N -Acetyl-d-Glucosamine-Binding Lectin in Acropora tenuis Attracts Specific Symbiodiniaceae Cell Culture Strains.

Many corals establish symbiosis with Symbiodiniaceae cells from surrounding environments, but very few Symbiodiniaceae cells exist in the water column. Given that the -acetyl-d-glucosamine-binding lectin ActL attracts Symbiodiniaceae cells, we hypothesized that corals must attract Symbiodiniaceae cells using ActL to acquire them. Anti-ActL antibody inhibited acquisition of Symbiodiniaceae cells, and rearing seawater for juvenile contained ActL, suggesting that juvenile discharge ActL to attract these cells. Among eight Symbiodiniaceae cultured strains, ActL attracted NBRC102920 () most strongly followed by CS-161 (), CCMP2556 (), and CCMP1633 ( sp.); however, it did not attract GTP-A6-Sy (), CCMP421 (), FKM0207 ( sp.), and CS-156 ( sp.). Juvenile polyps of acquired limited Symbiodiniaceae cell strains, and the number of acquired Symbiodiniaceae cells in a polyp also differed from each other. The number of Symbiodiniaceae cells acquired by juvenile polyps of was correlated with the ActL chemotactic activity. Thus, ActL could be used to attract select Symbiodiniaceae cells and help Symbiodiniaceae cell acquisition in juvenile polyps of , facilitating establishment of symbiosis between and Symbiodiniaceae cells.