A newly identified homolog of scallop caspase-3/7 plays a pivotal role in the immunological response and orchestrates the induction of apoptosis

Abstract

Chlamys farreri, commonly known as the Zhikong scallop, holds considerable value in global mariculture due to its economic importance. However, diseases pose a major threat to the scallop aquaculture industry. Thus, investigating the innate immune mechanisms of scallops, including the apoptosis mechanism, holds significant importance for the prevention and control of diseases. In this study, an executioner Caspase gene was isolated from the Zhikong scallop (Cf-Caspase-3/7-1), and its functional characteristics were explored. The complete open reading frame of Cf-Caspase-3/7-1 is 1698 base pairs in length, encoding a polypeptide composed of 566 amino acids. The analysis of the protein function domain revealed the existence of a conserved Caspase catalytic domain (CASc) in the C-terminal of Cf-Caspase-3/7-1. Phylogenetic analysis confirmed that Cf-Caspase-3/7-1 belongs to the molluscan Caspase-3/7 subfamily. qRT-PCR analysis showed that Cf-Caspase-3/7-1 mRNA is expressed in all the tissues investigated, with the highest transcript abundance observed in the gills. Additionally, its expression was mainly caused by various pathogenic molecular patterns, including lipopolysaccharide, polyinosinic: polycytidylic acid, peptidoglycan, and the acute viral necrosis virus. Overexpression of Cf-Caspase-3/7-1 in HEK293T cells induced dose-dependent NF-κB reporter genes activation and apoptosis, as shown by distinct morphological changes and increased Caspase-3/7 activity. Our findings provide a new perspective on the mechanism of action of the Caspase gene in mollusks and facilitate the advancement of comparative immunology as well as the sustainable development of the scallop aquaculture industry.