Functional characterization of a molluscan executioner caspase in apoptosis and innate immunity

The Zhikong scallop (Chlamys farreri) is an economically important mollusk widely cultivated in marine aquaculture worldwide. However, the substantial threat posed by diseases to the scallop aquaculture industry necessitates an urgent investigation into innate immunity mechanisms, including apoptosis, in C. farreri. In this study, the scallop executioner caspase gene, Cf-caspase-3/7, was successfully cloned and its functional characteristics were explored. The results demonstrated that Cf-caspase-3/7 encodes 343 amino acids and contains the highly conserved caspase catalytic domain. Phylogenetic analysis confirmed that Cf-caspase-3/7 belongs to the molluscan executioner caspase family. The basic expression patterns analysis showed that Cf-caspase-3/7 is present in all scallop tissues, with the highest expression detected in the gonadal tissue. The Cf-caspase-3/7 protein was primarily found within the cytoplasmic compartment. Furthermore, the upregulated expression of Cf-caspase-3/7 in response to various pathogen-associated molecular patterns, including poly (I:C), peptidoglycan, and lipopolysaccharide, as well as its dose-dependent activation of the reporter genes for NF-κB and IFNβ, points to a possible function in regulating the scallops' innate immune response. HEK293T cells showed significant apoptotic characteristics and substantially elevated caspase-3 activity after transfection with the Cf-caspase-3/7 protein expression plasmid, highlighting the ability of Cf-caspase-3/7 to trigger apoptosis. In summary, these results provide a theoretical foundation for breeding disease-resistant scallops in aquaculture and deepen our knowledge of the functional significance of caspase genes in mollusks.