Genome-Wide Analysis Reveals Expansion and Positive Selection of Monocarboxylate Transporter Genes Linked to Enhanced Salinity and Ammonia Tolerance in .

Our previous genome analysis of revealed an expansion of the monocarboxylate transporter gene family, which is crucial for metabolic dynamic balance and intracellular pH regulation. To further elucidate the role of these expanded genes in response to variable environmental conditions, we conducted a comprehensive genome-wide identification, phylogenetic evolution and expression analysis. In this study, 16 sodium-coupled monocarboxylate transporter genes (designated as ) and 54 proton-coupled monocarboxylate transporter genes (designated as ) were identified from the genome. The results of gene number comparison indicated significant expansion of and in mollusks compared to vertebrates, likely due to tandem repeats and dispersed duplications in . The syntenic analysis demonstrated that the razor-clam genes had the highest number of homologous gene pairs with . The phylogenetic tree showed that and proteins were distinctly clustered in two large branches. Moreover, positive selection analysis revealed three positive selection sites in the amino acid sequences sites. Multi-transcriptome analyses and the temporal expression patterns displayed that and play distinct roles in response to salinity and ammonia stressors. It is worth noting that the majority of these genes involved in abiotic stresses belong to . Overall, our findings revealed the important roles of and under abiotic stress, and provided valuable information for the evolution of this family in mollusks, as well as a theoretical basis for the further study of the mechanism and function of this gene family in .