Sugar transporter genes in a Symbiodinium species: genome-wide identification, expression analysis, and implications for coral-zooxanthellae symbiosis under stress

Symbiodiniaceae are well-known for their symbiotic relationship with corals, in which they provide sugars to corals in exchange for compounds they required. Therefore, the sugar transport in Symbiodiniaceae is crucial for coral health and survival, especially in the background of global changes. In our study, we performed a genome-wide analysis of the sugar transporter (STP) gene family in Symbiodinium microadriaticum and examined the expression patterns of the identified genes under stresses. We found 22 SmSTP genes with the Sugar_tr domain, belonging to three different groups based on their evolutionary origins. The 22 SmSTP proteins showed variations in their physicochemical properties, exon–intron structures, protein domains, and motifs, but all had transmembrane localization. Moreover, 10 SmSTP genes were differentially expressed under various stress conditions. This is the first study to identify and characterize STPs in Symbiodiniaceae, shedding light on their potential roles in the cnidarian-Symbiodiniaceae symbiosis and its adaptation to global changes.