/Heat_NH4 comparison. The expression level of 112 genes in these GO terms increased significantly in the Heat group, but only 44 genes showed the increase trend in the Heat_NH4 group. These results collectively suggested that elevated ammonium could reduce the negative effect of heat stress on the coral P. damicornis.