The role of Smad6 in immunity of the pearl oyster Pinctada fucata martensii

Inhibitory Smads (I-Smads), which belong to the Smad family and inhibit bone morphogenic protein 2 (BMP2) signaling by a variety of mechanisms, can suppress innate immunity responses in vertebrates. However, there are no reports for the role of Smad6 in immunity in mollusks. In this study, we showed that Smad6 of the pearl oyster Pinctada fucata martensii was located in the Smad6 cluster of the phylogenetic tree; mRNA expression of Smad6 and Smad3 was up-regulated after lipopolysaccharide and polyinosinic: polycytidylic challenge; and transcript levels of Smad6 and Smad3 showed opposite patterns during wound healing. Under salinity stress, water inflow and outflow in the gills appear to be regulated by BMP2-Smads signals, and BMP2-Smads signaling may be closely related to the immune response. Our results indicate that Smad6 is involved in immunity, that it plays a positive role in the response to immune challenge and an inhibitory role during wound healing, and that Smad6 and Smad3 may work against each other.

Automated summary

The study showed that Smad6 in mollusks, specifically in the pearl oyster Pinctada fucata martensii, plays a role in immunity. It has a positive effect in the immune response to challenges, but inhibits the wound healing process. Smad6 and Smad3 may have opposing functions.