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 <i>CA</i> gene family has been characterized in multiple species, but a comprehensive analysis of the <i>CA</i> gene family in <i>Eriocheir sinensis</i> is yet to be conducted. In this study, we identified members of the <i>CA</i> gene family from the <i>E. sinensis</i> genome and analyzed their genomic physical distribution, structural characteristics, expression patterns, and cellular localization. The results revealed a total of 15 <i>CA</i> genes in <i>E. sinensis</i>, distributed across 12 chromosomes, with tandem duplication observed on chr43. Phylogenetic analysis indicated that the 39 <i>CA</i> genes from <i>E. sinensis</i>, <i>Procambarus clarkii</i>, and <i>Portunus trituberculatus</i> can be classified into 4 clades and 11 subclades, with events of gene duplication and loss observed. Transcriptome expression analysis suggested that the <i>EsiCA7</i> gene might play a dominant role in the acid-base regulation of <i>E. sinensis</i>. Furthermore, subcellular localization experiments for the <i>EsiCA1</i> and <i>EsiCA7</i> 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<i> CA</i> gene family and the mechanism of alkalinity tolerance in <i>E. sinensis</i>.