Genome-Wide Identification and Characterization of the Carbonic Anhydrase Gene Family Reveals Carbonate Alkalinity Adaptability in Chinese Mitten Crab (<i>Eriocheir sinensis</i>)

Carbonic anhydrase (CA) is an essential zinc metalloenzyme that plays a crucial role in the physiological process of acid-base regulation in aquatic species. The CA gene family has been characterized in multiple species, but a comprehensive analysis of the CA gene family in Eriocheir sinensis is yet to be conducted. In this study, we identified members of the CA gene family from the E. sinensis genome and analyzed their genomic physical distribution, structural characteristics, expression patterns, and cellular localization. The results revealed a total of 15 CA genes in E. sinensis, distributed across 12 chromosomes, with tandem duplication observed on chr43. Phylogenetic analysis indicated that the 39 CA genes from E. sinensis, Procambarus clarkii, and Portunus trituberculatus can be classified into 4 clades and 11 subclades, with events of gene duplication and loss observed. Transcriptome expression analysis suggested that the EsiCA7 gene might play a dominant role in the acid-base regulation of E. sinensis. Furthermore, subcellular localization experiments for the EsiCA1 and EsiCA7 genes confirmed the predictions made by bioinformatics analysis. In conclusion, this study provides a theoretical basis and molecular targets for further research on the function of the CA gene family and the mechanism of alkalinity tolerance in E. sinensis.