Temperature elevation and acidification damage microstructure of abalone via expression change of crystal induction genes

Ocean warming and acidification caused by global climate change interferes with the shell growth of mollusks. In abalone Haliotis discus hannai, the microstructural changes in the shell under stress are unclear, and the effect of thermal stress on biomineralization is unknown. The lack of gene information has also hampered the study of abalone biomineralization mechanisms. In this study, the microstructure of reconstructed shell in H. discus hannai was observed to determine the effects of thermal and acidification stress on shell growth. Three nacre protein genes, Hdh-AP7, Hdh-AP24, and Hdh-perlustrin, were characterized, and their expression pattern during shell repair was measured under thermal and acidification stress and compared with those of two known biomineralization-related genes, Hdh-AP-1 and Hdh-defensin. The stress resulted in aragonite plates with corroded or irregular microstructures. The gene expression of two nacre proteins (Hdh-AP7 and Hdh-AP24), which directly induce crystal formation, were more sensitive to thermal stress than to acidification, but the expression of the regulatory nacre protein (Hdh-perlustrin) and the two known genes (Hdh-AP-1 and Hdh-defensin), which are also related to immunity, showed an interlinked, complex pattern change. We concluded that high temperature and acidification damages the shell microstructure by disturbing the expression pattern of biomineralization-related genes.