Genome-wide identification and expression analysis of the CA gene family in brown algae Saccharina sculpera

Carbonic anhydrases (CAs) are zinc metalloenzymes that are ubiquitously distributed in nature and play important roles in the growth and development of diverse organisms. Although CAs have been extensively studied in plants and some algae, the CA gene family of Saccharina sculpera, an economically important seaweed, remains largely unexplored.

In this study, the 18 identified CA genes were distributed on 7 chromosomes in the genome of S. sculpera, and classified into α-, β-, and γ-subfamilies.

Physicochemical properties and subcellular localization analysis revealed that these CAs were hydrophilic, acidic and unstable proteins, primarily localized to chloroplasts and mitochondria. Gene structure analysis demonstrated that CA genes share similar characteristics within the same subfamily, while collinearity analysis revealed that tandem duplication is the primary mechanism driving CA gene family expansion. Additionally, a close phylogenetic relationship was found between the CA genes of S. sculpera and Saccharina japonica. Promoter cis-element analysis indicated that light is the dominant regulatory factor. Furthermore, RT-qPCR revealed distinct temporal variation in CA gene expressions, with most genes (SscCA2/4/6/7/11-18) decreasing initially then rising and the remaining (SscCA3/5/8/9) declining continuously throughout the developmental stages. In addition, enzyme activity analysis showed that total CA activity gradually increased throughout the developmental stages.

This systematic study of the CA gene family provides a foundation for further investigations into the biological functions of CA genes in S. sculpera.